4-Bromodiphenyl Ether → 4-Phenoxyphenylboronic acid

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To a solution of 4-phenoxybromobenzene (98.2 g, 0.39 mol) in dry THF (800 mL) under nitrogen at −78° C. was added n-BuLi (2.5M solution in hexanes) (172 mL, 0.43 mol) dropwise. A temperature rise to −65° C. was observed. On complete addition, the mixture was allowed to stir at −78° C. for 15 min. Triisopropylborate (109.2 mL, 0.473 mol) was added dropwise over 30 min. On complete addition, a suspension was observed. The mixture was allowed to warm to 0° C. over 1 hr, stirred at 0° C. for 4 hrs. The reaction was quenched by the dropwise addition of water (300 mL) such that the internal temperature<20° C. (ice-cooling required). The mixture was allowed to warm to room temperature overnight then evaporated to dryness. The residue was suspended in water (600 mL) and acidified by the cautious addition of conc. HCl. The resulting precipitate was collected by filtration and dried in vacuo at 45° C. The solid was ground to a fine powder and triturated with petroleum ether (40-60° C.). The pale solid was filtered and dried to give 4-phenoxyphenylboronic acid (68.8 g, 83%). 1H NMR (250 MHz, d6-DMSO):7.99 (1H, m), 7.91 (1H, t), 7.83 (1H, d), 7.4 (2H, m), 7.14 (1H, m), 6.92-7.07 (5H, m). Microanalysis:Req. C(71.4%), H(5.45%), Found C(70.25%), H(4.7%).

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