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1-(2-Nitrophenyl)-1-phenylamine and methyl 4-((2-nitrophenyl)amino)benzoate have been transformed into their corresponding urea derivatives through the action of chlorosulfonyl isocyanate. The initial sulfimidate product from the former reaction has sufficient stability so that it can be isolated and characterized as its disodium salt, and this, as well as three other subsequent products, have been characterized by X-ray diffraction. The corresponding intermediary urea was converted into its hydrazine derivative via a Hofmann rearrangement under oxidative conditions. Density functional theory has been used to examine the nature of the intermediates and transition states for the Hofmann rearrangement. There is little theoretical indication for a cyclic aziridinonium intermediate and the transition state between the urea and the isocyanate corresponds to a reactant-like rotation of the planar singlet nitrene before migration and formation of the new N-N bond. Key words: hydrazines, Hofmann rearrangement, sulfimate salt. La 1-(2-nitrophenyle)-1-phenylamine et la 4-((2-nitrophenyle)amino)benzoate de methyle ont ete transforme par leur reaction avec l'isocyanate de chlorosulfonyle en leurs urees correspondantes. Dans le premier cas, le produit initial de cette reaction, un sulfimide, demontre une stabilite qui permet son isolement comme sel de sodium. Celui-ci ainsi que trois produits ulterieurs ont ete caracterises par diffraction de rayons X. L'uree de 1-(2-nitrophenyle)-1-phenylamine a ete transforme en hydrazine par rearrangement de Hofmann sous conditions oxydatives. La theorie de la fonctionnelle de la densite a ete utilise afin d'examiner les intermediates et les etats de transition de ce rearrangement. Les calculs indiquent qu'un intermediate aziridononium cyclique est peu probable et que l'etat de transition qui mene de l'uree a l'isocyanate et finalement a l'hydrazine correspond a une rotation de la nitrene planaire de forme singulet avant sa migration et la formation d'une nouvelle liaison entre les deux atomes d'azote. Mots-cles: hydrazines, Hofmann rearrangement, sel sulfimate., Introduction Although 1,1-diarylhydrazines have proven useful in medicinal chemistry (1) and in the catalysis of hydrohydrazination reactions, (2, 3) their syntheses (4) often require a two-step nitrosation/reduction of a diaryl [...]