Photochemical reactions of acetone with 2,3-dimethylbut-2-ene

Abstract

U.v. irradiation of acetone in the presence of 2,3-dimethylbut-2-ene (1) leads to the formation in reasonable quantum yields of seven primary photoproducts: two unsaturated ethers [(2) and (3)], an oxetan (4), two unsaturated alcohols [(5) and (6)], and two hydrocarbons [(7) and (8)]. Prolonged irradiation yields a secondary photoproduct, the oxetan (9). Irradiation of hexadeuterioacetone and (1) gives the deuteriated 1 : 1 adducts (2a)–(6a). The unsaturated ethers (2) and (3) and the oxetan (4) appear to arise from a 1,4-diradical intermediate (15) by competing hydrogen transfers and ring closure, respectively. The results of quenching experiments suggest that both singlet and triplet excited states of acetone are involved in the formation of the adducts (2)–(6).