Radical cyclisation reactions involving phosphonyl radicals: the use of phosphites and phosphine oxides as alternatives to tributyltin hydride

Free radical cyclisation of a variety of 1,6-dienes using CCl4 in the presence of diethyl phosphite or diphenylphosphine oxide has been investigated. These reactions involve addition of the trichloromethyl radical to the diene followed by a 5-exo-trig cyclisation reaction. The resultant cyclic primary radical can abstract a chlorine atom from CCl4 or alternatively, abstract a hydrogen atom from the solvent or the organophosphorus compound.