Palladium-Catalyzed [3+3] Annulation between Diarylamines and ,-Unsaturated Acids through CH Activation: Direct Access to 4-Substituted 2-Quinolinones

A C-H activation strategy has been successfully employed for the high-yielding synthesis of a diverse array of 4-substituted 2-quinolinone species by a palladium-catalyzed dehydrogenative coupling involving diarylamines. This intermolecular annulation approach incorporates readily available alpha,beta-unsaturated carboxylic acids as the coupling partner by suppressing the facile decarboxylation. Based on preliminary mechanistic studies, a reaction sequence is proposed, involving ortho palladation, pi-coordination, beta-migratory insertion, and beta-hydride elimination.