Reaction of Spiro[4H-3, 1-benzoxazine-4, 4'-piperidin]-2(1H)-one Derivatives and Related Compounds with Phosphorus Oxychloride

Abstract

Treatment of spiro[4H-3, 1-benzoxazine-4, 4'-piperidin]-2(1H)-one derivatives with POCl₃ yielded 1, 2, 3, 4-tetrahydro-2, 9-diazaphenanthrene derivatives through a novel rearrangment. The reaction is suggested to processed via the formation of an isocyanate by dehydrative cleavage of the oxazinone ring with POCl₃. It was also found that treatment of 4-(2-methoxycarbonylamino-phenyl)-1, 2, 5, 6-tetrahydropyridine derivatives with trichlorosilane/triethylamine gave the corresponding 10-oxo-1, 2, 3, 4, 9, 10-hexahydro-2, 9-diazaphenanthrene derivatives.