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Catalytic Asymmetric C sp 3 −H Functionalization under Photoredox Conditions by Radical Translocation and Stereocontrolled Alkene Addition
Author(s) -
Wang Chuanyong,
Harms Klaus,
Meggers Eric
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201607305
Subject(s) - alkene , chemistry , catalysis , rhodium , chiral lewis acid , photochemistry , photoredox catalysis , surface modification , lewis acids and bases , photosensitizer , combinatorial chemistry , organic chemistry , photocatalysis
This work demonstrates how photoredox‐mediated C(sp 3 )−H activation through radical translocation can be combined with asymmetric catalysis. Upon irradiation with visible light, α,β‐unsaturated N‐acylpyrazoles react with N‐alkoxyphthalimides in the presence of a rhodium‐based chiral Lewis acid catalyst and the photosensitizer fac ‐[Ir(ppy) 3 ] to provide a C−C bond‐formation product with high enantioselectivity (up to 97 % ee ) and, where applicable, with some diastereoselectivity (3.0:1 d.r.). Mechanistically, the synthetic strategy exploits a radical translocation (1,5‐hydrogen transfer) from an oxygen‐centered to a carbon‐centered radical with a subsequent stereocontrolled radical alkene addition.