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- Title
Synthesis and van Alphen-Hüttel rearrangement of substituted 3 H-pyrazoles, adducts of 1,3-dipolar cycloaddition of 9-diazofluorene and diphenyldiazomethane to trimethyl(tosylethynyl)silane.
- Authors
Vasin, V.; Markelova, Yu.; Bezrukova, E.; Petrov, P.; Razin, V.
- Abstract
Trimethyl(tosylethynyl)silane reacted in ethyl ether at 20°С with diphenyldiazomethane affording 3 Н-pyrazole, a product of 1,3-dipolar cycloaddition against Auwers rule. The reaction with 9-diazofluorene is less selective, but its regioselectivity is also governed by the steric effect of the bulky trimethylsilyl substituent at the triple bond С≡С. The adduct with diphenyldiazomethane at boiling in methanol or keeping in glacial acetic acid in the presence of a catalytic quantity of conc. HSO undergoes the Van Alphen-Hüttel rearrangement by the migration of the phenyl substituent to the atom N in the 1 Н-pyrazole. The same 1 Н-pyrazole together with a product of nitrogen elimination, trimethylsilyl substituted cyclopropane, is formed in the 2: 1 ratio at boiling in benzene. A similar behavior is observed in the glacial acetic acid for the anti-Auwers adduct of 9-diazofluorene. It suffers nitrogen elimination at boiling in benzene converting in spirocyclic cyclopropene. The Auwers adduct of 9-diazofluorene at boiling in methanol transforms due to the van Alphen-Hüttel rearrangement into the corresponding 4 Н-pyrazole that undergoes a hydrodesilylation to give a derivative of 1 Н-pyrazole, 3-tosyl-1(2) H-dibenzo[e,g]indazole.
- Subjects
HETEROCYCLIC compounds synthesis; PYRAZOLES; REARRANGEMENTS (Chemistry); CHEMICAL adducts; RING formation (Chemistry); FLUORENE; METHANE derivatives; METHYLSILANE
- Publication
Russian Journal of Organic Chemistry, 2016, Vol 52, Issue 11, p1632
- ISSN
1070-4280
- Publication type
Article
- DOI
10.1134/S1070428016110142