Regioselectivity in the amination of azines: Reaction of pyrazine derivatives with O-mesitylenesulfonylhydroxylamine

Abstract

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 sub- stituted pyrazines (X = H, Me, Et, Pr, i-Pr, MeCH(OH), H2N, AcNH) conformed to a multiparameter correla- tion between the logarithms of the concentration ratio of 2- and 3-substituted cations, on the one hand, and substituent constants σI, σR o , and Es o , on the other. The obtained data on the regioselectivity of amination of pyrazines were interpreted in terms of DFT/PBE/3Z quantum-chemical calculations.