Organocatalyzed Step‐Growth Polymerization through Desymmetrization of Cyclic Anhydrides: Synthesis of Chiral Polyesters |
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Authors: | Dr Anthony Martin Dr Frédéric Robert Prof?Dr Daniel Taton Prof?Dr Henri Cramail Dr Jean‐Marc Vincent Prof?Dr Yannick Landais |
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Institution: | 1. Université de Bordeaux, Institut des Sciences Moléculaires (ISM), UMR‐CNRS 5255, 351, Cours de la Libération, 33405 Talence Cedex (France);2. Université de Bordeaux, Laboratoire des Polymères Organiques (LCPO), UMR‐CNRS 5629, 33600 Pessac (France) |
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Abstract: | The polymerization of prochiral bis‐anhydrides with diols catalyzed by a cinchona alkaloid was shown to provide chiral polyesters in good yields and with high levels of stereocontrol. The structures of the polyesters were determined by 1H and 13C NMR analyses, whereas their size was estimated by both size‐exclusion chromatography (SEC) and MALDI‐TOF mass spectrometry, which indicated that moderate degrees of polymerization were attained through this step‐growth polymerization. The enantioselectivity of the process was evaluated by using chiral HPLC analysis of the bis‐lactones resulting from a controlled chemoselective degradation of the polyesters. The best stereocontrol was reached for oligomers formed from bis‐anhydride and diol monomers bearing rigid aromatic spacers between the reactive functional groups. In this case, average enantioselectivities were comparable to those observed during ring‐opening of simple anhydrides with similar alcohols. In contrast, the use of more flexible spacers between reactive entities generally led to lower levels of stereocontrol. |
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Keywords: | anhydrides desymmetrization enantioselectivity organocatalysis polyesters polymerization |
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