STEREOCHEMISTRY OF AMINOLYSIS OF N-PENTAFLUOROPHENYLCARBONIMIDOYL DICHLORIDE - CRYSTAL AND MOLECULAR-STRUCTURES OF N2-PENTAFLUOROPHENYL-N1,N1-DIBENZYLCHLOROFORMAMIDINE

It has been established that the product of the reaction of N-pentaflu orophenylcarbonimidoyl dichloride (1) wit dibenzylamine, viz. -pentafl uorophenyl-N1,N1-dibenzylchloroformamidine (4a) is a Z-isomer, whereas according to the concept of stereoelectronic control one might have e xpected a product with E-configuration. The heat of formation and the geometry of Z- and E-isomer of 2-pentafluorophenyl-N1,N1-diethylchloro formamidine (4b) (the latter is a product of the reaction of 1 with di ethylamine) were calculated with the semi-empirical MNDO method. The c alculated geometry of (Z)-4b was found to be in a good agreement with the experimentally determined structure of 4a. The formation of (Z)-4b is more preferable energetically than that of (E)-4b; the calculated difference in the heats of formation is 2.8 kcal mol-1. Thermodynamic control of the reaction stereochemistry is proposed.