Ethanol → 2-(4-{2-[2-(4'-Formylbiphenyl-3-yl)-5-methyloxazol-4-yl]ethoxy}phenoxy)-2-methyl propionic acid ethyl ester

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A solution of 2-(4-{2-[2-(3-bromophenyl)-5-methyloxazol-4-yl]ethoxy}phenoxy)-2-methylpropionic acid ethyl ester (0.907 mmol) (see Ex. 3, part F) and 1-(4-formylphenyl)boronic acid (0.998 mmol) in toluene:ethanol (18.2 mL of a 1:1 solution) was treated with Na2CO3(aq) (0.906 mL of a 2M solution). A nitrogen atmosphere was applied, Pd(PPh3)4 (0.045 mmol) was added, and the orange mixture was heated at reflux for 2 h. After cooling to room temperature, the mixture was partitioned between ethyl acetate (20 mL) and H2O (30 mL). The layers were separated, and the aqueous phase was back-extracted with ethyl acetate (2×10 mL). Combined organic phases were washed with brine (20 mL), dried over Na2SO4, and concentrated. The product was purified by silica gel chromatography (20 g SiO2, 3:7 ethyl acetate:hexanes). Rf=0.24 in 1:4 ethyl acetate:hexanes; 1H NMR (400 MHz, CDCl3) δ 10.03 (s, 1H), 9.21 (s, 1H), 9.02-8.94 (m, 3H), 8.81-8.78 (m, 2H), 8.46-8.41 (m, 1H), 8.36-8.30 (m, 1H), 6.79-6.71 (m, 4H), 4.23-4.16 (m, 4H), 2.94 (t, 2H), 2.37 (s, 3H), 1.26 (s, 6H), 1.24 (t, 3H); MS (EI) 514.2 (M+H)+.

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