PREPARATION OF STABLE PRIMARY ENAMINES - 1-AMINOBUTADIENES BY ALLYL GRIGNARD ADDITION TO ARYL CYANIDES FOLLOWED BY CONTROLLED HYDROLYSIS

From thermochemical data it is suggested that 1-aminobutadienes are mo re stable than their nonconjugated imine tautomers by about 2 kcal mol (-1). High level ab initio calculations have established the thermodyn amic preference of the conjugated primary enamines over their beta,gam ma-unsaturated ketimine isomers in the gas phase. This general predict ion of an increased stability of primary enamines by butadiene conjuga tion has been confirmed experimentally with a variety of representativ e examples. Allyl Grignard addition to a number of aryl or hetaryl cya nides followed by controlled hydrolysis yields the respective beta,gam ma-unsaturated ketimine systems that subsequently rearrange completely to their 1-aminobutadiene isomers. Rearrangement to the thermodynamic ally more favored alpha,beta-unsaturated imine tautomers is kineticall y inhibited and, hence, not observed in these systems. In some cases c onjugated enamine formation is already observed at the stage of the or ganometallic intermediates.