Correlation of proton shifts of pyrazines with substituent constants was written by Marx, Gerard S.;Spoerri, Paul E.. And the article was included in Journal of Organic Chemistry in 1972.Electric Literature of C7H8N2O2 This article mentions the following:
A study of the PMR spectra of monosubstituted pyrazines in Me2SO indicated that the assigned peak values of the ortho, meta, and para protons correlated quite well with substituent constants A substituent-ring second-order mesomeric interaction explains the correlation of the proton meta to electron-donating substituents. In the experiment, the researchers used many compounds, for example, Ethyl pyrazine-2-carboxylate (cas: 6924-68-1Electric Literature of C7H8N2O2).
Ethyl pyrazine-2-carboxylate (cas: 6924-68-1) belongs to pyrazine derivatives. Pyrazine is an N-heterocyclic moiety, and it can be easily prepared from ethylenediamine and 1,2-diketone, α-hydroxyketone, α-methyl ketone. Pyrazines undergo nearly all of the same reactions as pyrimidines, from nucleophilic substitution (SNAr) to palladium-catalyzed cross coupling reactions.Electric Literature of C7H8N2O2