NITRO ENOL, 3-HYDROXY-4-NITRO-5-PHENYL-3-PYRROLIN-2-ONE, AND ITS REACTIVE METHYL ETHER

A completely enolized cyclic α-nitro ketone, 3-hydroxy-4-nitro-5-phenyl-3-pyrrolin-2-one (5a), was prepared by means of the base-catalyzed cyclization of ethyl N-(1-phenyl-2-nitroethyl)oxamate (4). The nitro enol, a very strong acid, was the only tautomer which could be detected. The enol underwent facile ring cleavage as a result of nucleophilic attack by water or amines at the 3 position. Methylation of the nitro enol with diazomethane yielded the methyl enol ether, 3-methoxy-4-nitro-5-phenyl-3-pyrrolin-2-one (8). The product was shown to be the enol ether rather than the isomeric keto nitronic ester by sodium borohydride reduction to 3-methoxy- 4-nitro-5-phenylpyrrolidin-2-one (10) followed by stannous chloride reduction to 4-amino-3-methoxy-5-phenylpyrrolidin- 2-one (13). The nitro enol ether (8) reacted rapidly with ammonia and with primary or secondary amines to yield 3-amino-4-nitro-5-phenyl-3-pyrrolin-2-ones (9,11, or 12). © 1969, American Chemical Society. All rights reserved.