Gold-Catalyzed Oxidative Cyclizations of { o-(Alkynyl)phenyl propargyl} Silyl Ether Derivatives Involving 1,2-Enynyl Migration: Synthesis of Functionalized 1 H-Isochromenes and 2 H-Pyrans.

A new and convenient strategy for the synthesis of functionalized 1 H-isochromene and 2 H-pyran derivatives based on gold-catalyzed oxidative cyclizations of o-(alkynyl)phenyl propargyl ether derivatives has been developed. The reaction proceeds via gold-catalyzed highly regioselective oxidation, followed by 1,2-migration of an enynyl group and nucleophlic addition. Isocoumarins were also constructed through oxidative cleavage of the exocyclic double bond of the obtained 1 H-isochromenes.