β Elimination of a phosphonate group from an alkoxyl radical - Intramolecular acylation using acylphosphonate derivatives as carbonyl group acceptors

Abstract

The possibility of beta elimination of a phosphonate group in radical reactions was studied. The facile beta elimination of the phosphonate group from an alkoxyl radical was observed for the first time, whereas the beta elimination of the phosphonate group from an aminyl and an alkyl radical did not occur. On the basis of our findings, the use of an acylphosphonate as a carbonyl group radical acceptor was investigated. Radical cyclization of the acylphosphonate in the presence of hexamethylditin in benzene at 300 nm for 2 h gave a cyclopentanone or a cyclohexanone derivative in good yield without the formation of a direct reduction product. The reaction can be carried out in the presence of a catalytic amount of hexamethylditin (0.2 equiv.) under similar conditions. In addition, an alkyl phosphonothiolformate group can act as an alkylthiocarbonyl group equivalent radical acceptor, providing ready access to a thiolactone synthesis.