Radical cyclizations of alkenyl acylphosphonate derivatives under thermal and photochemical conditions

Abstract

The use of alkenyl acylphosphonate and acylphosphine oxide derivatives as acceptors in radical cyclizations was studied under thermal and photochemical conditions, respectively. The cyclizations of alkenyl acylphosphonates under thermal conditions occurred smoothly in refluxing dioxane using benzoyl peroxide as an initiator; the addition of diethyl phosphite increased the chemical yield. Photochemically induced cyclizations of alkenyl acyldiphenylphosphine oxides at 300 nm gave similar results, although a notable difference was observed in one case. The intramolecular cyclization of S-but-3-enyl phosphinothiolformates occurred under thermal and photochemical conditions, providing thiolactones, whereas S-pent-4-enyl phosphinothiolformate afforded the tetrahydrothiophene derivative under similar conditions.