Base induced rearrangement reactions of N-phosphinoyl-O-sulfonylhydroxylamines. Observation of a phosphonamidic–sulfonic anhydride intermediate by NMR spectroscopy¹

The hydroxylamine derivative PhRP(O)NHOSO₂Me (R = PhMeCH) reacts with Bu^tNH₂ to give the rearrangement product RP(O)(NHPh)NHBu^t by way of a reactive but non-transient intermediate. At low amine concentrations the intermediate can be observed by ³¹P NMR spectroscopy; it is thought to be the mixed anhydride RP(O)(NHPh)OSO₂Me as it has the same chemical shift as an authentic sample generated from RP(O)(NHPh)Cl and AgOSO₂Me. The intermediate is formed with high (or complete) stereospecificity but it reacts with Bu^tNH₂ with low stereospecificity.