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Part-IResults and DiscussionOR 1XR 1XR 2R 1XCNR 2S/Base-BHR 2R 1 , R 2 N= H, alkyl, aryl, cycloalkyl,heteroarylX = CN, COOMe, COOEt, COPh, CO-heteroaryl, CONH 2SSN-H x SR 1XR 1XR 1XB -R 2SNH 2R 2HSNH-BHR 2HSNHScheme-4. Mechanism for Scheme-3Both of these one and two steps variants have been employed out with numerous ketonesand aldehydes and active methylene nitriles. Cyclic and heterocyclic ketones have beenused extensively. It was however, observed that significantly lower yields (40-65%) wereobtained with cyclic ketones having rings larger than six-membered. This trend issuggestive of increasing non-bounded repulsive interaction between methylene protonsin middle and large sized rings fused to a planar five membered rings. 243.1.1c Cyclization of Acryonitriles with Elemental SulfurAcryonitriles, obtained through the condensation of aldehydes or ketones with alkylcyanoacetates, using either diethylamine or morpholine, get cyclized into substituted 2-aminothiophenes through the action of ‘S’ in presence of a 2 o amine. (Scheme-5)XR 1XR 1R 2CNS2 o amineR 2SNH 2R 1, R 2 = H, alkyl, aryl, cycloalkyl, heteroarylX = CN, COOMe, COOEt, COPh, CO-heteroaryl, CONH 2 ,Scheme-53.1.1d Treatment of Enamines with Alkyl Cyanoacetates and Elemental SulfurEnamines derived from ketones and 2 o aliphatic amines like morpholine or piperidineundergo the Gewald reaction with activated acetonitriles and elemental sulfur to give 2-aminothiophenes (Scheme-6).69