PMR spectra of 2-substituted pyrazines and the corresponding pyrazine N-oxides and N,N′-dioxides |
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Authors: | G P Syrova Yu N Sheinker I S Musatova A S Elina |
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Institution: | (1) S. Ordzhonikidze All-Union Scientific-Research Institute of Pharmaceutical Chemistry, Moscow |
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Abstract: | The PMR spectra of pyrazine, its 2-substituted derivatives, and the corresponding N-oxides and N,N -dioxides were investigated. The character of the change in the chemical shifts in the N-oxides and N,N -dioxides of unsubstituted pyrazine indicates the electron-donor effect of the N O group. An additive effect of the N O groups on the chemical shifts of the ring protons is observed in pyrazine N,N -dioxide. An appreciable interaction of the substituent with the N(1) O group and a weak interaction with the N(4) O group occur in N-oxides and N,N -dioxides of 2-substituted pyrazines. A significant increase in the ortho and meta spin-spin coupling constants of the ring protons is noted when the nitrogen atoms are oxidized. The sign of the spin-spin coupling constant (J35) through the N O group was determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 266–273, February, 1972. |
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