Palladium-catalyzed direct oxidative Heck-Cassar-Sonogashira type alkynylation of indoles with alkynes under oxygen

A novel Pd(II) catalyzed direct oxidative Heck-Cassar-Sonogashira type alkynylation of indoles with terminal alkynes under an atmosphere of O(2) is developed. Unlike previous methods, the reaction does not require the pregeneration of indolyl halide or alkynyl halide. Furthermore, only a catalytic amount of base is required and oxygen was used as the ultimate green'' terminal oxidant.