Stereochemical Studies. XXIV. Asymmetric Synthesis of optically Active (+)-4-Methyl-4-phenyl-2-cyclohexenone with Enamine Alkylation using Proline Derivatives

Abstract

Alkylation of enamines prepared from 2-phenylpropanal and L-proline derivatives, with methyl vinyl ketone, was successful and gave, after hydrolysis and cyclization, optically active (+)-4-methyl-4-phenyl-2-cyclohexanone ((+)-IV). The effects of L-proline derivatives, solvents, and reaction temperature on the alkylation were discussed. Under selected conditions the optical yield reached about 50%. Asymmetric induction was clearly thermodynamically controlled.