Direct C-3 alkylation of coumarins decarboxylative coupling with carboxylic acids

A new method for selective C-3 alkylation of coumarins using carboxylic acids as alkyl sources is reported. This process offers a practical method for the facile construction of 3-alkyl coumarins with a broad substrate scope. The reaction works under metal-free and aqueous media and both cyclic and acyclic aliphatic carboxylic acids participate in this radical C-C cross coupling reaction. A metal-free direct alkylation of coumarins using carboxylic acids in aqueous media with a broad substrate scope is devised.