Radical Cyclizations of Alkenyl Acylphosphonate Derivatives under Thermal and Photochemical Conditions.

Abstract

Organo-phosphorus compounds S 0080Radical Cyclizations of Alkenyl Acylphosphonate Derivatives under Thermal and Photochemical Conditions. -Cyclizations of alkenyl acylphosphonates (I), (III), and (VII) in the presence of a combination of benzoyl peroxide and diethyl phosphite occur smoothly under thermal conditions. The generated phosphonyl radical not only works as a radical carrier but also adds to the alkenyl moiety of the acylphosphonate. Similar results are obtained by photochemically induced cyclizations of alkenyl acyldiphenylphosphine oxides (IX), (XIII), and (XV). However, the intramolecular cyclization of butenyl phosphino thiolformate (XIII) yields the thiolactone (XIV), whereas the higher homologues of (XIII), (XI), afford the tetrahydrothiophene derivatives (XII), due to an intramolecular homolytic substitution at sulfur. -(CHO, C. H.; KIM*, S.; YAMANE, M.; MIYAUCHI, H.; NARASAKA, K.; Bull. Chem.