The photochemistry of 2-vinyldiphenylacetylene and related compounds

Abstract

Irradiation of solutions of 2-vinyldiphenylacetylene (5) under anaerobic conditions gives 2-phenylnaphthalene (9) in 90% yield. Several derivatives of (5) behave similarly. The reaction is ascribed to the primary formation of a cyclic allene (29), as has been proposed previously for the analogous photocyclization of 1,4-diarylbutenynes into phenylaromatic compounds. The end-product arises from (29) either via a 1,5-hydrogen shift or by addition and elimination of a proton. Irradiation of 2-ethynylstilbene (21) also yields (9), but 1-ethynylphenanthrene (22) is formed as a side-product.