N-methyliminodiacetic acid → 2-(4-(4-Fluorophenethoxy)phenyl)-6-methyl-1,3,6,2-dioxazaborocane-4,8-dione

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A slurry of (4-(4-fluorophenethoxy)phenyl)boronic acid (122 g, 469 mmol) and 2,2′-(methylazanediyl)diacetic acid (76 g, 516 mmol) in anhydrous toluene (500 mL) and DMSO (200 mL) was refluxed for 4 h. Then, cooled, diluted with EtOAc (500 mL), washed with water (5×200 mL), brine (2×100 mL), dried (MgSO4), filtered and concentrated to give light orange foam which was purified by flash chromatography using 5-40% acetone/CH2Cl2 (5% increment per 2-lit) to afford 2-(4-(4-fluorophenethoxy)phenyl)-6-methyl-1,3,6,2-dioxazaborocane-4,8-dione (131.38 g, 354 mmol, 75% yield) as white solid. 1H NMR (500 MHz, CDCl3) δ 7.43 (d, J=8.4 Hz, 2H), 7.28-7.24 (m, 2H), 7.04-6.99 (m, 2H), 6.92 (d, J=8.5 Hz, 2H), 4.17 (t, J=6.9 Hz, 2H), 4.00 (d, J=16.6 Hz, 2H), 3.76 (d, J=16.6 Hz, 2H), 3.08 (t, J=6.8 Hz, 2H), 2.54 (s, 3H). LCMS (M+H)=372.3.

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