Kinetic and Stereochemical Study on Bimolecular Substitution Reactions of Hydrazonates, Thiohydrazonates, and Hydrazonoyl Chlorides with Methoxide Ion

Article abstract of DOI:10.1021/jo00191a008

Reaction of the (Z)-hydrazonoyl chlorides 2 with methoxide ion in methanol, under conditions where kinetic results show the reaction is bimolecular, leads to stereospecific formation of the (Z)-methyl hydrazonates 5.Less than 2percent of the product with the "inverted" configuration at carbon (6) is formed.When a poorer leaving group than Cl(-) is involved, then mixtures of E and Z products result.Thus the aryl thiohydrazonates (3) which have the Z configuration give 84-90percent of the (Z)-methyl hydrazonate on reaction with methoxide ion.The (E)-aryl hydrazonates undergo reaction ca. 12-fold more slowly and isomer ratios of the (Z)- and (E)-methyl hydrazonates which result are closer to 1:1.The product methyl hydrazonates 5 and 6 undergo MeO(-)-catalysed interconversion to an equilibrium mixture which favors 6, but at a slower rate than the formation of either 5 or 6.The stereochemical outcome of these displacements at the C=N bond is rationalized in terms of stereoelectronic control of the addition and elimination steps.