The conversion of 2,x-disubstituted cyclohexanones to their less stable isomers-the stereochemical implications of enamine hydrolysis

When 2-methyl-x-alkylcyclohexanones (x≠2) are converted to their enamines and the latter are hydrolysed under kinetic conditions the process leads to a substantial increase in the proportion of the less stable ketone, over that present at equilibrium. Pyrrolidine appears to be the most effective amine in this process. Hydrolysis of the enamine isomer having a tetrasubstituted double bond proceeds with little or no stereoelectronic control during the protonation step. Low temperature thermal isomerization of simple enamines is shown not to exist; when equilibration does occur, it is due to traces of acid impurity.