Photocyclization of a naphthyl substituted Y-enyne

Y-enyne 1 undergoes electrocyclic ring closure, via a cumulene intermediate 2. to photoproduct 3 upon irradiation at 350 run in the presence/absence of air. In non-polar solvents, a [1,5] H-shift affords the photoproduct. In MeOX (X=H/D), protonation/deuteration of the central allenic carbon in 2 occurs. The X-ray Structure of 3, the photoproduct upon irradiation of 1 in benzene. is reported. (C) 2002 Elsevier Science Ltd. All rights reserved.