RING-CLOSURE REACTIONS OF ALKENYL OXIMES INDUCED BY PERSULFATE ANION OXIDATION OF DIPHENYL DISELENIDE - FORMATION OF 1,2-OXAZINES AND CYCLIC NITRONES

A strongly electrophilic phenylselenenylating agent is produced from the reaction of diphenyl diselenide with ammonium persulfate, in the presence of trifluoromethanesulfonic acid, in acetonitrile or nitromethane, at room temperature. This reagent induces regioselective ring-closure reactions on gamma-alkenyl oximes to afford (phenylseleno)methyl-substituted 1,2-oxazines and/or cyclic nitrones, indicating that, depending on its geometry, the oxime group can act either as an oxygen or as a nitrogen nucleophile. However, the ratio of the two heterocyclic reaction products does not reflect the Z/E ratio of the starting oximes, the formation of the five-membered cyclic nitrone being largely preferred over the six-membered 1,2-oxazine. Several derivatives which confirm the proposed structures and at the same time exemplify the synthetic utility of the products obtained with this reaction have also been prepared.