Water → Dimethyl 4,7-dimethylpyrazolo[1,5-a]pyrazine-2,3-dicarboxylate

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Reaction Steps

To a solution of 1-amino-2,5-dimethylpyrazin-1-ium-2,4,6-trimethylbenzenesulfonate (4.72 g, 14.6 mmol) in N,N-dimethylformamide (DMF) (50 mL) was added potassium carbonate (4.44 g, 32.1 mmol). The mixture was stirred at room temperature for 10 min. Then a solution of dimethyl but-2-ynedioate (1.87 g, 13.2 mmol) in DMF (30 mL) was added. The resulting mixture was stirred at room temperature for 1 h. Then the mixture was poured into water (400 mL), extracted with EtOAc (3×200 mL). The combined organic layer was dried over sodium sulfate, filtered, evaporated, and chromatographed on silica gel using 20% ethyl acetate (EtOAc) in petroleum ether (PE) as eluent to give 1.04 g (27% yield) of the title compound as a yellow solid. ESI MS: m/z 124.1 [M+H]+. 1H NMR (400 MHz, CDCl3) δ 7.82 (d, J=0.8 Hz, 1H), 4.03 (s, 3H), 4.00 (s, 3H), 2.81 (s, 3H), 2.75 (s, 3H).

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