5-Bromo-6-(3-chloro-phenyl)-pyrazine-2-carboxylic acid (0.200 g, 638 μmol) was suspended in dichloromethane (1 mL) and 1-chloro-N,N,2-trimethylpropenylamine (98.0 mg, 97.0 μl, 734 μmol) was added dropwise at room temperature. After 30 min stirring the brown solution was added drop by drop to a solution of α,α,5-trimethyl-1,2,4-oxadiazole-3-methanamine hydrochloride (CAN 1240526-27-5; 142 mg, 797 μmol) and ethyldiisopropylamine (206 mg, 264 μl, 1.59 mmol) in DMF (1 mL) and the reaction mixture was stirred at room temperature for 30 minutes. The mixture was extracted with ethyl acetate and 1M citric acid solution; the organic phase was dried with MgSO4; filtered and concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, 20 g, 5% to 50% ethyl acetate in n-heptane) to give the desired product (126 mg, 45%) as white foam; MS (EI): 436.0 (M+H).
