Li-qun Shen, Su-Yu Huang, K. Diao
Aug 15, 2012
Citations
1
Influential Citations
16
Citations
Journal
Journal of Molecular Structure
Abstract
Abstract Two new pyrazole derivatives of 1-(6-chloro-pyridin-2-yl)-5-hydroxy- 1H -pyrazole-3-carboxylic acid methyl ester 1a and 5-acetoxy-1-(6-chloro-pyridin-2-yl)- 1H -pyrazole-3-carboxylic acid methyl ester 2 were synthesized and characterized by 1 H, 13 C NMR, IR spectroscopies and HRMS analyses. The molecular structure of 1a and 2 were studied by X-ray diffraction and compared to density-functional-theory (DFT) calculations. The gauge-including atomic orbital (GIAO) method for calculating 1 H and 13 C NMR nuclear magnetic shielding tensors at the DFT method with 6-31+G * basis set were applied to the compounds 1a and 2 . Additionally, thermodynamic properties of the cyclization of the compound 3 to these compounds ( 1a, 1b, 1c, 4 ) were investigated by theoretical calculations. These theoretical calculations was shown that the compound 1a was readily formed and was the most stable one. Tautomeric forms of the compound 1a were optimized at the same methods and basis set. The calculated relative Gibbs free energies of the tautomeric forms of 1a were used to estimate the equilibrium constants. It was shown that the 1a was the most stable than tautomer of 1b and 1c in the gas phase.