Palladium-catalyzed oxidative ethoxycarbonylation of aromatic C-H bond with diethyl azodicarboxylate

This communication describes the Pd(OAc)2-catalyzed ethoxycarbonylation reactions of aromatic C-H bonds using diethyl azodicarboxylate (DEAD) together with Oxone or K2S2O8. Substrates such as 2-arylpyridines, pyrrolidinone, acetylindoline, quinoline, and oximes were ethoxycarbonylated with excellent chemo- and regioselectivities. The catalytic reaction is probably initiated by chelation-assisted cyclopalladation of the ortho-C-H bond. Preliminary studies suggested that reactive ethoxyacyl radicals generated from thermal decomposition of DEAD were involved in the ester formation.