Reactions of γδ-unsaturated ketones with peracids. 2,7-Dioxabicyclo-[2,2,1]heptanes

Abstract

Reaction of a series of γδ-unsaturated ketones with m-chloroperbenzoic acid did not yield the expected epoxides. Depending on the nature of the unsaturated ketone, the reaction products are two (occasionally one) 2,7-dioxabicyclo[2,2,1]heptanes or a mixture of these with two epimeric 6-hydroxy-2,7-dioxabicyclo[2,2,1]heptanes and a 5-hydroxymethyldihydrofuran derivative. Separate treatment of the latter compound with the same oxidant yielded the two 6-hydroxy-dioxabicycloheptanes. A bicyclic orthoacetate, 1,5-dimethyl-3-exo-phenyl-2,7,8-trioxabicyclo[3,2,1]octane, was isolated from the oxidation reaction of 5-methyl-3-phenylhex-5-en-2-one. A common intermediate, in its various stereoisomeric forms, is suggested for the formation of the dioxabicycloheptanes, the dihydrofuran, and the bicyclic orthoacetate. The n.m.r. spectra are discussed in terms of chemical shifts and coupling constants.