Photochemical reaction of 1-(o-methylaryl)-2,2-dimethyl 1,3-diketones in the presence of oxygen

Abstract

Irradiation of 1-(o-methylaryl)-2,2-dimethyl 1,3-diketones 1a–c having an isopropyl group on C-3 in the presence of oxygen gave the peroxides 7a–c and the lactones 8a–c, whereas irradiation of 1-(o-methylaryl)-2,2-dimethyl 1,3-diketones 1d–g having a methyl or ethyl group on C-3 gave 1,4-epoxy- and 1,4-epidioxy-3-benzooxepin-1-ols 9d–g and 10d–g, along with the peroxide 7d,g and the lactone 8d–g.