DIASTEREOSELECTIVITY IN THE MICHAEL-TYPE ADDITION OF IMINES REACTING AS THEIR SECONDARY ENAMINE TAUTOMERS

Michael-type reactions of 2-methyl(benzylimino)cyclohexane (reacting a s its secondary enamine tautomer 1) were performed with methyl methacr ylate (2), methyl crotonate (5), and maleic anhydride (7). In each cas e, the stereochemical relationship of the substituents in the major cy clized adducts 4, 6, and 8 obtained with excellent diastereoselectivit ies was shown to be the one predicted in a previous theoretical calcul ation which established that the complex of the reactants has a chairl ike geometry. The predicted concomitant H-transfer and C-C bond format ion in these reactions was also confirmed in the methyl methacrylate c ase. Besides, these experiments have shown that regioisomers are forme d in appreciable amounts when substituted electrophilic olefins are us ed.