- Regioselectivity in the amination of azines: Reaction of pyrazine derivatives with O-mesitylenesulfonylhydroxylamine
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Treatment of 2-X-substituted pyrazines [X = H, Me, Et, Pr, i-Pr, t-Bu, MeCH(OH), H2N, AcNH] with O-mesitylenesulfonylhydroxylamine gave the corresponding 2-X- and 3-X-(1-amino)pyrazin-1-ium mesitylenesulfonates. 2-Alkylpyrazines (X = Me, Et, Pr, i-Pr) displayed a correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations and substituent steric constants. Wider series of substituted pyrazines [X = H, Me, Et, Pr, i-Pr, MeCH(OH), H2N, AcNH] conformed to a multiparameter correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations, on the one hand, and substituent constants σI, σR?, and E s?, on the other. The obtained data on the regioselectivity of amination of pyrazines were interpreted in terms of DFT/PBE/3Z quantum-chemical calculations. Pleiades Publishing, Ltd., 2011.
- Borodkin,Vorob'ev,Shakirov,Shubin
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experimental part
p. 889 - 896
(2011/10/02)
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- Regioselectivity in 2-X-pyrazine aminations by O-mesitylenesulfonylhydroxylamine
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The regioselectivity of 2-X-pyrazine aminations by O-mesitylenesulfonylhydroxylamine was studied experimentally and the results are discussed from the viewpoint of electronic and steric factors. DFT calculations are consistent with the reaction proceeding according to an SN2 mechanism.
- Borodkin, Gennady I.,Vorob'ev, Aleksey Yu.,Shakirov, Makhmut M.,Shubin, Vyacheslav G.
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supporting information; experimental part
p. 6779 - 6782
(2010/04/29)
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- Molecular and crystal structure of 1-amino-X-pyrazinium mesitylenesulfonates
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X-Ray diffraction analysis was performed of 1-amino-X-pyrazinium mesitylenesulfonates (X=H, 2-NH2, 3-NHCOMe, 3-OMe, 3-Cl). In all events save 1,2-diaminopyrazinium cation the bond length of N-NH2 was shorter than that of N-N bond but considerably longer than the length of the double bond N=N. In the 1,2-diaminopyrazinium cation the bond distance C 2-NH2 was close to the length of a common double bond C=N indicating the iminium character of the cation. Quantum-chemical calculations [AM1, PM3, DFT/(PBE/3z), B3LYP/6-31G++(2d,p)] provided the geometry of cations similar to the experimental one. In the crystals under investigation motifs were observed of 0D, 1D, and 2D type mainly due to hydrogen bonds N-H???O and π-stacking interactions of the aromatic rings.
- Andreev,Borodkin,Vorob'ev,Gatilov,Shubin
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p. 292 - 301
(2008/09/21)
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