[C:1]1([C:7]2[C:11]([C:12]([F:15])([F:14])[F:13])=[C:10]([C:16](O)=[O:17])[O:9][N:8]=2)[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.CN1CCOCC1.ClC(OCC(C)C)=O.[BH4-].[Na+]>C1COCC1.CO>[C:1]1([C:7]2[C:11]([C:12]([F:15])([F:13])[F:14])=[C:10]([CH2:16][OH:17])[O:9][N:8]=2)[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=1To 3-phenyl-4-(trifluoromethyl)isoxazole-5-carboxylic acid (Intermediate I-3D, 1 g, 3.89 mmol) in THF (10 mL), cooled to −10° C., was added N-methylmorpholine (0.470 mL, 4.28 mmol) followed by isobutyl chloroformate (0.562 mL, 4.28 mmol) over a period of 3 min. After 15 min. at −10° C., this heterogeneous reaction mixture was added to a suspension of sodium borohydride (0.191 g, 5.06 mmol) in THF (12 mL) and methanol (3.0 mL) at −78° C. over a period of 10 min. using a Pasteur pipette. The reaction mixture was stirred at −78° C. for 10 min. The reaction mixture was allowed to warm to −20° C. over a period of 30 min. and quenched by the slow addition of AcOH in water (1:9 mL). The reaction mixture was allowed to come to room temperature, concentrated under reduced pressure and the residue partitioned between ethyl acetate (60 mL) and water (10 mL). The ethyl acetate layer was separated and washed sequentially with sat. aq. sodium bicarbonate (10 mL), brine (10 mL), dried over sodium sulfate and concentrated. The resulting oil was subjected to silica gel column chromatography using hexane/ethyl acetate to yield (3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)methanol (0.44 g, 1.809 mmol, 46.5% yield) as an oil. 1H NMR (500 MHz, CDCl3) δ ppm 2.21 (br. s., 1H), 4.97 (s, 2H), 7.47-7.56 (m, 3H), and 7.65 (d, J=6.60 Hz, 2H); LCMS M+1=244.
読み込み中…
