Visible-light-induced N-heterocyclic carbene mediated cascade transformation of N-alkenoxypyridinium salts

While N-alkenoxypyridinium salts are widely used for the synthesis of alpha-functionalized ketones via umpolung strategy, such approaches are usually limited to special nucleophiles at high temperatures. Herein, we developed an alternative photoinduced N-heterocyclic carbene (NHC)- mediated functionalization of N-alkenoxypyridinium salts with various nucleophiles, including tetramethylammonium azide, secondary amines, aryl and alkyl thiols, and even the challenging C(sp(3))-nucleophiles, under mild conditions. A cascade radical-radical coupling/nucleophilic substitution sequence was proposed, wherein the NHC enabled the formation of a photoactive electron donor-acceptor complex for alpha-iodo ketone synthesis. (C) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.