Palladium(II)/Polyoxometalate-Catalyzed Direct C-3 Alkenylation of Indoles using Dioxygen as the Terminal Oxidant

An efficient and practical synthetic method has been developed for the preparation of 3-vinylindoles by the direct CH olefination of indoles with alkenes. The transformation is catalyzed by palladium acetate combined with 12-molybdophosphoric acid and uses oxygen as the terminal oxidant. 4-Dimethylaminopyridine (DMAP) was observed to be an effective additive for the olefination reaction. Functional groups such as methoxy, benzyloxy, fluoro, bromo, ester, phenyl, and methyl were tolerated under the reaction conditions.