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

摘要

Michael-type reactions of 2-methyl(benzylimino)cyclohexane (reacting as its secondary enamine tautomer 1) were performed with methyl methacrylate (2), methyl crotonate (5), and maleic anhydride (7). In each case, the stereochemical relationship of the substituents in the major cyclized adducts 4, 6, and 8 obtained with excellent diastereoselectivities was shown to be the one predicted in a previous theoretical calculation which established that the complex of the reactants has a chairlike geometry. The predicted concomitant H-transfer and C-C bond formation in these reactions was also confirmed in the methyl methacrylate case. Besides, these experiments have shown that regioisomers are formed in appreciable amounts when substituted electrophilic olefins are used. [References: 20]