Enantioenriched Methylene-Bridged Benzazocanes Synthesis by Organocatalytic and Superacid Activations |
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Authors: | Dr Rodolphe Beaud Dr Bastien Michelet Yasmin Reviriot Dr Agnès Martin-Mingot Prof Jean Rodriguez Dr Damien Bonne Prof Sébastien Thibaudeau |
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Institution: | 1. Aix Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille, France;2. Université de Poitiers, UMR-CNRS 7285, IC2MP, Equipe Synthèse Organique “Superacid Group”, 4 rue Michel Brunet, TSA 51106, 86073 Poitiers Cedex 9, France |
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Abstract: | Achieving in a straightforward way the synthesis of enantioenriched elaborated three-dimensional molecules related to bioactive natural products remains a long-standing quest in organic synthesis. Enantioselective organocatalysis potentially offers a unique opportunity to solve this problem, especially when combined with complementary modes of activation. Here, we report the sequential association of organocatalytic and superacid activations of simple linear achiral readily available precursors to promote the formation of unique highly elaborated chiral methylene-bridged benzazocanes exhibiting three to five fully-controlled stereocenters. This peculiar backbone, difficult to assemble by standard synthetic approaches, is closely related to bioactive natural and synthetic morphinans and benzomorphans. The formation of a highly reactive chiral 7-membered ring N-acyl iminium superelectrophilic ion, evidenced by low-temperature in situ NMR experiments, triggers a challenging stereoselective Friedel–Crafts-type cyclization. |
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Keywords: | Acyliminium-Ion Benzazocan Organokatalyse Pictet-Spengler-Reaktion Superelektrophile |
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