Catalytic Effect of Amines on the Knoevenagel Condensation of p-Nitrophenylacetic acid with m-Nitrobenzaldehy de

Abstract

The Knoevenagel condensation of p-nitrophenylacetic acid [1] with m-nitrobenzaldehyde [2] was carried out in the presence of amines such as piperidine, diethylamine, triethylamine, pyrrolidine, morpholine, N-ethylmorpholine, etc. trans-3, 4'-Dinitrostilbene [3], 1-(m-nitrophenyl)-2-(p-nitrophenyl)ethanol [4], and α-(p-nitrophenyl)-m-nitrocinnamic acid [5] were isolated. The {[3]+[5]}/[4] ratio varied greatly with the amine used, because of its steric hindrance. [3] also was obtained by the dehydration of [4] with small amounts of concentrated sulfuric acid in 96% yield and by the decarboxylation of [5] with pyrrolidine in 90% yield. A probable reaction pathway was discussed.