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hal-04798150 | Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing | Luc Froehly|Mostafa Hassan|Valeria Viviana Belloni|Rémi Meyer|Luca Furfaro|Remo Giust|François Courvoisier | 2024 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Physique; Sciences de l'ingénieur | HAL | 1 | <figure><img src="image_1.png" /></figure>
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# Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing
Luc Froehly, Mostafa Hassan, Valeria Viviana Belloni, Rémi Meyer, Luca Furfaro, Remo Giust, François Courvoisier
► To cite this version:
Luc Froehly, Mostafa Hassan, Valeria Viviana Belloni, Rémi Meyer, Luca Furfaro, et al.. Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing. SPIE Optical Systems Design, Apr 2024, Strasbourg, France. hal-04798150
HAL Id: hal-04798150
https://hal.science/hal-04798150v1
Submitted on 22 Nov 2024
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abroad, or from public or private research centers.
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hal-04798150 | Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing | Luc Froehly|Mostafa Hassan|Valeria Viviana Belloni|Rémi Meyer|Luca Furfaro|Remo Giust|François Courvoisier | 2024 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Physique; Sciences de l'ingénieur | HAL | 2 | # Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing
L. Froehly, M. Hassan, V. Belloni, R. Meyer, L. Furfaro, R. Giust, and F. Courvoisier
Institut FEMTO-ST, Université de Franche-Comté CNRS UMR 6174,
25000 Besançon, France
## ABSTRACT
Bessel beams, known for maintaining focus over long distances, find many applications in imaging, nonlinear optics and laser material processing. For these applications, generating sub-micrometer Bessel beams is essential, but requires complex optical systems. Traditional optical software, designed for ray tracing, are challenged for this task. Here we show how we can use optical software to create and optimize optical design to generate these unconventional beams. The research involves high numerical aperture systems, investigates the influence of polarization, and the use of diffractive optical elements. Numerical findings are compared to experimental results, highlighting the potential of software-assisted beam design for various applications.
**Keywords:** Bessel beams, Laser ablation, optical system, ZEMAX OpticStudio@ANSYS
## 1. INTRODUCTION
Bessel beams are propagation-invariant solutions to the Helmholtz equation and have the unique property of maintaining a focus over distances significantly larger than Gaussian beams of the same diameter$^{1,2}$. This characteristic makes Bessel beams highly advantageous for applications such as imaging$^{3}$ and laser nano-ablation$^{4}$. Complex imaging systems with multiple lenses are required to generate such beams$^{5}$. In this context, properly accounting for aberrations is crucial to designing high spatial resolution systems. This calculation quickly becomes complex, necessitating the use of software simulating optical systems. However, these programs were originally designed for conventional imaging problems and rely primarily on ray-tracing approximations. We demonstrate the potential benefits of utilizing software to aid in creating non-traditional beams. We will provide an overview of the design and optimization of various optical systems to generate Bessel beams, where we designed large numerical aperture systems or used diffractive optical elements. Our numerical results are compared to experimental results obtained in several projects.
## 2. OPTIMIZATION WITH THE STREHL RATIO
Generating Bessel beams with micrometer or sub-micrometer lateral dimensions typically requires complex optical systems with many components. Designing, optimizing, and aligning such systems can be challenging without specialized optical design software. ZEMAX OpticStudio@ANSYS (ZOS) is one of the most widely used software packages in academia. The software offers strong optimization capabilities, a range of components and material libraries, and various analysis tools, including the Strehl ratio$^{6}$. This ratio assesses the imaging quality of an optical system by comparing the peak intensity of the actual point source image to the theoretical peak intensity when diffraction-limited. Although originally intended for classical imaging systems, this method can be adapted for use in ZOS to optimize and simulate Bessel beam profiles, which result from an interference, with a high degree of precision.
## 3. EXAMPLES OF SYSTEMS DEVELOPED USING ZOS.
This section presents examples where the use of ZOS was crucial in designing and optimizing Bessel beam generation setups. The section is divided into two main directions: optimizing setups to find suitable components and simulating specific behaviors. | 494 | Ingénierie et technologie | |
hal-04798150 | Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing | Luc Froehly|Mostafa Hassan|Valeria Viviana Belloni|Rémi Meyer|Luca Furfaro|Remo Giust|François Courvoisier | 2024 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Physique; Sciences de l'ingénieur | HAL | 3 | ## 3.1 Design and Optimization of Setup
There are some applications of Bessel beams that require very high intensity in the central core of the beam, such as materials processing. Many interesting configurations have been proposed in the literature that produce central core dimensions that can be as low as 0.36λ. In general, all these techniques result in highly extended systems, high risk of damage to expensive components and are limited to relatively low focusing or cone angles. We have recently proposed a design that overcomes these limitations⁵. The core of our system is the coupling between a low angle axicon and a hemispherical lens. The correct design of the setup and subsequent component selection and simulation was only made possible by using ZOS.
<figure><img src="image_2.png" /><figcaption>Figure 1. The generation of high NA Bessel beams. The setup is shown at the top, while the sections of the Bessel beams are shown at the bottom, including a comparison between the simulations obtained with ZOS (top line) and the experimental results (bottom line). Columns: (a) The Bessel beam is undisturbed, (b) the axicon is tilted by 0.14°, (c) a 50µm shift of the half-ball lens is introduced. The scale bars represent 2µm.</figcaption></figure>
As can be seen in Fig.1, the first low angle axicon is a reflective off-axis axicon from Canunda (Canunda axicon AX-2-25-S). The axicon was simulated and optimised using a biconic surface type in the Sequential Lens Data Editor. The results shown in Fig. 1 show excellent agreement with the experimental validations, even under different misalignment conditions.
## 3.2 Simulation of Specific System Properties
In 2019, we conducted a comprehensive review of various achievements that showcase the use of Fourier transform and transfer functions in optics. These applications have led to remarkable advances in unconventional areas of optics, particularly in the spatial manipulation of complicated laser beams in terms of both their amplitude and | 313 | Ingénierie et technologie | |
hal-04798150 | Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing | Luc Froehly|Mostafa Hassan|Valeria Viviana Belloni|Rémi Meyer|Luca Furfaro|Remo Giust|François Courvoisier | 2024 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Physique; Sciences de l'ingénieur | HAL | 4 | phase characteristics. In particular, we have shown that it is possible to generate an achromatic Bessel beam with a central lobe diameter of 10µm FWHM, propagating over 7mm, and with a spectral bandwidth of more than 200 nm. An achromatic Bessel beam was generated using a spatial light modulator due to its diffractive nature. It is worth noting that a classical refractive axicon is unable to produce this type of beam⁷. Wide band
<figure><img src="image_3.png" /><figcaption>Figure 2. Simulations using ZOS to generate wide-band Bessel beam profiles with a bandwidth of 400nm. The beam structure (A) and its cross-section (C) were obtained using a diffractive axicon. The cross-section was taken along the dotted line (cs). The beam structure (B) and its cross-section (D) were obtained using a refractive axicon. The cross-section was taken along the dotted line (cs).</figcaption></figure>
Bessel beams were simulated using ZOS (Fig. 2). The results show that the achromaticity of diffractive axicons was retrieved as expected. However, in the case of the refractive axicon (Fig. 2(B)), the Bessel beam lobes are blurred as predicted too. To generate a diffractive axicon, we utilized the 'Optically Fabricated Hologram' surface type in the sequential lens data editor.
## 4. CONCLUSION
Designing and optimizing complex optical systems is necessary for generating high numerical aperture Bessel beams. Software such as ZOS can simplify this process. The results obtained through this method have been validated experimentally and are in excellent agreement. The Strehl ratio is a key optimization criterion for these models and can be used under certain conditions beyond conventional beams. The use of optical calculation software for Bessel beams enables the design and optimization of more complex systems in the future. | 279 | Ingénierie et technologie | |
hal-04798150 | Optical Software-Assisted Design and Optimization of Bessel Beam Systems for applications to laser materials processing | Luc Froehly|Mostafa Hassan|Valeria Viviana Belloni|Rémi Meyer|Luca Furfaro|Remo Giust|François Courvoisier | 2024 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Physique; Sciences de l'ingénieur | HAL | 5 | ACKNOWLEDGMENTS
This project has received funding from H2020 European Research Council (ERC) under grant agreement 682032-PULSAR, the European Union's Horizon 2020 research and innovation program under grant agreement No 825246 kW-flexiburst, the French Agence Nationale de la Recherche, projects DENSE (ANR-21-CE08-0005) and EQUIPEX+ SMARTLIGHT platform (ANR-21-ESRE-0040), and the EIPHI Graduate School (ANR-17-EURE-0002). This work was partially supported by the French Renatech network.
REFERENCES
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hal-03028549 | La pédopsychiatrie en souffrance | Isabelle Coutant | 2020 | fr | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Sciences humaines et sociales | HAL | 1 | La pédopsychiatrie en souffrance
Isabelle Coutant
► To cite this version:
Isabelle Coutant. La pédopsychiatrie en souffrance. Savoir/Agir, 2020, Politisation, dépolitisation et repolitisation de la crise sans fin de la psychiatrie publique, 52, pp.79-83. hal-03028549
HAL Id: hal-03028549
https://hal.science/hal-03028549v1
Submitted on 10 Dec 2020
HAL is a multi-disciplinary open access
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lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
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<figure><img src="image_1.png" /></figure>
HAL Authorization | 129 | Sciences médicales et de la santé | |
hal-03028549 | La pédopsychiatrie en souffrance | Isabelle Coutant | 2020 | fr | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Sciences humaines et sociales | HAL | 2 | # La pédopsychiatrie en souffrance
Isabelle Coutant, sociologue, CNRS-Iris
La souffrance adolescente est devenue un enjeu des politiques publiques à partir des années 1990. Les institutions ont été incitées à développer des accueils spécifiques pour les adolescents, et les points écoute jeunes, puis les Maisons des adolescents se sont multipliés sur le territoire. Cette politique s'est développée au confluent d'une préoccupation à la fois morale (prévenir le suicide) et d'ordre social (les violences urbaines, et plus récemment la « radicalisation », étant interprétées comme symptôme de souffrance). Dans le même temps, les files d'attente auprès des CMP, ou pour des lits d'hospitalisation se sont allongées, les moyens humains en pédopsychiatrie n'augmentant pas à la hauteur d'une demande de soins en forte croissance.<fnref n="1" /> Cette augmentation de la demande de soins tient sans doute aux effets de la dégradation des conditions de vie dans les territoires les plus déshérités, mais aussi à des transformations sociales plus générales propices aux dépressions, aux addictions et aux pathologies « limite », tous milieux sociaux confondus.<fnref n="2" /> Elle s'explique aussi probablement par une préoccupation plus grande des adultes envers les troubles des enfants et des adolescents qui les amènent à solliciter les structures de soins plus fréquemment qu'auparavant, et, dans le cas des jeunes les plus démunis, par les difficultés que rencontrent les autres institutions d'encadrement de la jeunesse pour s'acquitter de leurs missions. La pédopsychiatrie vient alors faire office de soupape pour les autres institutions. C'est dans ce contexte qu'elle est notamment amenée à prendre en charge les « troubles du comportement », les « troubles de conduites » ou pathologies « border line » d'adolescents « difficiles » - les qualifications diffèrent selon les nosographies et les affiliations théoriques.<fnref n="3" />
Comment la pédopsychiatrie fait-elle face ? A quelles conditions peut-elle « bien travailler » ? Les moyens institutionnels sont inégalement répartis sur le territoire, certains départements étant nettement mieux pourvus que d'autres. La répartition des moyens n'est pas toujours proportionnelle aux besoins de la population, et notamment à sa démographie. C'est l'argument qui a été mobilisé par une équipe de pédopsychiatres dans un secteur défavorisé de la région parisienne pour obtenir la création d'une unité d'hospitalisation temps plein pour adolescents à la fin des années 1990, la courbe de la fermeture des lits depuis l'après-guerre ayant connu une évolution inversée de celle de sa dynamique démographique. Compte-tenu des caractéristiques du secteur, c'est en outre dans la prise en charge des « troubles du comportement » que cette unité s'est spécialisée, pour des jeunes âgés de 12 à 18 ans. En tant que sociologue ethnographe, c'est l'activité de cette unité que j'ai étudiée, à la fin des années 2000 : pendant neuf mois, j'ai passé en moyenne trois jours par semaine dans le service qui comportait dix lits d'hospitalisation et un centre de jour, assisté aux réunions, aux entretiens quand les professionnels, les patients et les familles donnaient leur accord. J'ai pu consulter les dossiers des jeunes suivis et me suis intéressée en profondeur à
<footnote n="1">¹ Voir le rapport du Sénat sur la psychiatrie des mineurs, déposé le 4 avril 2017 : https://www.senat.fr/rap/r16-494/r16-494.html</footnote>
<footnote n="2">² Alain Ehrenberg, *La fatigue d'être soi. Dépression et sociétés*, éditions Odile Jacob, Paris, 1998 ; Maurice Corcos, Claire Lamas, « Fonctionnements limites à l'adolescence : psychopathologie et clinique psychodynamique », *L'information psychiatrique*, vol. 92, n°1, janvier 2016, p. 15-22.</footnote>
<footnote n="3">³ Yannis Gansel, *Vulnérables ou dangereux ? Une anthropologie du souci des adolescents difficiles*, ENS Editions, Lyon, 2019.</footnote> | 583 | Sciences médicales et de la santé | |
hal-03028549 | La pédopsychiatrie en souffrance | Isabelle Coutant | 2020 | fr | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Sciences humaines et sociales | HAL | 3 | une trentaine de cas. J'ai assisté à quelques réunions avec d'autres institutions en dehors de l'hôpital. Et j'ai réalisé des entretiens avec une grande partie de l'équipe, tous grades confondus.<fnref n="4" />
Les psychiatres responsables de cette unité, âgés d'une soixantaine d'années au moment de l'enquête, se rattachaient à la psychiatrie institutionnelle. Ils étaient différemment imprégnés de psychanalyse, ne prescrivaient pas tous les mêmes doses de médicaments, mais ils avaient en commun de considérer l'ensemble de l'équipe comme un « outil thérapeutique », agents hospitaliers, aide-soignant(e)s et secrétaires inclus. C'est la raison pour laquelle, sans doute, le « petit personnel » garantissait une forme de stabilité à l'équipe, qui contrastait avec le fort turn over des jeunes infirmier(e)s, attiré(e)s par des services plus « techniques » et plus prestigieux. Pour les agents hospitaliers et les aide-soignant(e)s, les réticences initiales à l'affectation dans l'unité avaient rapidement été levées du fait de l'intérêt trouvé à y exercer : « On arrive ici par hasard, on y reste par choix » disait l'une d'elles ; « travailler ici, c'est plus valorisant qu'au Central – [la médecine somatique, dans le bâtiment principal] – parce qu'ici on reste pas au niveau des balais et des seaux », disait une autre. Les tâches les moins valorisantes, autour du ménage, étaient en partie partagées avec les infirmier(e)s, avec les éducatrices et les patients eux-mêmes ; et d'autres tâches, concernant la relation avec les adolescents ainsi que certaines activités thérapeutiques, leur étaient confiées. Le point de vue des agents hospitaliers et des aide-soignant(e)s était pris en compte pour évaluer l'évolution des patients, ils participaient aux réunions de transmission quotidiennes et aux réunions de synthèse hebdomadaires. L'instabilité de l'équipe infirmière était a contrario une préoccupation pour les psychiatres, le turn over étant préjudiciable à la qualité des soins. La vacance de postes infirmiers avait été résolue par le recrutement de médecins étrangers officiant comme infirmiers : ils représentaient, comme le « petit personnel », une stabilité rassurante, tant pour les patients que pour les soignants moins expérimentés. Eux-mêmes s'étaient formés à la pédopsychiatrie « sur le tas », en écoutant et en observant les collègues, apprenant des agents hospitaliers et des aide-soignant(e)s autant que des psychiatres. Ils devaient toutefois passer le concours d'infirmier au bout de trois années, et en cas d'échec, étaient rétrogradés comme aide-soignants, sans plus de considération pour la compétence accumulée au cours de leur formation passée et de leur activité présente.
Les personnels « de première ligne », quotidiennement au contact des patients, dans le quotidien de l'unité, pouvaient cependant se sentir incompris des professionnels « de seconde ligne », dont l'activité se déroulait en majeure partie dans des bureaux, à l'écart des lits d'hospitalisation. Infirmier(e)s, aide-soignant(e)s, agents hospitaliers, éducatrices, qui étaient amenés à faire rempart de leur corps lors des « clashs » pour contenir les adolescents, se sentaient parfois insuffisamment soutenus par les psychiatres et les psychologues, dans l'après-coup de tels événements. Dans l'ensemble, ils préféraient les protocoles bien balisés (par exemple tant de temps de chambre pour une insulte) plutôt que les injonctions à travailler « au feeling » qui les confrontaient à la peur de « mal faire », n'appréciaient pas toujours qu'on les amène à s'interroger sur leur responsabilité dans la survenue d'un « clash » quand les adolescents n'étaient pas eux-mêmes « repris », et trouvaient plus facile d'apprivoiser un jeune d'abord sédaté par un traitement médicamenteux, que de « travailler avec son symptôme » comme pouvaient le proposer les psychiatres et les psychologues. Une
<footnote n="4">⁴ Isabelle Coutant, *Troubles en psychiatrie. Enquête dans une unité pour adolescents*, La Dispute, Paris, 2012 ; « The psychiatric treatment of ‘behavioural problems’ in adolescence : Between coercion and socialisation », *Anthropology & Medicine*, vol. 23, 2016, p. 259-274.</footnote> | 627 | Sciences médicales et de la santé | |
hal-03028549 | La pédopsychiatrie en souffrance | Isabelle Coutant | 2020 | fr | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Sciences humaines et sociales | HAL | 4 | aide-soignante confiait ainsi, après avoir été agressée par une adolescente : « Même si tu sais qu'elle n'attaque pas l'individu mais le cadre, l'institution, tu te dis que tu travailles pour l'institution donc tu sers aux symptômes de cette jeune. En fait tu es la marionnette qui permet à la jeune de lâcher son symptôme, et comme cela on peut dire qu'elle attaque l'institution. Mais c'est quand même mon corps ! Quand un jeune t'attaque, on te dit que ce n'est pas toi la personne attaquée, mais en attendant, ton corps fait partie de toi quand même ! La peau, les cheveux, l'émotion, tu ne peux pas les mettre de côté en disant qu'il ne faut pas faire attention parce que c'est le cadre et l'institution. » Le psychiatre responsable de l'unité avait donc pour tâche d'arbitrer entre la compréhension due aux patients, et l'attention à porter aux soignants de « première ligne », afin d'assurer une stabilité d'équipe et une ambiance de travail favorables à un soin de qualité.
Ce qui était considéré comme du soin de qualité ou du « bon travail », reposait en grande partie sur le « travail de l'alliance » avec les patients et, avec leurs familles lorsqu'elles étaient présentes. L'enjeu était de construire le consentement au soin, notamment en justifiant la contrainte comme thérapeutique. Pour que cette justification soit efficace, il fallait que les soignants eux-mêmes soient convaincus de son bien-fondé et de la légitimité de leur intervention, ce qui n'allait pas toujours de soi face à des troubles qui n'étaient pas nécessairement très avérés dans la nosographie psychiatrique. D'où les tensions récurrentes avec les services éducatifs lorsqu'ils sollicitaient l'unité pour hospitaliser un(e) adolescent(e) qu'ils ne parvenaient pas à gérer : « Qu'est-ce qui vous fait penser qu'on va faire ça mieux que vous ? », leur renvoyaient régulièrement les psychiatres. Ces résistances à la demande tenaient aussi à l'inquiétude de voir ces hospitalisations excéder la durée jugée nécessaire aux soins, faute de solutions de placement en aval de l'hôpital dans certains cas, les adolescents hospitalisés souffrant du double stigmate « psychiatrie » et « banlieue » aux yeux des familles d'accueil ou des foyers susceptibles de les accueillir une fois la « crise » traitée. C'est ainsi qu'au cours de mon enquête, trois patients par ailleurs suivis par les services de l'aide sociale à l'enfance étaient hospitalisés depuis près d'un an, alors que les psychiatres les jugeaient « sortants » depuis plusieurs mois et qu'ils étaient scolarisés en journée dans des établissements spécialisés. Dans ces situations, les psychiatres redoutaient de se retrouver dans un « face-à-face » avec le patient, sans institutions tierces pouvant prémunir la psychiatrie de « la tentation totalitaire » qui a marqué son histoire - ce sont les termes qu'employait l'une des psychiatres.
Les psychiatres craignaient aussi la chronicisation d'adolescents qui finissaient par se représenter l'unité comme leur « deuxième maison », et qui, une fois sortis, demandaient parfois à être réhospitalisés, ce qui en disait long sur leurs conditions de vie en dehors de l'hôpital. Tout l'enjeu pour les soignants était alors de « travailler l'aval », « travailler l'insertion » : mais cela supposait des structures d'aval en quantité suffisante, ce qui n'était pas le cas au moment de l'enquête. Beaucoup s'inventait et se bricolait, grâce aux liens tissés au fil du temps avec différents professionnels de la région, dans différentes institutions : tel principal de collège, telle assistante sociale de secteur, telle famille d'accueil, tel lieu de vie, telle fondation soins-études... Il arrivait aussi que d'autres services de l'hôpital soient sollicités pour que des adolescents hospitalisés y effectuent des « stages », leurs capacités d'insertion et d'interaction pouvant être évaluées à cette occasion. Lorsque les adolescents retournaient vivre dans leurs familles, c'était un « travail des relations familiales » qui s'engageait, afin d'influer sur les relations et les perceptions mutuelles, de manière notamment à alléger l'adolescent du stigmate dont il était porteur. Il s'agissait d'introduire un mouvement sans | 663 | Sciences médicales et de la santé | |
hal-03028549 | La pédopsychiatrie en souffrance | Isabelle Coutant | 2020 | fr | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Sciences humaines et sociales | HAL | 5 | pour autant faire trop trembler l'édifice, tout en préservant « l'alliance » nécessaire à un suivi thérapeutique dans la durée afin de consolider ce qui avait été entrepris.
Toutes ces dimensions de l'activité thérapeutique, qui participent de ce que les soignants définissent comme « du bon travail », dont ils peuvent s'estimer satisfaits, reposent sur la parole et requièrent du temps. Elles ne sont pas aisément quantifiables et s'ajustent mal aux attendus administratifs qui président à l'évaluation de l'activité. Elles nécessitent du personnel, et des équipes relativement stables. Elles supposent des pédopsychiatres en nombre suffisant, à l'heure où la profession s'inquière de son vieillissement et de la vacance de postes à l'hôpital public. Dans une tribune publiée par *Libération* le 29 mars 2018, intitulée « La pédopsychiatrie ne veut pas mourir ! », les pédopsychiatres Bernard Golse et Marie-Rose Moro alertaient ainsi sur les perspectives de la pédopsychiatrie du fait du manque de moyens et de personnel. Ils notaient qu'en dix ans, alors même que l'activité avait fortement augmenté, le nombre de pédopsychiatres avait diminué de moitié, et que la grande majorité ayant plus de 55 ans, cette situation risquait de s'aggraver. Si les problèmes de recrutement tiennent à des paramètres multiples, il sont aussi le signe de la souffrance d'une profession sous tension.<fnref n="5" /> Lors de mon enquête, l'une des psychiatres de l'équipe affectée aux urgences pédiatriques souffla un jour de découragement : « Je rêve d'avoir une vraie bouffée délirante ». Manière indirecte de signifier la fatigue accumulée à traiter de situations chronophages dans lesquelles bien souvent souffrances sociales et psychiques s'entremêlent. Lorsque le psychiatre responsable de l'unité a quitté l'hôpital, suite à un conflit avec une administration qu'il jugeait de plus en plus intrusive, il n'a pas été remplacé, faute de candidat. Il a fallu réduire le nombre de lits, et déléguer un peu plus l'activité de consultations et de gestion d'équipe aux jeunes psychologues, pour la plupart en contrat précaire.
Sommée de « bien traiter » ses patients en les considérant comme des « sujets », de s'assurer le plus possible de leur « consentement » malgré la contrainte, de respecter leurs droits, de les accueillir tout en encourageant leur « autonomie », la pédopsychiatrie a vu, comme la psychiatrie, les exigences éthiques peser de plus en plus sur ses pratiques, alors même que ses missions se sont étendues à toute la gamme des souffrances sociales, dans un contexte de précarisation accrue tant de l'institution que d'une partie de son public. Injonctions parfois contradictoires que la pandémie de covid-19 est venue tout à la fois un peu plus révéler et accentuer.
<footnote n="5">⁵ Christian Baudelot, Michel Gollac et alii, *Travailler pour être heureux* ? Fayard, Paris, 2003.</footnote> | 452 | Sciences médicales et de la santé | |
cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 1 | <figure><img src="image_1.png" /></figure>
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# Synthesis and structure of a chiral areno-bridged
[2.4]metacyclophane
Thamina Akhter, Md. Monarul Islam, Taisuke Matsumoto, Junji Tanaka,
Pierre Thuéry, Carl Redshaw, Takehiko Yamato
► To cite this version:
Thamina Akhter, Md. Monarul Islam, Taisuke Matsumoto, Junji Tanaka, Pierre Thuéry, et al. Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane. Tetrahedron, 2018, 74, pp.329-335. 10.1016/j.tet.2017.11.075. cea-01656007
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cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 2 | # Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane
Thamina Aktherª, Md. Monarul Islamª,ᵇ, Taisuke Matsumotoᶜ, Junji Tanakaᶜ, Pierre Thuéryᵈ, Carl Redshawᵉ and Takehiko Yamatoª, ∗
ABSTRACT
The reductive coupling reaction of 1,4-bis(3-acetyl-5-tert-butyl-2-methoxyphenyl)butane 3 was carried out using TiCl4-Zn in pyridine followed by a McMurry
coupling reaction to afford the compounds anti and syn 1,2-dimethyl[2.4]MCP-1-ene 4. Bromination of 4 with BTMA-Br3 in dry CH2Cl2 afforded the interesting
compound 1,2-bis-(bromomethyl)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-1-ene 6 and consecutive debromination with Zn and AcOH in CH2Cl2 solution
afforded the stable solid 5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP 7 in 89% yield. Compound 7 was conveniently employed in a Diels-Alder
reaction with dimethyl acetylenedicarboxylate (DMAD) to provide 2-(3',6'-dihydrobenzo)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-4',5'-dimethylcarboxylate
8 in good yield. Diels-Alder adduct 8 was converted into a novel and inherently chiral areno-bridged compound [2.4]MCP 9 by aromatization. The chirality of
the two conformers was characterized by circular dichroism (CD) spectra of the separated enantiomer which are perfect mirror images of each other
Keywords: Metacyclophane; McMurry reaction; Bromination; Diels-Alder reaction; chirality
**1. Introduction**
Cyclophanes, cyclic molecules containing both aromatic and aliphatic regions, are a class of compound that are captivating the imagination of chemists.¹ Metacyclophanes (= MCP) have been known for approximately 75 years and various derivatives have been prepared and found to exhibit unique properties.² The cyclophanes with shorter carbon chains (n = 4–6) have captivated the inspiration of chemists as exemplary compounds for the molecular strain and bending of benzene rings.³ Synthetic and conformational analysis of this type of macrocyclic compounds was recently reported, with some researchers focusing on the formation of rigid structures by restricting the flexible conformations, thereby enabling these systems to act as platforms for diverse complexation experiments.⁴ Our interest in this field stems from observations on cyclic diynes having two double bonds as a part of the aromatic ring system.⁵
Raming and Gleiter reported the syntheses of [*n*]MCP-diynes and the conversion of propargylic into allenic moieties as well as reactions with strong bases.⁶ The bromination–dehydrobromination reactions of the corresponding [*2*,*n*]MCP–enes to strained [*2*,*n*]MCP–ynes possessing bent triple bonds was reported by Kawase and co-workers.⁷
For over three decades, the McMurry reaction and other Ti
based reductive couplings have been effectively applied to the
synthesis of cyclophanes. A one-step route to alkene-
containing cyclophanes is provided by the McMurry reaction
which also allows for the generation of moderately strained
cyclophanes.⁸⁻¹²
<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Possible conformations of areno-bridged [2.4]MCPs.</figcaption></figure>
Our research group has published a series of [2.n]MCPs utilizing McMurry coupling reactions, in which the aliphatic chain length ranged from 2 to 10. ¹³ Reports on the synthesis of chiral [2.n]MCPs which contain long carbon chains have yet to be published. Helical chirality is one type of chiral system that does not contain any stereogenic centers. ¹⁴⁻¹⁷
Very recently, we reported the synthesis and a conformational
study of the areno-bridged [2.10]MCP together with its chiral
properties, but we have not yet succeeded in the resolution of each
enantiomer, which we think is due to the flexible structure. ¹³f In
this paper, conformational studies of a number of shorter
methylene bridged [2.4]MCPs which can adopt anti- and syn-
conformations (as represented in Fig. 1), both in solution and the
solid state, are described. We also report the first successful
synthesis and resolution of each enantiomer of the novel chiral
[2.4]MCP containing an areno-bridge and a brief discussion about
its inherent chirality.
<footnote>ª Department of Applied Chemistry, Faculty of Science and Engineering, Saga University, Honjo-machi 1, Saga 840-8502 Japan, E-mail: yamatot@cc.saga-u.ac.jp</footnote>
<footnote>ᵇChemical Research Division, Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhanmondi, Dhaka-1205, Bangladesh</footnote>
<footnote>ᶜInstitute of Materials Chemistry and Engineering, Kyushu University, 6-1, Kasugakoen, Kasuga 816-8580, Japan</footnote>
<footnote>ᵈNIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France</footnote>
<footnote>Department of Chemistry, School of Mathematics and Physical Sciences, The University of Hull, Cottingham Road, Hull, Yorkshire, HU6 7RX, UK</footnote> | 628 | Sciences naturelles |
cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 3 | ## 2. Results and discussion
The starting compound 1,4-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)butane **1** was easily prepared from 1,4-bis(5-tert-butyl-2-methoxyphenyl)butane according to the reported procedure.13,18,19 In the presence of dichloromethyl ether and titanium tetrachloride (TiCl₄), a regioselective Friedel-Crafts acylation reaction20, 21 at the *meta* position of 1,4-bis(5-tert-butyl-2-methoxyphenyl)butane was achieved at room temperature to afford **1** in 68% yield. To a solution of methylmagnesium iodide in Et₂O was added dropwise a solution of compound **1** in tetrahydrofuran (THF) under relatively mild conditions (refluxing for 12 h). The product afforded was 1,4-bis(5-tert-butyl-3-(1-hydroxyethyl)-2-methoxyphenyl)-butane **2** in 95% yield.
<figure><img src="image_3.png" /><figcaption>**Scheme 1** Synthesis of 1,4-bis(3-acetyl-5-tert-butyl-2-methoxyphenyl)butane **3**.</figcaption></figure>
Oxidation²² of compound **2** was carried out in acetone by dropwise addition to a solution of pyridinium chlorochromate (PCC) in acetone and stirring at room temperature for 24 h; 1,4-bis(3-acetyl-5-tert-butyl-2-methoxyphenyl)butane **3** was isolated in 74% yield as shown in Scheme 1.²³, ²⁴ Elemental analysis and spectral data were used to resolve the structures of compounds **2** and **3**. Furthermore, the ¹H NMR spectroscopic signals of **2** and **3** were also unambiguously assigned.
<figure><img src="image_4.png" /><figcaption>**Scheme 2** Synthesis of anti- and syn-5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethyl[2.4]MCP-1-ene **4**.</figcaption></figure>
Compound **3** was further subjected to reductive coupling by following the McMurry reaction through the upgraded Grützmacher's procedure (Scheme 2).¹² Thus, the reductive coupling reaction of **3** was carried out by using TiCl₄-Zn in the presence of pyridine in refluxing THF under high dilution conditions to afford the required compounds *anti-* and *syn*-5,15-di-*tert*-butyl-8,18-dimethoxy-1,2-dimethyl[2.4]MCP-1-ene **4** in 30 and 14% yields, respectively. This result was different from that of the related McMurry cyclization of 1,3-bis(5-acetyl-2-methoxyphenyl)propane **3**, which provided the identical [3.1]MCP when using TiCl₄ or an acid induced pinacol rearrangement reaction.²⁵
The structure of **4** was elucidated based on elemental analyses and spectral data. The mass spectral data for **4** (M⁺ = 434.65) fully support the cyclic structure. The conformation of **4** was clear from the ¹H NMR spectrum. The ¹H NMR spectrum of *anti*-4 in CDCl₃ exhibits a singlet at δ 3.24 ppm
for the methoxy protons, a singlet at δ 1.32 ppm for the *tert*-butyl protons and a pair of doublets at δ 6.72 and 7.01 (J = 2.6 Hz) ppm for the aromatic protons, which are in the deshielded region of the bridged double bond. Thus, the methoxy protons appear upfield because of the ring current of the opposite aromatic ring. The structure of the *syn*-conformer is even easily evaluated from the chemical shift of the methoxy protons at δ 3.68 ppm. Here, the *tert*-butyl proton of *syn*-4 is observed at higher field, viz δ 1.11 ppm, due to the shielding effect of the aromatic ring. The aromatic protons of *syn*-4 are reported at much higher field (δ 6.41 and 6.52 ppm) than those of the compound *anti*-4. These data confirm the assigned *anti-* and *syn*-structures for both the conformers of **4**.
<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Single-crystal structures of a) *anti*--[2.4]MCP-1-ene *anti*-4 and b) *syn*--[2.4]MCP-1-ene *syn*-4 (side view and top view). Thermal ellipsoids are drawn at the 50% probability level. All hydrogen atoms are omitted for clarity.</figcaption></figure>
The X-ray structure of *anti*-4 (CCDC 1542177) in Fig. 2 clearly reveals that it is the *anti*-conformer in the solid state and that the two methoxy groups lie on the correlative side of the inner ring, which consists of a long bridging C27–C29 chain pointing outwards to minimize the steric repulsion with the bridge chain. The bond lengths of C30–C29 and C29–C28 in the trimethylene chains and C3–C12 and C16–C13 in the ethylenic chains have standard values at 1.51, 1.53, 1.49 and 1.51 Å, respectively. The length of the double bond in C12–C13 is 1.34 Å, which is similar to that of ethylene. The bond angles defined by C13–C12–C3 and C12–C13–C16 are 121.3(2)° and 121.6(2)°, showing that compound *anti*- [2.4]MCP-1-ene displays a non-distorted conformation. The two benzene rings of [2.4]MCP-1-ene slightly deviate from planarity. The intramolecular distances of C3–C18, C2–C17, C7–C22, C4–C21, C1–C16, C6–C19 are 2.93, 2.83, 9.37, 5.18, 3.20 and 5.14 Å, respectively. | 651 | Sciences naturelles |
cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 4 | The X-ray structure (CCDC 1541642) of syn-4 (Figure 2) clearly demonstrates that 4 exists as the syn-conformer in the solid state and that the two methoxy groups lie on the correlative side of the 18-membered inner ring, which contains the long bridging C27–C30 chain pointing toward the outer direction thereby minimizing steric repulsion with the bridge chain. The selected bond lengths of C6–C30 and C30–C29 in the butamethylene chains and C2–C12 and C14–C17 in the ethylenic chains have typical values at 1.52, 1.53, 1.51 and 1.49 Å, respectively. The length of the double bond in C12–C13 is 1.36 Å, and is similar to that of ethylene. The bond angles defined by C12–C14–C17 and C2–C13–C14 are 118.3(2)° and 119.2(2)°, and reveal that compound 4 displays a non-distorted conformation. The two benzene rings of syn-4 slightly deviate from planarity. The intramolecular distances of C2–C17, C3–C18, C8–C23, C1–C16, C5–C20, C6–C21 are 2.80, 3.53, 5.35, 3.30, 4.69 and 4.05 Å, respectively.
<figure><img src="image_6.png" /><figcaption>**Scheme 3** Synthesis of bis(bromomethyl)-5,15-di-tert-butyl-8,18-dimethoxy-1,2- [2.4]MCP-1-ene 6.</figcaption></figure>
Bromination of 4 with 4.4 equiv. of benzyltrimethylammonium tribromide (BTMA-Br₃)²⁶ in CH₂Cl₂ solution at room temperature for 24 h afforded the corresponding 1,2-bis(bromomethyl)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]-MCP-1-ene 6 in 87% yield (Scheme 3). No bromination product 5 at the alkene bridge (double bond) was observed under the reaction conditions used. This result is quite different from the bromination of the corresponding [2.4]MCP-1-ene which afforded the cis-addition product (to the bridging double bond).²⁵ When 4 was treated with 1.2 equiv. BTMA-Br₃ at room temperature for 24 h, 6 was formed in 30% yield with 70% recovery of 4. In the case of 2.4 equiv. BTMA-Br₃, the yield of 6 increased to 70% yield. These results strongly suggest that the present transformation probably occurred by addition of bromine to the bridged double bond of 4 followed by a two-fold dehydrobromination to give the corresponding 1,2-dimethylene[2.4]MCP 7, from which 1,4-bromine addition occurred to afford 1,2-bis(bromomethyl)[2.4]-MCP-1-ene 6.²⁷⁻³²
The structure of product 6 was proposed on the basis of elemental analyses and spectral data. The mass spectral data for diene 6 (M⁺ = 676, 678 and 680) strongly supports a dibrominated structure. The ¹H NMR spectrum of compound 6 exhibited a singlet peak for the methoxy protons at δ 3.30 ppm as well as the resonances at δ 6.85 and 7.42 ppm (*J* = 2.6 Hz) for the two protons of the aromatic rings. The previously reported¹³b 1,2-bis(bromomethyl)[2.3]MCP-1-ene revealed a lower-field shift of the methoxy protons at δ 3.22 ppm along
with δ 6.99 and 7.19 (*J* = 2.4 Hz) ppm for the two aromatic protons because of the short carbon chain length. The methylene protons of the bromomethyl group were observed as a doublet at δ 4.69 and 4.89 (*J* = 10.3 Hz) ppm. Thus, the introduction of a bromo group on the methyl group at the etheno bridge might restrict the rotation throughout the single bond of C-CH₂Br, which causes the methylene protons diasterotopic environment.
**Scheme 4** Synthesis of 1,2-dibenzo-5,15-di-tert-butyl-8,18-dimethoxy-
<figure><img src="image_7.png" /><figcaption>[2.4]MCP-4',5'-dimethylcarboxylate 9.</figcaption></figure>
To synthesize the diene body from the brominated [2.4]MCP, the reduction of the double bonds does not proceed following the elimination reaction in the presence of a strong basic alcoholic solvent. Interestingly, treatment of 6 with Zn followed by dropwise addition of AcOH in dry CH₂Cl₂ solution at room temperature for 24 h afforded the identical 5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP 7 in 75% yield (Scheme 4). This type of modified reaction has been widely utilized to eliminate the bromine group to form a double bond.
The structure of the diene obtained in the present work was determined from elemental analyses and spectral data. The 300 MHz ¹H NMR spectrum of compound 7 in CDCl₃ revealed a doublet at δ 6.84 and 6.94 ppm for the two protons of the aromatic rings. The *exo*-methylene protons of the ethano-bridge were observed as broad singlets at δ 4.99 and 5.64 ppm, and the protons of the methoxy group were observed at δ 3.23 ppm. The butamethylene bridge protons gave rise to an abstruse signal pattern as predicted for a rigid [2.4]MCP. The protons of the benzylic CH₂ group were observed as two multiplets at δ 2.00–2.07 ppm and 2.70–2.77 ppm, which were additionally split by coupling with the protons of the central CH₂ groups. This central CH₂ groups was also observed as multiplets centered at δ 1.25–1.33 ppm. It was also found these methylene peaks were not merged up to 120 °C in CDBr₃. These findings suggested that the introduction of two double bonds of the ethano-bridge can inhibit the syn-syn conformational flipping of 5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP 7 above this temperature which would exchange H_A and H_B protons | 763 | Sciences naturelles |
cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 5 | of each CH₂ group. These perceptions suggested that the
introduction of two double bonds of the ethano-bridge might
restraint the syn-conformation of 1,2-dimethylene[2.4]MCP 7.
The Diels-Alder reaction of 7 with dimethyl
acetylenedicarboxylate (DMAD) was completed within 12 h
in toluene at reflux. Thus, the Diels-Alder reactivity of
compound 7 exceeds that of 2,3-diphenyl-1,3-butadiene. This
result suggests that the energy of the fixed s-cis conformation
in 7 in the ground and transition state might lower the Diels-
Alder barriers due to the inflexibility of the MCP ring.³³ The
Diels-Alder reaction of 7 with suitable dienophiles followed
by aromatization can be used to prepare a range of areno-
bridged [2.n]MCPs. Compound 7 is conveniently employed
in the reaction with DMAD to provide 8 in good yield. Diels-
Alder adduct 8 was converted to areno-bridged [2.4]MCP 9
by aromatization with dichlorodicyano-p-benzoquinone
(DDQ).
The structure of product **9** was elucidated by spectroscopic methods (¹H NMR and ¹³C NMR), mass spectrometry and elemental analyses. The cyclic dimeric structure was consistent with the mass spectral data for compound **9** (M⁺ = 657). The 300 MHz ¹H NMR spectrum of **9** in CDCl₃ exhibited singlets at δ 3.00 and δ 3.68 ppm for the methoxy protons together with δ 6.92 and 7.05 ppm (*J* = 2.4 Hz) for the two aromatic protons. Based on the spectral data and the chemical conversion, compound **9** is assigned to the structure *anti*-1,2-dibenzo-5,15-di-*tert*-butyl-8,18-di-methoxy[2.4]-MCP-4',5'-dimethylcarboxylate *anti*-9.
<figure><img src="image_8.png" /><figcaption>**Fig. 3.** Drawing of *anti*-1,2-dibenzo-5,15-di-*tert*-butyl-8,18-dimethoxy [2.4]MCP-4',5'-dimethylcarboxylate *anti*-9. Thermal ellipsoids are drawn at the 50% probability level. All hydrogen atoms are omitted for clarity.</figcaption></figure>
In anticipation of future investigations into the ability of
MCPs to be employed as chiral catalysts and ligands, efforts
were made to access the solid-state structures and the high-
resolution NMR spectral data.³⁴ Inherent chirality is a feature
associated with some MCPs and compound *anti*-9 is
predicted to have a plane of chirality. This is because it has
two different types of substituents and bridged linkages which
are fixed in a C₁ symmetrical structure and does not sustain a
conformational change at or near ambient temperature.
Compound *anti*-9 (Figure 3) was crystallized by the slow,
room temperature evaporation of a dichloromethane solution,
and was found to possess the space group *P*-1. Interestingly,
the X-ray analysis disclosed that the areno-bridged [2.4]MCP
*anti*-9 adopts helical chirality (Figure 4), yet surprisingly, the
dihedral angle of the arylenes connected by the phenyl unit is
33.98°.
<figure><img src="image_9.png" /><figcaption>Fig. 4. Schematic diagram of *M*-9 (left side) and *P*-9 (right side).</figcaption></figure>
Therefore, the compound is chiral and the *M*- and *P*-isomers
are packed alternatively in the crystal as depicted
schematically in Figure 5 (CCDC 908369).
<figure><img src="image_10.png" /><figcaption>**Fig. 5.** Packing drawing of *anti*-1,2-dibenzo-5,15-di-*tert*-butyl-8,18-dimethoxy[2.4]MCP-4',5'-dimethylcarboxylate *anti*-9. Thermal ellipsoids are drawn at the 50% probability level. All hydrogen atoms are omitted for clarity.</figcaption></figure>
The chiral properties of the compound *anti*-9 in solution
were investigated by chromatographic resolution using a
chiral column. Interestingly, *anti*-9 exhibits two well resolved
peaks in the ratio 50:50 for the *P*- and *M*-enantiomers. This
finding strongly suggests that the resolution of racemic *anti-9*
could be accomplished by chromatographic separation
using a chiral column. In fact, we have succeeded in resolving
each *P*- and *M*-enantiomer. The circular dichroism (CD)
spectra of the separated enantiomer with precise mirror
images are shown in Figure 6.
From Figure 6, we obtained the symmetrical shape of the
retention time (3.8 min) and the retention time (4.9 min). It
was confirmed that the compound *anti*-9 had no enantiomer. | 575 | Sciences naturelles |
cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 6 | <figure><img src="image_11.png" /><figcaption>**Fig. 6.** (a) Chromatogram of *anti*-1,2-dibenzo-5,15-di-*tert*-butyl-8,18-dimethoxy[2.4]MCP-4',5'-dimethylcarboxylate *anti-9* (HPLC on chiral column). Daicel chiralpak ADeH. Eluent: hexanes. (b) CD spectra of *P*- and *M*-enantiomers of inherently chiral *anti*-1,2-dibenzo-5,15-di-*tert*-butyl-8,18-dimethoxy[2.4]MCP-4',5'-dimethylcarboxylate *anti-9*.</figcaption></figure>
First, one enantiomer which was optically resolved with a chiral column was left in solution (ambient temperature) for 3 weeks, and during this period, no peak for the after-distillate was observed. It was found that compound *anti-9* did not undergo racemization. Only one peak was observed and it turned out that racemization did not occur. Since it was found that racemization did not occur at room temperature, compound *anti-9* was dissolved at 100 °C. It was left for 1 day to investigate whether racemization occurred (SI Figure 21). Since no peak of the after-distillate was observed even after leaving at 100 °C for 1 day, it turned out not to be racemized. The pre-distillate of the *anti-9* was dissolved in CH<sub>2</sub>Cl<sub>2</sub> and the specific rotation measurement was carried out. The specific rotation of compound *anti-9* was [α]<sub>D</sub> = +72 (faster-moving enantiomer on Daicel Chiralpac AD-H with 1 v/v % ethanol in hexane as the eluent) at 240 nm. The specific expected rotation was small because compound *anti-9* had a carbon crosslinking chain length of 4, and so it was a flexible compound.
### 3. Conclusions
In summary, a straightforward and effective method for the synthesis of areno-bridged [2.4]MCP *anti-9* by successive Diels-Alder reactions from 1,2-dimethylene[2.4]MCP 7, together with its chiral conformation is described herein. The conformational behaviour and chirality of [2.4]MCPs were studied both in solution and in the solid state. The racemate of each areno-bridged [2.4]MCP can be readily separated by chiral HPLC to give the enantiomeric pure structure of which absolute configurations have been confirmed by CD spectroscopy. Further mechanistic details of the shorter chain containing [2.n]MCP derivatives are currently being investigated and will be reported on in due course.
### 4. Experimental section
All melting points (Yanagimoto MP-S1) are uncorrected. ¹H and ¹³C NMR spectra (300 MHz) were recorded on a
Nippon Denshi JEOL FT-300 NMR spectrometer in deuteriochloroform with Me₄Si as an internal reference. Mass spectra were obtained on a Nippon Denshi JMS-HX110A Ultrahigh Performance Mass Spectrometer at 75 eV using a direct-inlet system. Elemental analyses were performed by Yanaco MT-5. UV-vis spectra were recorded on a Perkin Elmer Lambda 19 UV/VIS/NIR spectrometer. Here suitable single crystals were selected and mounted on a Bruker APEX 2 CCD diffractometer equipped with graphite-monochromated Mo-Kα radiation. Data were corrected for Lorentz and polarisation effects and for absorption.
#### Materials
Unless otherwise stated, all other reagents used were purchased from commercial sources and were used without further purification. The preparation of 1,4-bis(5-*tert*-butyl-3-formyl-2-methoxyphenyl)butane **1** was described previously.¹⁸
#### 4.1. Synthesis of 1,4-bis(5-*tert*-butyl-3-(1-*hydroxyethyl*)-2-*methoxylphenyl*)butane (2)
To a solution of methylmagnesium bromide [prepared from methyl iodide (14.4 g, 101 mmol) and magnesium (2.05 g, 84.3 mmol)] in Et₂O (45 mL) was added a solution of **1** (8.85 g, 20.9 mmol) in tetrahydrofuran (100 mL) dropwise under the conditions of gentle refluxing. After the reaction mixture was refluxed for an additional 5 h, it was quenched with 10% ammonium chloride (100 mL) and extracted with Et₂O (3 × 100 mL). The extract was washed with water (2 × 100 mL), dried over MgSO₄, and concentrated *in-vacuo*. The residue was recrystallized from hexane to afford 1,4-bis(5-*tert*-butyl-3-(1-*hydroxyethyl*)-2-*methoxyphenyl*)butane **2** (9.35 g, 95%) as colourless prisms. m.p. 110–112 °C. IR: ν<sub>max</sub> (KBr) 3328, 2965, 2857, 2827, 2359, 2344, 1481, 1463, 1363 and 1294 cm⁻¹. δ<sub>H</sub> (CDCl₃) 1.30 (18H, s), 1.53 (6H, d, *J* = 6.4 Hz), 1.67–1.76 (4H, m), 2.36 (2H, s), 2.63–2.73 (4H, m), 3.77 (6H, s), 5.15–5.23 (2H, m), 7.13 (2H, d, *J* = 2.6 Hz) and 7.28 (2H, d, *J* = 2.6 Hz). δ<sub>C</sub> (CDCl₃) 23.89, 29.80, 29.83, 30.84, 30.88, 31.47, 34.45, 61.73, 65.51, 120.75, 126.36, 134.60, 137.32, 146.99 and 153.07. MS (EI): *m/z*: 471 [M⁺]. C₃₀H₄₆O₄ (470.68): Anal. Calcd for C 76.55, H 9.85; Found C 76.23, H 9.90.
#### 4.2. Synthesis of 1,4-bis(3-acetyl-5-*tert*-butyl-2-*methoxylphenyl*)butane (3)
To a solution of C₅H₅NH⁺CrO₃Cl⁻ (31.0 g, 144 mmol) in acetone (300 mL) was added a solution of 1,3-bis(5-*tert*-butyl-3-(1'-hydroxyethyl)-2-methylphenyl)propane **2** (10.62 g, 23.3 mmol) in acetone (100 mL) dropwise at 0 °C. The reaction mixture was stirred at room temperature for 24 h. The reaction mixture was filtered and the filtrate was concentrated *in-vacuo*. The residue was subjected to silica-gel (Wako, C-300; 500 g) column chromatography using as eluent CHCl₃ to afford 1,4-bis(3-acetyl-5-*tert*-butyl-2-*methoxyphenyl*)butane **3** (8.06 g, 74%) as colourless prisms (MeOH). m.p. 112–113 °C. IR: ν<sub>max</sub> (KBr) 2966, 1671, 1572, 1469, 1458, 1222, 1004 and 890 cm⁻¹. δ<sub>H</sub> (CDCl₃) 1.30 (18H, s), 1.71–1.75 (4H, m), 2.64 (6H, s), 2.69–2.71 (4H, m), 3.73 (6H, s), 7.34 (2H, d, *J* = 2.4 Hz) and 7.42 (2H, d, *J* = 2.4 Hz). δ<sub>C</sub> (100 MHz, CDCl₃) 29.72, 30.21, 30.38, 30.81, 31.29, 34.39, 62.73, 124.25, 130.98, 132.91, 135.65, 146.75, 155.13 and 201.82. FABMS: *m/z*: 467.6131 [M⁺]. C₃₀H₄₂O₄ (467.6690): Anal. Calcd for C 77.21, H 9.07; Found C 76.95, H 9.16. | 826 | Sciences naturelles |
cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 7 | ### 4.3. McMurry coupling reaction of (3)
The McMurry reagent was prepared from $TiCl_4$ (13.75 cm³, 125 mmol) and Zn powder (18 g, 275 mmol) in dry THF (500 mL), under nitrogen. A solution of 1,4-bis(3-acetyl-5-tert-butyl-2-methoxylphenyl)butane 3 (3.4 g, 7.5 mmol) and pyridine (22.8 mL, 0.2 mol) in dry THF (250 mL) was added over 60 h to the black mixture of the McMurry reagent by using a high-dilution technique with continuous refluxing and stirring. The reaction mixture was refluxed for an additional 8 h, cooled to room temperature, and hydrolyzed with aqueous 10% $K_2CO_3$ (200 mL) at 0 °C. The reaction mixture was extracted with $CH_2Cl_2$ (3 × 200 mL). The combined extracts were washed with water, dried with $MgSO_4$ and concentrated in-vacuo. The residue was chromatographed over silica gel (Wako C-300, 300 g) with hexane-toluene (1:1) and toluene as eluents to give anti-4 and syn-4 as a colourless solid. Each eluents were recrystallized from hexane to afford anti-4 (1.07 g, 30%) and syn-4 (0.82 g, 21%), respectively.
anti-5,15-Di-tert-butyl-8,18-dimethoxy-1,2-dimethyl[2.4] metacyclophan-1-ene (anti-4) was obtained in 45% yield as colourless prisms (MeOH). m.p. 174–175 °C. IR: $v_{max}$ (KBr) 2966, 1476, 1450, 1229, 1019 and 875 cm⁻¹. $\delta_H$ ($CDCl_3$) 1.10–1.21 (4H, m), 1.32 (18H, s), 1.91–1.99 (2H, m), 2.27 (6H, s), 2.71–2.80 (2H, m), 3.24 (6H, s), 6.72 (2H, d, $J=2.6$ Hz) and 7.01 (2H, d, $J=2.6$ Hz). $\delta_C$ (100 MHz, $CDCl_3$) 21.05, 21.41, 31.58, 31.68, 32.48, 33.91, 59.40, 124.02, 127.15, 129.97, 132.58, 134.48, 143.80 and 153.31. FABMS: *m/z*: 434.6185 [M⁺]. $C_{30}H_{42}O_2$ (434.6533): Anal. Calcd for C 82.90, H 9.74; Found C 82.81, H 9.73.
syn-5,15-Di-tert-butyl-8,18-dimethoxy-1,2-dimethyl[2.4] metacyclophan-1-ene (*syn*-4) was obtained in 21% yield as colourless prisms (hexane). m.p. 174–175 °C. IR: $v_{max}$ (KBr) 2952, 1454, 1472, 1362, 1218, 1015 and 868 cm⁻¹. $\delta_H$ ($CDCl_3$) 0.87–1.00 (4H, m), 1.11 (18H, s), 1.91–2.16 (2H, m), 2.21 (6H, s), 2.68–2.82 (2H, m), 3.68 (6H, s), 6.41 (2H, d, $J=2.3$ Hz) and 6.52 (2H, d, $J=2.3$ Hz). $\delta_C$ (100 MHz, $CDCl_3$) 20.01, 27.81, 31.48, 32.19, 32.38, 33.62, 60.61, 123.59, 124.29, 126.17, 133.26, 133.41, 134.70 and 142.84. FABMS: *m/z*: 434.32 [M⁺]. $C_{30}H_{42}O_2$ (434.65): Anal. Calcd for C 82.90, H 9.74; Found C 82.68, H 9.70.
### 4.4. Bromination of anti-4 with BTMA-Br₃ in CH₂Cl₂
To a solution of *anti-4* (185 mg, 0.44 mmol) in $CH_2Cl_2$ (24 mL) was added BTMA-Br₃ (750 mg, 2.0 mmol, 4.4 equiv.) at room temperature. After the reaction mixture was stirred for 24 h, it was poured into water (20 mL). The organic layer was extracted with $CH_2Cl_2$ (3 × 10 mL). The extract was washed with 10% aqueous sodium thiosulfate (10 mL) and water (10 mL), dried over $MgSO_4$, and concentrated in-vacuo. The residue was column chromatographed over silica gel with hexane and hexane-toluene (1:1) as eluents. Recrystallization of the former eluents from hexane gave *anti-5*,15-di-*tert*-butyl-8,18-dimethoxy-1,2-bis(bromomethyl)[2.4]metacyclophan-1-ene *anti-6* (227 mg, 87%) as colourless prisms (hexane). m.p. 148–149 °C. IR: $v_{max}$ (KBr) 2966, 2900, 2856, 1649, 1553, 1476, 1454, 1354, 1262, 1203, 1170, 1107, 1019, 923, 879, 857, 805, 639, 573 and 529 cm⁻¹. $\delta_H$ ($CDCl_3$) 1.05–1.26 (4H, m), 1.34 (18H, s), 1.93–2.00 (2H, m), 2.69–2.79 (2H, m), 3.30 (6H, s), 4.69 (2H, d, $J=10.3$ Hz), 4.89 (2H, d, $J=10.3$ Hz), 6.85 (2H, d, $J=2.6$ Hz) and 7.42 (2H, d, $J=2.6$ Hz). $\delta_C$ (100 MHz, $CDCl_3$) 21.05, 21.41, 31.58, 31.68, 32.48, 33.91, 59.40, 124.02, 127.15, 129.97, 132.58, 134.48, 143.80 and 153.31. MS (EI): *m/z* found
590, 592, 594 [M⁺]. $C_{30}H_{40}Br_2O_2$ (592.45): Anal. Calcd for C 60.82, H 6.81; Found C 60.91, H 6.73.
### 4.5. Debromination of 6 with zinc powder
To a solution of *anti-6* (100 mg, 0.148 mmol) in $CH_2Cl_2$ (10 mL) and acetic acid was gradually added Zn powder (193 mg, 2.96 mmol) and the system was stirred at room temperature for 24 h. The reaction mixture was filtered and washed with $CH_2Cl_2$ (3 × 10 mL). The filtrate was condensed under the reduced pressure to leave the residue. The residue was column chromatographed over silica gel with $CHCl_3$ as eluent to give a colourless solid. Recrystallization from hexane afforded 5,15-di-*tert*-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]metacyclophane (*anti-7*) (57 mg, 89%) as colourless prisms (hexane). m.p. 148–149 °C. IR: $v_{max}$ (KBr) 2966, 2900, 2856, 1649, 1553, 1476, 1454, 1354, 1262, 1203, 1170, 1107, 1019, 923, 879, 857, 805, 639, 573 and 529 cm⁻¹. $\delta_H$ ($CDCl_3$) 1.25–1.33 (4H, m), 1.31 (18H, s), 2.00–2.07 (2H, m), 2.70–2.77 (2H, m), 3.23 (6H, s), 4.99 (2H, d, $J=2.4$ Hz), 5.64 (2H, d, $J=2.4$ Hz), 6.84 (2H, d, $J=2.6$ Hz) and 6.94 (2H, d, $J=2.6$ Hz). $\delta_C$ (100 MHz, $CDCl_3$) 21.85, 31.55, 31.64, 32.70, 33.43, 33.73, 60.13, 112.50, 126.45, 128.46, 128.66, 131.50, 132.54 and 133.60. FABMS: *m/z*: 432.6028 [M⁺]. $C_{30}H_{40}O_2$ (432.6374): Anal. Calcd for C 83.21, H 9.15; Found C 83.36, H 9.21.
### 4.6. Deals-Alder Reaction of 7 with dimethyl acetylenedicarboxylate
A solution of compound *anti-7* (70 mg, 0.17 mmol) and dimethyl acetylenedicarboxylate (28.5 mg, 0.20 mmol) in toluene (5 mL) was heated at 100 °C for 12 h. After the reaction mixture was cooled to room temperature, the solvent was condensed under the reduced pressure to leave the residue. The residue was column chromatographed over silica gel with toluene-CHCl₃ (1:1) as eluent to give 5,15-di-*tert*-butyl-1,2-(3',6'-dihydrobenzo)-8,18-dimethoxy[2.4]metacyclophane-4',5'-dimethylcarboxylate *anti-8* (95 mg, 97%) as a pale yellow oil. $\delta_H$ ($CDCl_3$) 1.25–1.27 (4H, m), 1.31 (18H, s), 1.90–1.93 (2H, m), 2.66–2.70 (2H, m), 3.26–3.49 (4H, m), 3.24 (6H, s), 3.86 (6H, s), 6.79 (2H, d, $J=2.4$ Hz) and 7.05 (2H, d, $J=2.4$ Hz). MS (EI): *m/z* 574 [M⁺]. $C_{36}H_{46}O_6$ (574.75): Anal. Calcd for C 83.21, H 9.15; Found C 83.36, H 9.21.
### 4.7. Oxidation of 8 with DDQ
A solution of *anti-8* (51.5 mg, 0.092 mmol) and DDQ (27.2 mg, 0.12 mmol) in toluene (5 mL) was heated at 50 °C for 24 h. After the reaction mixture was cooled to room temperature, the solvent was condensed under the reduced pressure to leave the residue. The residue was column chromatographed over silica gel with $CHCl_3$ as eluent to give a colourless solid. Recrystallization from methanol afforded 1,2-dibenzo-5,15-di-*tert*-butyl-8,18-dimethoxy[2.4]metacyclophane-4',5'-dimethylcarboxylate *anti-9* (37.4 mg, 71%) as colourless prisms (MeOH). m.p. 205–207 °C. IR: $v_{max}$ (KBr) 2856, 1730 (C=O), 1477, 1219 and 1019 cm⁻¹. $\delta_H$ ($CDCl_3$) 1.10–1.29 (4H, m), 1.33 (18H, s), 2.01–2.12 (2H, m), 2.75–2.85 (2H, m), 3.00 (6H, s), 3.98 (6H, s), 6.92 (2H, d, $J=2.4$ Hz), 7.05 (2H, d, $J=2.4$ Hz) and 7.90 (2H s). $\delta_C$ (100 MHz, $CDCl_3$) 21.11, 31.54, 32.42, 33.73, 34.10, 52.68, 60.32, 127.26, 129.22, 129.70, 130.09, 131.51, 133.30, 144.18, 145.61, 153.66 and 167.76. EI (MS): *m/z* 572 [M⁺]. $C_{36}H_{44}O_6$ (572.73): Anal. Calcd for C 75.50, H 7.74; Found C 75.71, H 7.69. | 1,090 | Sciences naturelles |
cea-01656007 | Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane | Thamina Akhter; Md. Monarul Islam; Taisuke Matsumoto; Junji Tanaka; Pierre Thuéry; Carl Redshaw; Takehiko Yamato | 2018 | 10.1016/j.tet.2017.11.075 | en | HAL Open Access | Corpus extracted from the HAL open archive, following open access principles, including copyrighted documents (distribution authorized on HAL by the publisher). This must be considered prior to using this dataset for any purpose, other than training deep learning models or data mining. | Chimie | CEA | 8 | ## Acknowledgments
We would like to thank the OTEC at Saga University for financial support. This work was performed under the Cooperative Research Program of "Network Joint Research Center for Materials and Devices (Institute for Materials Chemistry and Engineering, Kyushu University)". CR thanks the EPSRC for a travel award.
## Supplementary data
Electronic Supplementary Information (ESI) available: Details of single-crystal X-ray crystallographic data for compounds *anti-4*, *syn-4* and 9; ¹H, ¹³C NMR for compounds 2–9. For ESI and other electronic format see DOI: 10.1039/x0xx00000x
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