Photoconversion of 2,6-bis(alkylthio)-3,5-diphenyl-4H-thiopyran-4-ones into 3,4-bis(alkylthio)-2,5-diphenylcyclopentadienones
Abstract
The irradiation of 2,6-bis(alkylthio)-3,5-diphenyl-4H-thiopyran-4-ones (2) with a medium-pressure mercury arc lamp through a Pyrex filter produced 3,4-bis(alkylthio)-2,5-diphenylcyclopentadienones. The quantum efficiency for formation of cyclopentadienone derivatives was very low (Φ= 0·0002). Sensitization and quenching studies indicate that the reaction involves the triplet state of compounds (2). Cycloadditions of the photoproduct with some dienophiles were studied. The mechanism of the photochemical rearrangement of compounds (2) is discussed.