FACILE TRIPHENYLPHOSPHINE DEOXYGENATION OF BENZOFURAN DIOXETANES, THEIR EPOXIDES AND VALENCE-ISOMERIC QUINONE METHIDES

The triphenylphosphine deoxygenation of 2,3-dimethyllbenzofuran, 2,3-dimethylindole- and 2,3-dimethylindene dioxetanes 2 leads to the respective epoxides 4 through the intermediary phospholanes 3, of which the indene and indole derivatives 3d,e were detected by low-temperature NMR spectroscopy; with excess Ph(3)P the benzofuran dioxetane 2n affords the benzofuran 1a, a novel process in which the resulting benzofuran epoxide 4a is in situ deoxygenated.