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Solid SiO2:H3PO4 acid catalyzed solvent-free cyclization of aryl 2-propen-1-ones: Synthesis of some 1-thiocarbomyl pyrazolines and spectral correlations of some 3-phenyl-5-(substituted phenyl)-4,5-dihydro-1H-pyrazole-1-carbothioamides

Ganesamoorthy Thirunarayanan, Krishnamoorthy Guna Sekar

In the present study we have synthesized some 1-thiocarbomyl pyrazolines including 3-phenyl-5-(substitutedphenyl)-4,5-dihydro-1H-pyrazole-1- carbothioamides using solvent free SiO2:H3PO4 catalyzed cyclization of chalcones with thiosemicarbazide under microwave irradiation. The yields of the 1H-pyrazole-1-carbothioamides are more than 85%. The synthesised pyrazole-1-carbothioamideswere characterized by their analytical, physical and spectral data. The infrared íC=N, C=S, NH (cm-1) frequencies, NMR chemical shifts (ä, ppm) Ha, Hb, Hc, C=N, C=S of synthesised 3-phenyl-5- (substitutedphenyl)-4,5-dihydro-1H-pyrazole-1-carbothioamides were correlated with Hammett substituent constants, F and R parameters. From the results of statistical analyses the effects of substituent on the above functional group of pyrazole-1-carbothiamides.