Aromatic and aliphatic N, O-divinylhydroxylamine systems generated in situ from hydroxylamine derivatives smoothly undergo [3, 3] rearrangement. The base-catalyzed formation and rearrangement of enolates or dienolates of N-aryl-O-acylhydroxylamines, N, 0- diacylhydroxylamines and N-acylhydroxylamine-0-carbamates result in C—C or C—N bond formation with cleavage of the N* O bond. The usefulness of [3, 3] sigmatropic ...