N-(alkylphenylphosphinoyl)hydroxylamines: highly selective migration of the phenyl group in the base-induced rearrangement of their O-methylsulphonyl derivatives

Abstract

The N-(alkylphenylphosphinoyl)hydroxylamines RPh(O)NHOH (R = Me, Et, or Prⁱ) have been prepared and converted into their O-methylsulphonyl derivatives RPhP(O)NHOMs. These readily rearrange on treatment with methylamine, t-butylamine, or sodium methoxide–methanol to give only the products RP(O)(NHPh)X (X = NHMe, NHBu^t, or OMe) resulting from migration of the phenyl group. The rates of reaction are essentially the same when R = Me and R = Prⁱ, indicating that rearrangement is not brought about by nucleophilic attack at phosphorus. A likely mechanism involves base-induced rearrangement to a monomeric metaphosphonimidate which then reacts rapidly with the nucleophile.