(B) In a three-necked reaction flask equipped with a stirrer, propionitrile (4 mol), catalyst (0.1 mol containing 0.05 mol of C-9 cinchona alkaloid-derived primary amine and 0.05 mol of copper complex), benzoic acid (0.1 mol), and N,N-dimethylacetamide (DMA, 0.5 L) were added sequentially. The reaction mixture was cooled to -10 °C with continuous stirring. Subsequently, N,N-dimethylacetamide solution (0.3 L) containing 1-(2,5-difluorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethanone (1 mol) was slowly added dropwise, keeping the reaction temperature at -10 °C. The progress of the reaction was monitored by thin layer chromatography (TLC) until the reaction was complete. Upon completion of the reaction, the reaction was quenched by the addition of hydrochloric acid solution (1 mol / 0.3 L) and then extracted with ethyl acetate (0.2 L x 3). The organic phases were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to give an oil. The oily substance was treated with a solvent mixture of n-heptane/dichloromethane (1:1, v/v), and after recrystallization, filtration and drying, (2S,3R)-3-(2,5-difluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4-triazol-1-yl)butanenitrile was obtained in off-white solid form in a yield of 80%, with an diastereoisomer ratio (dr) of 97:3.
