Palladium-Catalyzed Intermolecular Dehydrogenative C-2 Pentenylation of Indoles with 2-Methyl-2-butene.

Five-carbon (C 5 ) units are the fundamental building blocks that constitute a multitude of natural products. Herein we report an unprecedented unusual C 5 functionalization of indole regioselectively at the C-2-position enabled by a (2-pyridyl)sulfonyl-directing palladium-catalyzed dehydrogenative strategy with a bulk chemical 2-methyl-2-butene as a C 5 source. Compared to typical C 5 functionalization using pentenyl alcohols, carbonates, borates, or halides as the C 5 source, the protocol not only has a low cost advantage but also is of atom and step economy.