Photosensitized oxidation of furans. Part 7. Solvent effects in thermal conversion of the endo-peroxides of arylfurans

Abstract

Thermal conversion of the endo-peroxides of the arylfurans (1) in a polar aprotic solvent leads to aroylenol esters (4) and diaroyl epoxides (3), the predominance of one over the other being concentration dependent. The results can be rationalized on the basis of the intermediacy of dipolar species, e.g.(6a) and/or (7a–d), which are formed in the first stages of the reaction and can react intra- and/or inter-molecularly. The behaviour of the peroxides (1) in an apolar solvent suggests that in this case the epoxides (3) are predominantly formed by a different route, probably involving an intramolecular synchronous rearrangement.