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Repairing the thiol-ene coupling reaction

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2014
Author Povie Guillaume, Tran Anh Tuan, Bonnaffé David, Habegger Jacqueline, Hu Zhaoyu, Le Narvor Christine, Renaud Philippe,
Project Synthetic Methods for total Synthesis of Natural Products
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Original article (peer-reviewed)

Journal Angewandte Chemie - International Edition
Volume (Issue) 53(15)
Page(s) 3894 - 3898
Title of proceedings Angewandte Chemie - International Edition
DOI 10.1002/anie.201309984

Abstract

Thiol-ene coupling (TEC) reactions emerged as one of the most useful processes for coupling different molecular units under reaction mild conditions. However, TEC reactions involving weak C-H bonds (allylic and benzylic fragments) are difficult to run and often low yielding. Mechanistic studies demonstrate that hydrogen-atom transfer processes at allylic and benzylic positions are responsible for the lack of efficiency of the radical-chain process. These competing reactions cannot be prevented, but reported herein is a method to repair the chain process by running the reaction in the presence of triethylborane and catechol. Under these reaction conditions, a unique repair mechanism leads to an efficient chain reaction, which is demonstrated with a broad range of anomeric O-allyl sugar derivatives including mono-, di-, and tetrasaccharides bearing various functionalities and protecting groups. In good repair: Undesired hydrogen-atom transfers are responsible for the lack of efficiency in thiol-ene coupling reactions involving allyl glycosides. This competing reaction cannot be prevented but can be very efficiently repaired by carrying out the reaction in the presence of triethylborane and catechol. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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