Synthesis and structural characterization of pyrazol-1′-ylpyrazolo[1,5-a]pyrimidines by multinuclear NMR spectroscopy
作者:Ranjana Aggarwal、Garima Sumran、Rosa M. Claramunt、Dionisia Sanz、J. Elguero
DOI:10.1016/j.molstruc.2009.06.021
日期:2009.9
3(5)-Amino-5(3)-hydrazinopyrazole dihydrochloride (8) reacts with pentane-2,4-dione (9a) to afford 2-(3',5'-dimethylpyrazol-1'-yl)-5,7-dimethylpyrazolo[1,5-a]pyrimidine (10a) instead of the 3-(3',5'-dimethylpyrazol-1'-yl)-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine isomer (11). Similarly, the reaction of 8 with phenyl-1,3-butanedione (9b) resulted into the formation of 2-(3'-methyl-5'-phenylpyrazol-1'-yl)-5-methyl-7-phenylpyrazolo[1,5-a]pyrimidine (10b) out of the four possible regioisomers. The structure of the reaction products 10a and b was established by analysis of high-resolution (1)H NMR spectra. Complete spectral analysis has been achieved utilizing ((1)H-(13)C) HMQC as well as ((1)H-(13)C) and ((1)H-(15)N) HMBC experiments. (c) 2009 Elsevier B.V. All rights reserved.