DIASTEREOSELECTIVITY AND ENANTIOSELECTIVITY IN THE ADDITION OF CHIRALIMINES OF 2-METHYLCYCLOHEXANONE TO CROTONIC AND METHACRYLIC-ACID ESTERS

Additions of the chiral imine (reacting as its secondary enamine tauto mer) obtained from (S)-1-phenylethylamine and 2-methylcyclohexanone we re performed with the phenyl ester of crotonic and methacrylic acid as well as with their methyl ester. In each example, the stereochemical relationship of the substituents in the major adduct was shown to be t he one predicted in a previous theoretical calculation which establish ed that the reactants complex has a chairlike geometry. In all the exa mples, the diastereoselectivity is superior to 98%. The enantioselecti vity of the reactions is excellent as is usually the case with unsubst ituted electrophilic olefins, the example with phenyl methacrylate bei ng particularly remarkable (de and ee > 99%). In each case the favored diastereofacial selectivity is again in accordance with the rule elab orated previously. Relevant facts about the influence of the substitue nts upon the reactivity, the proportion of regioisomers, the stereosel ectivity, and the enantioselectivity of the reaction are given.