Divergent Reactivity in Palladium-Catalyzed Annulation with Diarylamines and ,-Unsaturated Acids: Direct Access to Substituted 2-Quinolinones and Indoles

A palladium-catalyzed CH activation strategy has been successfully employed for exclusive synthesis of a variety of 3-substituted indoles. A [3+3] annulation for synthesizing substituted 2-quinolinones was recently developed by reaction of ,-unsaturated carboxylic acids with diarylamines under acidic conditions. In the present work, an analogous [3+2] annulation is achieved from the same set of starting materials under basic conditions to generate 1,3-disubstituted indoles exclusively. Mechanistic studies revealed an ortho-palladation--coordination--migratory insertion--hydride elimination reaction sequence to be operative under the reaction conditions.