Enantioselective Synthesis of 4‐Hydroxytetrahydropyridine Derivatives by Intramolecular Addition of Tertiary Enamides to Aldehydes

Stable tertiary enamides and enecarbamates undergo highly enantioselective intramolecular nucleophilic addition to aldehyde units catalyzed by chiral binol–Ti complexes under mild conditions to produce the title compounds in up to 99.5 % or greater enantiomeric excess. A positive nonlinear effect was detected and the formation of binol–Ti aggregates suggests an intricate asymmetric catalytic pathway.