Pyrazine N-oxides are widely used in the fields of organic synthesis,biomedicine,and ener-getic materials.The traditional synthesis method mainly involves the hydrogen peroxide/acetic acid oxi-dation system,which can cause the environmental pollution and also limit the use of acid sensitive sub-strates.Therefore,it is urgent to develop a green method for the synthesis of pyrazine N-oxides.In this study,using 2,5-dimethylpyrazine as a template substrate,the optimal reaction conditions were ob-tained by screening the ratio of raw materials,bases,and solvents.Methanol was used as the reaction solvent,and the ratio of substrate,H2O2 and NaHCO3 to each other was 1.0∶1.2∶3.6.Under the promotion of F2O2S,the reaction occurred at room temperature for 50 minutes.Eleven corresponding pyrazine N-oxides 2a～2k were obtained with yields ranging from 10％～84％.Their structures were confirmed by 1H NMR,13C NMR and MS(ESI).The two nitrogen atoms of 2,6-dimethoxy-pyrazine are in different chemical environments.By confirming the selectivity of the nitrogen oxidation reaction,compound 2f was characterized by single crystal X-ray diffraction,and it was determined that the oxi-dation reaction preferentially occurred at the 4-position N atom with low site-resistance.This reaction can be carried out under weakly alkaline conditions,avoiding the use of acids and conforming to the concept of green chemistry.
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