Photosensitized oxidation of furans. Part 16. Selective formation and chemical properties of 3H-1,2-dioxoles: a new class of cyclic peroxides

Abstract

Direct evidence is provided for the selective formation of the 3H-1,2-dioxoles 1 by thermal conversion of the furan endo-peroxides 2 substituted at C-1 with an alkoxy substituent and at C-5 with an electron-withdrawing group. The thermally unstable dioxoles 1 when heated give, by concerted rearrangements, in addition to the keto esters 3 and 4, the epoxides 5, or 5 and 6. Those like 1c–e, which are disubstituted at C-3, yield the two stereoisomeric epoxides 5c–e and 6c–e, while dioxoles 1a and 1b, which bear a hydrogen atom at C-3, give stereospecifically the epoxides 5a and b. The stereospecificity of the latter reaction is suggested to be due to the preferential conformation 10, which the peroxides 1a,b assume on formation from the related endo-peroxides. Some other chemical properties of the new class of peroxides are reported.