Stereochemical Behavior of Intermediary Compounds in the Amine-Catalyzed Knoevenagel Reaction

Article abstract of DOI:10.1246/bcsj.61.3211

Treatment of the active methylene compounds and aldehydes with a catalytic amount of a secondary amine produces thermodynamically stable alkenes, and the intermediary amino compounds are isolated.The reaction involves many reversible steps, and the stereochemistry of products is determined in the elimination step from the intermediary compounds via stable planar carbanions, in which the small difference in the steric requirements of two electron-withdrawing groups is effective.Steric and electronic effects in the intermediates sometimes bring about the carbon-carbon bond fission with recovery of active methylene compounds, and these effects prevent the Knoevenagel reaction from occuring.