3-Phenylpyrazolo(4,3-c)pyridine and derivatives: structure determination |
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| Institution: | 1. Division of Cardiovascular Diseases and Hypertension, Rutgers University Robert Wood Johnson Medical School, New Brunswick, NJ;2. Center for Translational Metabolism and Health, Department of Preventive Medicine and Division of Cardiology, Northwestern University Feinberg School of Medicine, Chicago, IL;3. Division of Nephrology, Duke University School of Medicine, Durham, NC;4. Departments of Medicine and Epidemiology, University of Alabama, Birmingham, AL;1. Institute for Computational Physics, University of Stuttgart, D-70569 Stuttgart, Germany;2. Digitalization Development Biologicals CMC, Boehringer Ingelheim Pharma GmbH & Co. KG, D-88397 Biberach (Riss), Germany;3. Analytical Development Biologicals, Boehringer Ingelheim Pharma GmbH & Co. KG, D-88397 Biberach (Riss), Germany;4. University of Applied Sciences Biberach, D-88400 Biberach (Riss), Germany |
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| Abstract: | The structures of 3-phenylpyrazolo(4,3-c)pyridine (1) and 5-methyl-3-phenyl-4,5,6,7-tetrahydropyrazolo(4,3-c)pyridine (2) are determined by detailed 1H and 13C NMR analysis and theoretical calculations in comparison with their N-methyl derivatives as fixed models. CNDO/2 and PPP calculations are performed on the three prototropic forms admissible for the tautomeric system 1. By comparison of the 13C NMR and UV spectra of 1 with those of its three fixed N-methyl derivatives and of the UV spectra calculated for the tautomers of 1 with that experimentally obtained in the range 200–450 nm, 3-phenylpyrazolo(4,3-c)pyridine (1) is established to exist entirely in the 1H tautomeric form 1A.By 13C NMR investigations of 5-methyl-3-phenyl-4,5,6,7-tetrahydropyrazolo(4,3-c)-pyridine (2), in comparison with its fixed 1-methyl-1H derivative 9 and other substituted pyrazoles, 2 is determined to be a mixture of the 1H- (2A) and 2H- (2B) tautomers with 2A largely predominating. The compounds investigated are described here for the first time. |
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