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Part-IResults and Discussion3.1.1b Treatment of Aldehydes or Ketones with Alkyl Cyanoacetates and ElementalSulfurThis method involves a one pot procedure which is extensively used for the synthesis ofnumerous 2-amino-3-carbonylthiophenes. 19-21 Here, the methodology involvescondensation of methyl aldehydes, methyl ketones, or 1,3 dicarbonyl compounds withactivated acetonitriles such as malonitrile, cyanoacetic ester, cyanoacetamide and its N-substituted derivatives, hetroarylacetonitriles, α-cyanoketones & sulfur in presence of asecondary or tertiary aliphatic amine at room temperature. Ethanol, dimethylformamide,dioxane, excess ketone such as methyl ethyl ketone or cyclohexanone are preferredsolvents, while the 2 o or 3 oamines employed may be diethylamine, morpholine ortriethylamine. Only 0.5-1.0 molar equivalents of the amine, based on the amount ofnitrile is used. The yields of the product are much higher by this method (Scheme-3).OR 2 + X CNR 1SAmineR 1 , R 2 = H, alkyl, aryl, cycloalkyl,heteroarylX = CN, COOMe, COOEt, COPh, CO-heteroaryl, CONH 2Scheme 3R 2R 1SXNH 2Alternatively, a two step procedure is preferable. An, α, β-unsaturated nitrile is firstprepared through Knovenagel condensation of the carbonyl compound and an activemethylene nitrile and then treated with sulfur and amine (Scheme-4). This two stepversion of the Gewald reaction gives higher yields. Even more important is that certainketones such as alkyl aryl ketones, do not give thiophene in the one pot-modification, 22,23but give acceptable yields by this two-step technique (Scheme-4).68