Light‐Driven Vitamin B₁₂‐Catalysed Generation of Acyl Radicals from 2‐S‐Pyridyl Thioesters

Acyl radicals are invaluable intermediates in organic synthesis, however their generation remains challenging. Herein, we present an unprecedented light‐driven, cobalt‐catalysed method for the generation of acyl radicals from readily available 2‐ S ‐pyridyl thioesters. The synthetic potential of this methodology was demonstrated in the Giese‐type acylation of activated olefins in the presence of heptamethyl cobyrrinate. This vitamin B 12 derivative proved to be the most efficient catalyst in the studied process. The developed method features broad substrate scope (38 examples), good functional group tolerance, and mild reaction conditions. Moreover, it is easily scalable (illustrated on a 20‐fold scale‐up procedure), enabling its preparative use. Mechanistic studies revealed that the reaction proceeds via a radical pathway with the key steps involving the formation of an acyl‐vitamin B 12 complex and subsequent photolysis of the Co−C bond. magnified image