Electrocyclic reactions. Part VII. Irradiation of 3,5-dibromo-2,6-di-methylhepta-2,5-dien-4-one (αα′-dibromophorone)

Abstract

Irradiation of 3,5-dibromo-2,6-dimethylhepta-2,5-dien-4-one in hexane under nitrogen at ca. 300 nm yields, as the major product, 2-bromo-5-isopropylidene-3-methylcyclopent-2-enone. The minor product is a symmetrical photodimer, (C₉H₁₀O)₂, of tricyclo[5.3.0.0^2,6]decane type, produced by a [_π2_s+_π2_s] process; it is susceptible to autoxidation in air.