Imidate Anions: Stereochemistry, Equilibrium, Nitrogen Inversion, and Comparison with Proton Exchange

Article abstract of DOI:10.1021/jo00209a011

Soluble imidate anions, especially formimidate anions, HC(O^-)=NR, can be prepared by treating the amide with NaH or KH in THF or Me2SO.N-Phenylformimidate anion can also be prepared in hydroxylic solvents by treating the amide with excess NaOH.The imidate anions have been characterized by proton NMR.The E stereoisomer is generally more stable than the Z, but the E/Z equilibrium constant is strongly solvent dependent.The results are compared with previous studies of base catalyzed proton exchange.According to saturation-transfer measurements, the barrier to nitrogen inversion in these imidate anions is 19-23 kcal/mol.The imidate anions could be protonated by trifluoroethanol to regenerate the amide as a nonequilibrium E/Z mixture, which then returned to equilibrium at a measurable rate.