Derivatives of arylhydrazonic acids. Part 3: Stereochemical rearrangement of Z-oxanilo-N-dialkyl-N-arylamidrazones

Oxanilo-N¹-dialkyl-N²-arylamidrazones have been prepared by nucleophilic substitution of the chloride function of appropriate hydrazonoyl chlorides. Relative stabilities of Z- and E-isomers, calculated with the RHF/6-31G^∗ ab initio method, range between 0.7 and 2.1 kcal/mol. The Z-isomer is detected to be thermodynamically more stable for studied compounds. X-ray structure determination of 2-dimethylamino-N-phenyl-2-phenylhydrazonoacetamide revealed E- and Z-isomers (ratio 1:1) in the crystal. The different intra- and intermolecular hydrogen bond interactions, which are identified in solid state of compounds, are dissolved in polar solvents. All compounds were found to form E/Z-equilibrium in solution. In some cases E-isomers could be separated and fully characterized.