Alternative Formation of Products of Direct or Cine Methoxydenitration of 1-Alkyl-3,4-dinitropyrroles

1-Alkyl-3,4-dinitropyrroles 1 with methoxide ion in refluxing methanol yield trans-1-alkyl-4,5-dimethoxy-3-nitro-2-pyrrolines 2. The acid-promoted elimination of methanol from 2 is regioselective, yielding 1-alkyl-2-methoxy-4-nitropyrroles 3, whereas the base-promoted elimination, under heterogeneous conditions, yields regiospecifically 1-alkyl-3-methoxy-4-nitropyrroles 5. Acid-promoted reactions in ethanol or CD3OD indicate the fast exchange of one alkoxy group of pyrrolines 2, probably as a consequence of the ready formation of a cationic σ-adduct. © 1979 American Chemical Society.