Furan Derivatives 90. A New Nucleophilic Substitution in Furan Series

Abstract

The Knoevenagel condensation of 5-arylthio-, 5-heteroarlthio- and 5-arylsulphonyl-2-furaldehydes, respectively, with malonitrile in ethanol in the presence of basic catalysts (sodium ethoxide) gives rise to corresponding α, β-unsaturated compounds¹. Now, we have found a different course of the condensation, when saturated heterocyclic secondary amines (piperidine, morpholine, pyrolidine and N-methylpiperazine) as catalysts were used. In the first step of this reaction the normal condensation product i.e. 2-cyano-3-(5-arylthio-2-furyl)-, 2-cyano-3-(5-heteroarylthio-2-furyl)- and 2-cyano-3-(5-arylsulphonyl-2-furyl) acrylonitrile is formed which further reacts according to the S_N mechanism with the present secondary amine to the appropriate 5-aminoderivative. In order to increase the yields of reaction products, the condensation was carried out with equimolar amounts of aldehyde, malonitrile and secondary amine in absolute ethanol at room temperature (Reaction 1).