Photolysis of diphenyl- and t-butyl(phenyl)-phosphinic azides: dimethyl sulphide as a nitrene trap, and its influence on the Curtius-like rearrangement

Abstract

Photolysis of Ph₂P(O)N₃ in benzene containing MeOH gives a high yield (72%) of the phosphonamidate PhP(O)(OMe)NHPh (3) resulting from Curtius-like rearrangement. When some of the benzene solvent is replaced by Me₂S the yield of the rearrangement product (3) is reduced and the sulphilimine Ph₂P(O)NSMe₂ is formed. At higher concentrations of Me₂S, Ph₂P(O)NHCH₂SMe also becomes an important product. The unsymmetrical azide Bu^tPhP(O)N₃ behaves in a similar way except that low concentrations of Me₂S do not reduce the amount of rearrangement even though some sulphilimine is formed. At higher concentrations of Me₂S rearrangement is partially suppressed but the ratio of the two rearrangement products PhP(O)(OMe)NHBu^t and Bu^tP(O)(OMe)NHPh remains unchanged at 2.05:1.