Obtenção e estudo da reatividade de ciano-acrilatos de etila e compostos relacionados com ênfase na síntese de N- e O-heterociclos

Abstract

This work reports the results of the reactivity study of the ethyl cyano-acrylates (3), obtained from the Horner-Wadsworth-Emmons (HWE) olefination reaction applied to α,β-unsaturated ketones (1) with diethyl (cyanomethyl)phosphonate (2). Eight examples of 6-aryl-4-ethoxycarbonyl-2H-pyran-2-ones (4) were synthesized by the autocondensation reaction of ethyl 4-aryl-2-(cyanomethylene)-4-methoxy-but-3-enoates (3), under reflux of water in the presence of hydrochloric acid, furnishing the products with yields from 15% to 66%. An unprecedented series of six 7-akyl-5-cyanomethyl-3,4,7,7a-tetrahydropyrano[2,3-b]pyrrol-6(2H)-ones (6) was synthesized by the reaction of ethyl 3-cyano-2-(3,4-dihydro-2H-pyran-5-yl)acrylate (3) with primary amines (5), without catalysts in a solvent-free condition, giving yields from 55% to 75%. It was observed that the ethyl 2-(4,5-dihydrofuran-3-yl)-2-oxoacetate (1j) undergoes a spontaneous rearrangement with the formation of ethyl 3-formyl-4,5-dihydrofuran-2-carboxylate (7). Subsequently, it was studied the ideal conditions for the controlled conversion of compound 1j to 7. The unprecedented compound 7 was submitted to the olefination reaction with diethyl (cyanomethyl)phosphonate, which afforded ethyl 3-(2-cyanovinyl)-4,5-dihydrofuran-2-carboxylate (8). The reactivity of compound 8 was studied by performing reactions with primary amines, which resulted in a series of five carboxamides (9) with yields from 45% to 90%. The compound 7 was also reacted with hydrazines, using alcohols as solvent. As a result it was obtained a new series of 7-alkoxy-2,3-dihydrofuro[2,3-d]pyridazines (13) with yields from 33% to 70%. All synthesized compounds were characterized by nuclear magnetic resonance and mass spectrometry.