C=O.[F:3][C:4]([F:13])([F:12])[C:5]1[CH:10]=[CH:9][C:8]([OH:11])=[CH:7][CH:6]=1.C1(B(O)O)C=CC=CC=1.[C:23](O)(=[O:26])CC.OO>C1C=CC=CC=1.C1COCC1.O>[OH:11][C:8]1[CH:7]=[CH:6][C:5]([C:4]([F:12])([F:13])[F:3])=[CH:10][C:9]=1[CH2:23][OH:26]
Paraformaldehyde (3.4 g, 0.114 mol) was added in 0.5 g portions over a six hour period to a refluxing mixture of 4-trifluoromethyl phenol (2.3 g, 0.0142 mol), phenyl boronic acid (2.1 g, 0.017 mol) and proprionic acid (530 μL, 7 mmol) in benzene with the azeotropic removal of water (Dean-Stark trap). When the addition was complete, the reaction was heated for an additional hour, then cooled with an ice bath, diluted with THF (30 mL) and treated with 5 mL of 30% hydrogen peroxide solution. After stirring for one hour, the mixture was partitioned between water (50 mL) and ethyl acetate (50 mL). The organic layer was washed with NaHSO3 solution (1×50 mL), brine (1×50 mL), dried (Na2SO4), filtered and concentrated. The residue was purified by flash chromatography (30% ethyl acetate/hexanes) to afford 950 mg (35%) of the title compound as a colorless solid. 1H NMR (400 MHz, CDCl3) δ 7.42 (d, 1H, J=9.1 Hz); 7.3 (s, 1H); 6.95 (d, 1H, J=9.1 Hz); 4.89 (s, 2H);
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