Aminations with O-Diphenylphosphinylhydroxylamine A Critical Evaluation

A critical evaluation is presented of the scope of amination reactions with O-diphenylphosphinylhydroxylamine (O D PH ) as compared to those using hydroxylamine-O-sulfonic acid (H O SA ). Aminations with O D PH of isopropyl, r-butyl and cyclohexyl carbanions derived from the corresponding Grignard reagents, gave the corresponding amines in 36, 34 and 50 percent yields, respectively. The amination with H O SA of the same carbanions under similar conditions was unsuccessful. The aminative quarternization of the tertiary nitrogen of pyridine andquinoline with ODPH proceeded with comparable yields to those obtained with H O SA. An improved one flask amination with O DPH of indole, skatole and carbazole was achieved in 52—62 percent yields. The amination under the same conditions using H O SA gave consistently lower yields. Several other amination reactions which have been reported for HOSA were unsuccessful using O DPH. The conclusion is reached that overall the O DPH reagent is much less versatile than H OSA. Nevertheless, in the aminations of NH groups of heterocyclic compounds ODPH appears to be superior to H O SA and is the reagent of choice, in particular, since the preparation of ODPH is much less harzardous than that of H O SA.