Isoamyl Nitrite → 5-Bromo-6-(4-fluoro-phenyl)-pyrazine-2-carboxylic acid methyl ester

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Reaction Steps

To a suspension of 5-amino-6-(4-fluoro-phenyl)-pyrazine-2-carboxylic acid methyl ester (1.26 g, 5.10 mmol, 1.0 eq) in dibromomethane (25 ml) was added isoamyl nitrite (0.85 ml, 6.29 mmol, 1.2 eq) at room temperature. The resulting suspension was added over 30 minutes at room temperature to a dibromomethane (5 ml) solution of trimethylbromosilane (0.82 ml, 5.90 mmol, 1.15 eq). The mixture was stirred for 2 hours at room temperature after which time the turbid solution was added to aqueous sodium bicarbonate (10%, 15 ml). The phases were mixed, separated and the organic layer dried over magnesium sulfate, concentrated in vacuo and purified by chromatography on silica gel using a gradient of heptane to 10% ethyl acetate in heptane to afford 5-Bromo-6-(4-fluoro-phenyl)-pyrazine-2-carboxylic acid methyl ester as white crystals. Yield=0.81 g (51%). 1H NMR (250 MHz, DMSO): δ 3.92 (3H, s), 7.38 (2H, t, J=8.98 Hz), 7.76-7.81 (2H, m), 8.98 (1H, s). HPLC-MS=100%; 2.13 min (MW=311; M+1=313.0).

Provenance & Evidence