4-Toluenesulfonyl chloride → 5-Bromo-3-(5-tert-butyl-1,3,4-oxadiazol-2-yl)pyrazin-2-amine

Participants

Reaction Conditions

Reaction Steps

p-Toluenesulfonyl chloride (164 g, 861.60 mmol) was added portion wise to a suspension of 3-amino-6-bromo-N′-pivaloylpyrazine-2-carbohydrazide (227 g, 718.00 mmol) and N,N-diisopropylethylamine (297 mL, 1795.01 mmol) in acetonitrile (2200 mL). The mixture was stirred for 2 hours at 70° C. The reaction was left to cool to room temperature overnight. The reaction mixture was partitioned between ethyl acetate (2 L) and sodium bicarbonate solution (2 L). The organic layer was washed with saturated brine, dried with magnesium sulfate, filtered, and concentrated under reduced pressure. The resulting brown/beige solid was triturated with hot MTBE (1000 mL) and isolated by filtration and dried to afford 5-bromo-3-(5-tert-butyl-1,3,4-oxadiazol-2-yl)pyrazin-2-amine as a yellow solid (187 g, 87%). The mother liquors were evaporated to dryness. The crude solid was triturated with MTBE (500 mL) filtered and washed with 100 mL of MTBE. The resulting solid was air dried overnight to afford a second crop of 5-bromo-3-(5-tert-butyl-1,3,4-oxadiazol-2-yl)pyrazin-2-amine (36 g, 17%): 1H NMR Spectrum: (DMSO-d6) 1.43 (9H, s), 7.70 (2H, s), 8.39 (1H, s); Mass Spectrum [M+H]+=298.

Provenance & Evidence