Cyanomethylation and Cyclization of Aryl Alkynoates with Acetonitrile under Transition-Metal-Free Conditions: Synthesis of 3-Cyanomethylated Coumarins.

Cyanomethylated coumarins were synthesized via cyanomethylation and cyclization of aryl alkynoates using cheap and available reagent acetonitrile as the cyanomethyl source in the presence of TBPB (tert-butyl peroxybenzoate) under transition-metal-free conditions. For the substrates with various substituents on benzene ring, the reaction proceeded smoothly to give the corresponding products in moderate to good yields. The resulting products could be simply converted into some other related coumarin derivatives.