[CH3:1][O:2][C:3]([C:5]1[C:10]([NH2:11])=[N:9][C:8]([CH2:12][CH:13](OC)[O:14][CH3:15])=[CH:7][N:6]=1)=[O:4].CCN(CC)CC.FC(F)(F)S(O[Si](C)(C)C)(=O)=O.C([O-])(O)=O.[Na+]>C(Cl)Cl>[CH3:1][O:2][C:3]([C:5]1[C:10]([NH2:11])=[N:9][C:8]([CH:12]=[CH:13][O:14][CH3:15])=[CH:7][N:6]=1)=[O:4]
To a solution of 3-amino-5-(2,2-dimethoxy-ethyl)-pyrazine-2-carboxylic acid methyl ester (300 mg, 1.244 mmol) and Et3N (1.213 ml, 8.70 mmol) in DCM (10 ml) at −10° C. was added dropwise trimethylsilyl trifluoromethanesulfonate (0.809 ml, 4.48 mmol). The reaction mixture was stirred at room temperature for 100 min. A saturated solution of NaHCO3 was added and the mixture was extracted twice with DCM. The combined organic layers were washed with NH4Cl solution and brine, dried with Na2SO4, filtered and concentrated under reduced pressure to obtain a brown oil (560 mg). The resulting crude material (mixture of E and Z) was directly used in the next step without further purification.
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