1H NMR Studies of Proton Transfer and ?-Complex Formation in the Reactions of N-Substituted Picramides with Oxygen and Nitrogen Bases

Article abstract of DOI:10.1002/mrc.1270130613

1H NMR measurements of N-substituted picramides in dimethyl sulphoxide-methanol containing sodium methoxide show that the two major modes of 1:1 interaction involve transfer of an amino proton to give the conjugate base or methoxide attack at the 3-position to give a ?-adduct.The proportion of parent reacting by the latter pathway increases as the proportion of methanol in the solvent increases.Some comparative measurements in isopropanol-dimethyl sulphoxide show that relative to methoxide the isopropoxide ion has a greater propensity abstraction than for base addition.Reaction of the substrates with amide ions derived from piperidine or from benzylamine gives ?-complexes by attack at unsubstituted ring positions.In the benzylamide adducts spin coupling is observed between the amino proton and the adjacent ring and methylene protons.