Mechanism of E/Z Stereoisomerization of Imidate Anions

Article abstract of DOI:10.1021/jo00265a010

Kinetics of E/Z stereoisomerization of N-arylformimidate anions, HC(O^-)=NAr, in N-methylpropionamide solvent were determined by an NMR saturation-transfer method.A Hammett plot of the rate constans gives a slope ρ of +2.3 +/- 0.2 or +2.1 +/- 0.3.This value is very close to the ρ of 2.2 observed in similar imine stereoisomerizations know to proceed by nitrogen inversion.It is inconsistent with the ρ of 3.8 expected for stereoisomerization by C-N rotation.It is therefore concluded that E/Z stereoisomerization of imidate anions proceeds by nitrogen inversion, despite a high-level MO calculation that favored C-N rotation.