Secondary enamines with electrophilic alkenes

The alkylation of acyclic imines with electrophilic alkenes such as acrylonitrile, methyl acrylate or phenyl vinyl sulphone is also sensitive to steric effects and again, as a consequence, only mono-alkylation occurs398. The regioselectivity of the reaction in methanol varied from 100% attack at the more substituted a-position to 70% attack at the less substituted a -position depending upon the steric inhibition manifested and the stabilization of the competing secondary enamine tautomers (vide infra) (Scheme 204). In contrast, the reaction of butanone and other methyl ketone imines with phenyl vinyl ketone occurs twice at the more substituted a-position but this is then followed by a double cyclization process (Scheme 205). Four carbon-carbon bonds are formed sequentially in this one-pot synthesis of the bicyclo[2.2.2]octanone 205 from acyclic precursors399,400. 

---