| Autor: |
Hockstedler, Amy N., Edjah, Beatrice A., Azhar, Saajid Z., Mendoza, Hadrian, Brown, Nicole A., Arrowood, Hayley B., Clay, Andrew C., Shah, Anand B., Duffek, Glenda M., Jianmei Cui, Baumstark, Alfons L. |
| Předmět: |
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| Zdroj: |
Heterocyclic Communications; Apr2017, Vol. 23 Issue 2, p125-131, 7p |
| Abstrakt: |
A series of chalcones 1-12 were converted to pyrazolines (1Pi-12Pi) by reaction with phenylhydrazine followed by DDQ oxidation to produce the corresponding pyrazoles (1Pz-12Pz). Three 1-phenyl-3-t-butyl-5-arylpyrazoles (13Pz-15Pz) were synthesized using an analogous approach. Molecular modeling studies predicted the 5-aryl group of the pyrazoles for both series to have a torsion angle of 52°-54° whereas the 1-phenyl group was predicted to have 35°-37° torsion angles. The 3-aryl group was predicted to be essentially coplanar (-3°) with the pyrazole system in the first series. 13C NMR data for both series, 1Pz-12Pz and 13Pz-15Pz, were collected in DMSO-d6 at 50°C. A plot of the C4 chemical shifts for 1Pz-12Pz versus Hammet constants for 5-aryl substituents yielded a very good linear correlation (R² = 0.96) with a slope of 1.5. The chemical shift data for C4 showed little or no depend- ence on 3-aryl substituents. The result for 13Pz-15Pz, despite only three points, was consistent with the first series results and yielded a ρ value of 2.0. Distal transmission of substituent effects (5-aryl groups) to C4 of the pyrazole system was reduced by roughly 50-60% of that of the analogous planar isoxazole system, but are not consistent with results for the similarly twisted 4-bromoisoxazoles. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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