Copper-Catalyzed Trifunctionalization of Alkynes: Rapid Assembly of Oxindoles Bearing Geminal Diboron.

We report a copper catalyzed trifunctionalization of alkynes that provides rapid entry to oxindoles bearing a geminal bis(boronates) side chain, highlighted by the simultaneous formation of one C-C bond and two C-B bonds. This new reaction features simple reaction conditions (ligand free catalysis), a general substrate scope, as well as excellent chemoselectivity. Mechanistic study revealed a reaction sequence in the order of borylation/intramolecular cross coupling/hydroboration, which has been rarely documented.