Ethyl cyanoformate → 4-Chloro-5-[7-(1-ethyl-propyl)-2,5-dimethyl-pyrazolo[1,5-a]pyrimidin-3-yl]-thiophene-2-carboxylic acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

Chill to 0° C. a mixture of 3-(5-bromo-3-chloro-thiophene-2-yl)-7-(1-ethyl-propyl)-2,5-dimethylpyrazolo[1,5-a]pyrimidine (0.62 g, 1.5 mmol) in anhydrous THF (5 mL) under an inert atmosphere and add ethyl magnesium chloride (2 M THF solution, 0.83 mL, 1.65 mmol). Stir the reaction 5 min, warm to room temperature, and stir an additional 15 min before lowering the reaction temperature to 0° C. Add ethylcyanoformate (0.16 mL, 1.58 mmol) diluted in anhydrous THF (1 mL). Warm the reaction to room temperature and stir 1 h. Quench the reaction with saturated sodium bicarbonate (20 mL) and extract with ether (2×75 mL). Combine the organic portions, dry over anhydrous magnesium sulfate, filter, and concentrate under reduced pressure. Purify using flash chromatography, eluting with 100% hexane/0% (20% ethyl acetate/hexane) to 0% hexane/100% (20% ethyl acetate/hexane) in a step gradient of 10% increments. Dry the resulting material under vacuum to provide a white solid (0.114 g, 19%). ES/MS m/z (35Cl) 406.3 (M+1)+.

Provenance & Evidence