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 prese nce of diethyl phosphite or diphenylphosphine oxide has been investigated. These reactions involve addition of the trichloromethyl radical to the dien e followed by a 5-exo-trig cyclisation reaction. The resultant cyclic prima ry radical can abstract a chlorine atom from CCl4 or alternatively, abstrac t a hydrogen atom from the solvent or the organophosphorus compound. (C) 20 01 Elsevier Science Ltd. All rights reserved.