[F:1][C:2]([F:15])([F:14])[C:3]1[CH:8]=[CH:7][C:6](/[CH:9]=[CH:10]/[C:11](=[O:13])[CH3:12])=[CH:5][CH:4]=1.B1(C)OC(C2C=CC=CC=2)(C2C=CC=CC=2)[C@@H]2N1CCC2.[B]1OC2C(=CC=CC=2)O1>C1(C)C=CC=CC=1>[F:1][C:2]([F:14])([F:15])[C:3]1[CH:4]=[CH:5][C:6](/[CH:9]=[CH:10]/[C@@H:11]([OH:13])[CH3:12])=[CH:7][CH:8]=1(E)-4-(4-(trifluoromethyl)phenyl)but-3-en-2-one (15 g, 70 mmol) was taken up in 500 mL of toluene. (R)-2-Methyl-CBS-oxazaborolidine, 1.09 M in toluene (6.4 mL, 7.0 mmol) was added, and the mixture was chilled to −78° C. Catecholborane (13 mL, 119 mmol) was added dropwise via addition funnel in 125 mL of toluene. The mixture was stirred for 25 minutes and then gradually warmed to −45° C. and stirred for 2 hours. The yellow color taken on during the catecholborane addition faded during this time and the solution cleared. The mixture was quenched with 300 mL of water and warmed to room temperature. The mixture was partitioned in a separatory funnel. The organic portion was washed 3 times with 200 mL of 5% aq. KOH (to remove the catechol), twice with 200 mL of 10% aq. HCl (to remove the (R)-2-methyl-CBS-oxazaborolidine catalyst), and once with 200 mL of brine, then dried over MgSO4. Filtration and concentration under reduced pressure afforded (S,E)-4-(4-(trifluoromethyl)phenyl)but-3-en-2-ol (15 g, 99% yield) as a yellow oil that slowly crystallized on the bench top. 1H NMR (400 MHz, CDCl3) δ ppm 7.57 (d, J=8.22 Hz, 2H) 7.50-7.45 (m, 2H) 6.62 (d, J=16.04 Hz, 1H) 6.36 (dd, J=16.04, 6.06 Hz, 1H) 4.49-4.57 (m, 1H) 1.61 (d, J=4.30 Hz, 1H) 1.39 (d, J=6.46 Hz, 3H).
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