Bimolecular Oxidative C–H Alkynylation of α-Substituted Isochromans

A bimolecular oxidative C–H functionalization of secondary benzylic ethers for new C–C bond formation has been established. A wide range of α-substituted isochromans underwent oxidative C–H alkynylation with diverse potassium trifluoroborates, affording respective oxygen-heterocycles bearing α-tetrasubstituted stereocenters in high efficiency.