The reactivity of organophosphorus compounds. Part 35. Pyrolysis of 3-aryl- and 3-alkyl-2,3-dihydro-1,3,2-benzoxazaphosph(V)oles

Abstract

Pyrolysis of 2,2-diphenyl-2-methoxy derivatives of the title compounds in the gas phase gives phosphinates or phosphinamidates derived from the substrate by formal loss of methylene. Control experiments show that the reaction involves radical cleavage initiated by rupture of the oxazaphosph(V)ole ring. Pyrolysis of 3-aryl-2,2-dimethoxy-2-phenyl derivatives of the title compounds under similar conditions results in the formation of 3-aryl-2,3-dihydro-2-oxo-2-phenyl-1,3,2-benzoxazaphospholes. No significant products could be isolated from 2,2,2-trimethoxy derivatives, though vigorous conditions were required for their complete breakdown. The pyrolysis of the corresponding 2,2-diphenyl-2-ethoxy, 2,2-diethoxy-2-phenyl, and 2,2,2-triethoxy compounds gave higher yields of similar products, possibly via a six-centre concerted elimination.