Dihydrobiphenylenes through Ruthenium-Catalyzed 2+2+2 Cycloadditions of of ortho-Alkenylarylacetylenes with Alkynes

摘要

A new synthetic route to dihydrobiphenylenes has been developed. The process involves a mild Ru~(II)-catalyzed 2+2+2 dimerization of ortho-alkenylarylacetylenes or its more versatile variant, the Ru-catalyzed 2+2+2 cycloaddi-tion of ortho-ethynylstyrenes with alkynes. Mechanistic aspects of this 2+2+2 cycloaddition are discussed.