Photosensitized oxidation of furans. Part 15. Limitations to the formation of carbonyl oxides from 2-alkoxyfurans, and direct evidence for the first 3H-1,2-dioxole

Abstract

Formation of the carbonyl oxides 3, via the furan endo-peroxides 1, can be accomplished only by dye-sensitized photo-oxygenation of 2-alkoxyfurans 2 unsubstituted at C-4, electron-withdrawing substituents at C-3 making the formation selective. Hydrogen or phenyl substituents at C-3 give rise either to carbonyl oxides 3 or to 3H-1,2-dioxoles 8, the predominance of one over the other being dependent on the polarity of the solvent. For the first time, direct evidence for the formation of a 3H-1,2-dioxole, 8e. has been obtained.