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Enantioselective Organo‐Photocatalysis Mediated by Atropisomeric Thiourea Derivatives
Author(s) -
Vallavoju Nandini,
Selvakumar Sermadurai,
Jockusch Steffen,
Sibi Mukund P.,
Sivaguru Jayaraman
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201310940
Subject(s) - photocatalysis , enantioselective synthesis , thiourea , chemistry , photochemistry , catalysis , hydrogen bond , organocatalysis , excited state , combinatorial chemistry , organic chemistry , molecule , physics , nuclear physics
Can photocatalysis be performed without electron or energy transfer? To address this, organo‐photocatalysts that are based on atropisomeric thioureas and display lower excited‐state energies than the reactive substrates have been developed. These photocatalysts were found to be efficient in promoting the [2+2] photocycloaddition of 4‐alkenyl‐substituted coumarins, which led to the corresponding products with high enantioselectivity (77–96 % ee ) at low catalyst loading (1–10 mol %). The photocatalytic cycle proceeds by energy sharing via the formation of both static and dynamic complexes (exciplex formation), which is aided by hydrogen bonding.