Dimethylphosphoramidous dichloride (N,N-dimethylamidodichlorophosphite) may be used in the synthesis of the following N,N-dimethylamidotetrachlorophosphorane, O-propylchloroformimino-N,N-dimethylamidochlorophosphate, bisarylsulphonyldiazadiphosphetidines.