Cesium carbonate → 2-(4-{2-[2-(4-Bromophenyl)-5-methyloxazol-4-yl]ethoxy}phenoxy)-2-methylpropionic acid ethyl ester

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A mixture of toluene-4-sulfonic acid 2-[2-(4-bromophenyl)-5-methyloxazol-4-yl]ethyl ester, 2-(4-hydroxyphenoxy)-2-methylpropanoic acid ethyl ester (American Home Products U.S. Pat. No. 3,795,691) (7.06 g, 31.5 mmol) and Cs2CO3 (13.3 g, 41.0 mmol) was heated at 55° C. in DMF (45 mL) for 18 h. The reaction was partitioned between ethyl acetate (250 mL) and H2O (250 mL), and the aqueous phase extracted with ethyl acetate (2×100 mL). The combined organic phases were dried (MgSO4) and concentrated under reduced pressure to an oil which was purified by column chromatography (1500 mL SiO2, hexanes to 10% ethyl acetate/hexanes) to provide 2-(4-{2-[2-(4-bromophenyl)-5-methyloxazol-4-yl]ethoxy}phenoxy)-2-methyl propionic acid ethyl ester (6.81 g, 44%) as a off-white solid: Rf-=0.48 in 35% ethyl acetate/hexanes; mp 78-79° C.; 1H NMR (300 MHz, CDCl3) δ7.85-7.82 (m, 2H), 7.57-7.53 (m, 2H), 6.83-6.75 (m, 4H), 4.22 (q, J=7.0 Hz, 2H), 4.18 (t, J=6.6 Hz, 2H), 2.94 (t, J=6.7 Hz, 2H), 2.36 (s, 3H), 1.52 (s, 6H), 1.27 (t, J=7.0 Hz, 3H) and by-product 2-(4-Bromophenyl)-5-methyl-4-vinyloxazole (1.81 g, 22%) as a white solid:

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