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Paper | Regular issue | Vol 83, No. 7, 2011, pp.1567-1585
Published online, 10th May, 2011
DOI: 10.3987/COM-11-12206
Reactions and Tautomeric Behavior of 1-(2-Pyridinyl)-1H-pyrazol-5-ols

Peter Pfaffenhuemer, Christian Laggner, Stefan Deibl, Barbara Datterl, and Wolfgang Holzer*

*Department of Drug and Natural Product Synthesis, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria


The tautomeric behavior of 1-(2-pyridinyl)-2-pyrazolin-5-one (1a) and its 3-methyl derivative (1b) in different solvents was investigated by means of NMR spectroscopy (1H, 13C, 15N). Moreover, studies regarding the reactions of the title compounds with trimethylsilyldiazomethane, carboxylic acid chlorides, different orthoesters, dimethylformamide diethyl acetal and benzaldehyde are presented. Involvement of pyridine-N atoms in hydrogen bondings was investigated by means of 15N-NMR spectroscopy.