Photoredox Catalytic Synthesis of Indoles via Direct N-H Activation to Generate Putative Aminyl Radicals
Juulia Talvitie1, Andrés Mollar-Cuni1, Jarkko Nyman1
1Department of Chemistry, University of Helsinki, 00014 Helsinki, Finland.
Abstract:
Visible-light-excited 3,6-bis(trifluoromethyl)-9,10-phenanthrenequinone (PQ-CF3*) was used as a photocatalyst in the synthesis of 3-substituted N-pyridyl indoles via cyclization of 2-vinylarylamines, where the photocatalyst was catalytically regenerated with the chloro(pyridine)cobaloxime complex. The versatility of the reaction was shown with 22 substrates providing up to 83% yields. Based on the mechanistic studies, we propose that PQ-CF3 directly activates the N-H bond, generating a nitrogen-centered aminyl radical as the key intermediate.
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