E. S. Domnina

Interaction of 1-vinylpyrazoles with alkanethiols

It was found that vinylpyrazoles react with thiols both according to ionic and according to free-radical mechanisms, with the formation of products of α- and β-addition. Radical thiylation of 1-vinylpyrazoles is a convenient method of synthesis of pyrazoles with sulfur-containing substituents.

Hydrohalogenation of 1-vinylpyrazoles

Conclusions1.In accordance with Markownikoffs rule, at 20–25°C 1-vinylpyrazole and 4-bromo-1-vinylpyrazole add predominantly hydrogen halides at the double bond of the vinyl group. Under these conditions, formation of the corresponding hydrohalides is characteristic of the more basic alkyl-substituted 1-vinylpyrazoles.2.Addition of hydrogen halides to 1-vinylpyrazoles at 0–15°C occurs only at the N2 atom with formation of salts.

Direct13C-1H coupling constants in the vinyl group of 1-vinylpyrazoles

ConclusionsThe13C-1H direct coupling constants in the vinyl group of 1-vinylpyrazoles are stereo-specific and vary with change in the conformer ratio.

NMR and IR spectroscopic study of the structure of quaternary salts of 1-vinylpyrazoles

ConclusionsIR and NMR spectral analysis indicated that quaternization of 1-vinylpyrazoles leads to a decrease in conjugation between the heterocycle and the vinyl group and to a significant leveling out of the charges on the atoms in the heterocycle and vinyl group.

NMR Spectra and structure of 1-vinylpyrazoles

ConclusionsA1H and13C NMR spectral analysis permitted evaluation of electronic and steric effects in 1-vinylpyrazoles. 5-Methyl-1-vinylpyrazoles have predominantly S-cis-N2 orientation, while 1-vinylpyrazoles without substituents at C5 are conformer mixtures.

Long-range spin-spin coupling and relative orientation of vinyl group in 1-venylpyrazole

ConclusionsOn the basis of the experimental values of the long-range spin-spin coupling constants of the protons it was established that in 1-vinylpyrazole and its 4-bromo derivative the vinyl group has predominantly a trans orientation relative to the nitrogen in the 2 position.

Use of Eu(DPM)3 to study the long-range spin-spin coupling of1H-1H and1H-14N via the PMR spectra

Employing heteronuclear double resonance and paramagnetic additives it was established that the additional broadening of the signals in the PMR spectrum of 1-vinylimidazole is caused by the1H -14N spin-spin coupling, while in the spectrum of 1-vinylpyrazole it is caused, in addition, by the long-range1H-1H spin -spin coupling via six bonds.

Removal of spin-spin coupling in NMR spectrum of N-vinylpyrazole by paramagnetic additives

An explanation is given for the change in the multiplicity of the signals of the protons of the vinyl group in the NMR spectrum of 1-vinylpyrazole, taken with the addition of a nickel salt.

NMR of N-vinyl-2-methylimidazole in presence of paramagnetic Co2+ and Ni2+ ions

The insertion of a methyl group into a heteroring expands the possibilities of the method of paramagnetic additives.

Peculiarities of the chlorination of vinylindole in halogenation reactions

1. n nWe were the first to study the halogenation of vinylindole. Chlorination of the compound yields diindolyl-N, N-(α,α-dichloro)butane. n n n n n2. n nThe product formed in the first stage of the bromination of vinylindole is 1-(α,β -dibromo)ethylindole, while 1-(α,β,β-tribromo)ethylindole is obtained when excess bromine is used.