Experimental and quantum-chemical calculations on some 1H-pyrazole-3-carboxamide and -3-carboxylate derivatives formation

The 1H-pyrazole-3-carboxylic acid was converted via reactions of its acid chloride 1 with various binucleophiles like 1,2-diaminoethane (2a), 1,2-diaminopropane (2b) and 2-amino-2-methylpropanol (2c) into the corresponding 1H-pyrazole-3-carboxamides and -3-carboxylate 3a–c, respectively, in good yields (66–95%). The reactions of 1 with aliphatic diamines and amino alcohols (2a–c) in benzene for 5–6 h with catalytic amounts of pyridine lead to the products 3a–c formation. The structures of these new synthesized compounds were determined from the 13C NMR, 1H NMR, IR spectroscopic data and elemental analyses. All of them were compared with their previous analogs. The mechanism of reaction between 1 and 2a–c was studied by means of semi-empirical AM1 calculations. q 2005 Elsevier B.V. All rights reserved.