Direct Synthesis of Coumarin Derivatives from Alkynoic Esters via Dual Organocatalysis

Abstract An efficient synthetic method for coumarin derivatives was developed using a dual organocatalytic reaction. A combination of p-toluenesulfonic acid monohydrate and piperidine was found to efficiently catalyze the cyclization between salicylaldehydes and alkynoic esters to give various coumarin derivatives in good yield and high selectivity. Mechanistic and kinetic data suggested that the conjugate addition between piperidine and alkynoic esters played a crucial role in the reaction mechanism.