Alkyne Carbonylation by Radicals: Tin-Radical-Catalyzed Synthesis of -Methylene Amides from 1-Alkynes, Carbon Monoxide, and Amines

摘要

Radical reactions have become an important tool in organic synthesis.[1] Radical carbonylation is a useful method for the preparation of a variety of carbonyl compounds.[2] We previously reported that acyl-radical cyclization onto an imine nitrogen atom provides a useful route to lactam rings.[3] We also recently found that intramolecular trapping of an -ketenyl radical by an amino group leads to the formation of cyclic amides.[4] Acrylamides and derivatives thereof are employed in a wide range of organic reactions, which include nucleophilic additions, cycloaddition reactions, and radical reactions, to name just a few.[5] They are also extensively used in the synthesis of polymeric materials.[6] The goal of this work was to develop a novel synthesis of acrylamide derivatives by taking advantage of a hybrid radical/ionic reaction involving the radical carbonylation of alkynes and subsequent ionic trapping of the resulting carbonyl-containing radical species by amines (Scheme 1).[7], [8]