Photocycloaddition Reactions of Pyrazinopsoralen with Simple Olefins

Abstract

ABSTRACTDirect photolyses of pyrazinopsoralen (PzPs) with excess olefins such as dimethyl fumarate (DMFu), dimethyl maleate (DMMa) and dimethyl ethylidenemalonate (DMEM) gave C4‐photocycloadducts. The photoproducts were determined to be 1:1 C4‐cycloadducts formed through the addition of 4′,5′‐furan double bond of the excited PzPs to the olefins. The fluorescence of PzPs was quenched by olefins with rate constants on the order of 109–1010M‐1/s. The appearance of the long‐lived fluorescence component implies a singlet exciplex mechanism for the photocycloaddition reaction of PzPs with excess olefins.