Unusual photorearrangements of homoconjugated diacylcyclohexa-2,4-dienes

Abstract

The unprecedented triplet sensitized electrocyclic ring opening of various 3a,7a-diacyl-3a,7a-dihydroindans (3)–(5) to the corresponding cyclononatriene derivatives (7)–(11) is reported, direct irradiation at all absorbing wavelengths of the keto-ester (5) resulting in a diastereoselective oxa-di-π-methane (ODPM) rearrangement to the tricyclic product (6); dimethyl 1,2-dimethyl-1,2-dihydrophthalate (15) reacted similarly to give dimethyl E,E,E-2,7-dimethyl-2,4,6-octatrienoate (16), whose structure has been determined by single crystal X-ray diffraction analysis.