Bibliographic Details
| Title: |
A new example of reversible thermal isomerization of 3 H-pyrazole into 4 H-pyrazole. |
| Authors: |
Vasin, V.1 vasin@mrsu.ru, Razin, V.2, Markelova, Yu.1, Masterova, Yu.1 |
| Source: |
Russian Journal of Organic Chemistry. Oct2015, Vol. 51 Issue 10, p1418-1422. 5p. 5 Diagrams, 1 Graph. |
| Subject Terms: |
*ISOMERIZATION, *PYRAZOLES, *ETHER (Anesthetic), *PHENANTHRIDINE, *INDAZOLES |
| Abstract: |
9-Diazofluorene reacted with phenyl prop-1-yn-1-yl sulfone in diethyl ether at 20°C (3-4 days) to give 5'-(benzenesulfonyl)-4'-methylspiro[fluorene-9,3'-pyrazole] (3 H-pyrazole) as the only 1,3-dipolar cycloaddition product formed according to the von Auwers rule. On heating in boiling ethanol for 0.5 h, 5'-(benzenesulfonyl)-4'-methylspiro[fluorene-9,3'-pyrazole] underwent partial reversible isomerization into a 4 H-pyrazole derivative, 3-(benzenesulfonyl)-3a-methyl-3a H-dibenzo[ e, g]indazole, whereas in toluene at 180°C (40 min) it was completely converted into thermodynamically more stable 2-(benzenesulfonyl)-3-methylpyrazolo[1,5- f]phenanthridine with a 1 H-pyrazole fragment. 3a-Methyl-2 H-dibenzo[ e, g]indazol-3(3a H)-one was formed when the 3 H- and 4 H-pyrazoles were kept in glacial acetic acid at 20°C in the presence of a catalytic amount of sulfuric acid, followed by treatment with water. Alcoholic potassium hydroxide promoted reversible isomerization of the 3 H-pyrazole into 5'-(benzenesulfonyl)-4'-methylidene-2',4'-dihydrospiro[ fluorene-9,3'-pyrazole]. [ABSTRACT FROM AUTHOR] |
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| Database: |
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