Oxidation of 2,7-dioxabicyclo[2,2,1]heptanes with m-chloroperbenzoic acid. 2,7,8-Trioxabicyclo[3,2,1]octanes

Abstract

Oxidation of several 1,4-dimethyl-6-phenyl-2,7-dioxabicyclo[2,2,1]heptanes with m-chloroperbenzoic acid yielded the title bicyclic orthoesters, with conservation of configuration of the 6-substituents. With 6-endo-alkyl-6-exo-phenyl substituents, the oxidation was directed towards the 1-methyl, yielding the 1-hydroxymethyl analogue of the starting material. A perester, resulting from the addition of a peracid molecule to the bicyclic acetal, is suggested as an intermediate in these reactions. A conformational analysis, based on n.m.r. spectra, indicates a boat conformation for the six-membered ring of the orthesters bearing a 3-endo-phenyl substituent.