Photodimerization of Arenediynes

Significance

Cyclic enediynes as well as terminal acyclic enediynes are well known to undergo photochemical C^¹-C⁶ cycloaromatization. The authors explored the reactivity of naphthalenyl-substituted arenediynes (1 and 2). While the methoxy-substituted derivative 2 undergoes a photo-­Bergman cyclization upon irradiation at 300 nm, 1 shows no formation of C^¹-C⁶ or C^¹-C⁵ under these conditions. Irradiation of 1 at 350 nm, however, yields a photodimerized product (4).