Abstract: A new catalytic system was applied to the oxidation reactions involved in the synthesis of 2,6-diamino-3,5-dinitropyrazine-1-oxide(LLM-105), in which protonated peroxotungstate immobilized into the network of cross-linked chitosan with the superparamagnetic Fe3O4 core(Fe3O4/CS/HWO) was used as the catalyst. With H2O2 as the oxidant, good to excellent yields could be achieved with pyrazine, 2,6-dimethoxypyrazine, 2,6-dichloropyrazine and 2-chloro-6-methoxypyrazine as the substrates without addition of trifluoracetic acid. A representative procedure for the oxidation process is as following: to 30 mL of CH3CN containing substrate(10 mmol) and Fe3O4/CS/HWO(0.1 mmol, about 0.1 g), 30%H2O2(5 mL) was added dropwisely by 5 times at 60 ℃ temperature. The oxidation process was monitored by TLC. Product could be obtained with a yield ranging from 60% to 73%. Theoretical studies were also carried out with Gaussian 03 to evaluate the oxidation process. All of the calculated data matched well with the experimental results.

Key words: protonated peroxotungstate, oxidation, pyrazine derivatives, diamino-dinitropyrazine-oxide, theoretical studies