Pivalic acid → 3-(5-Tert-butyl-1,3,4-oxadiazol-2-yl)pyrazin-2-amine

Participants

Reaction Conditions

Reaction Steps

2-(1H-benzo[d][1,2,3]triazol-1-yl)-1,1,3,3-tetramethylisouronium tetrafluoroborate (47.7 g, 148.69 mmol) was added portionwise over 15 minutes to a stirred suspension of N-ethyl-N-isopropylpropan-2-amine (70.6 mL, 405.51 mmol), pivalic acid (17.08 mL, 148.69 mmol) and 3-aminopyrazine-2-carbohydrazide (20.7 g, 135.17 mmol) in acetonitrile (350 mL) and the reaction mixture was stirred at 80° C. for 20 minutes (a solution was obtained). The reaction mixture was cooled to 0° C. and N-ethyl-N-isopropylpropan-2-amine (70.6 mL, 405.51 mmol), followed by 4-methylbenzene-1-sulfonyl chloride (77 g, 405.51 mmol) were added over a period of 15 minutes. The reaction mixture (yellow suspension) was brought to reflux (solubilisation) and then allowed to stir at room temperature for 14 hours affording a dark orange solution. The solution was concentrated. The residue was diluted with dichloromethane, washed with water, brine, dried over magnesium sulfate and concentrated. The crude product was purified by flash chromatography on silica gel eluting with 0 to 40% ethyl acetate in dichloromethane. The solvent was evaporated to dryness. The resulting mixture was triturated with ether (100 mL), filtered, washed with the minimum of ether and dried to afford 3-(5-tert-butyl-1,3,4-oxadiazol-2-yl)pyrazin-2-amine (20.8 g, 70.2%) as a pale yellow soild: 1H NMR Spectrum; (CDCl3) 1.53 (9H, s), 1.58-1.68 (2H, m), 6.67 (2H, s), 8.13 (2H, dt); Mass Spectrum [M+H]+=220.

Provenance & Evidence