Triethylamine → {3-[(2,6-Dichlorobenzoyl)oxy]phenyl}boronic acid

To make compound (6a), a solution of 2,6-dichlorobenzoyl chloride (29 μL, 0.2 mmol) in 5 mL of dried THF was added dropwise to an ice-cold solution of 3-hydroxyphenylboronic acid (21 mg, 0.15 mmol), dried triethyl amine (42 μL, 0.3 mmol) and 10 mL of dried THF. The reaction mixture was stirred at room temperature overnight and then evaporated to dryness. It was dissolved in 25 mL of ethyl acetate and washed with 1N aqueous HCl, 10% aqueous NaHCO3, saturated brine solution, dried (Na2SO4) and then concentrated. The residue was purified by flash chromatography eluting with MeOH-ethyl acetate (1:10) to give 38 mg (81% yield) of desired compound as a white powder, mp: 238° C.(dec). 1H-NMR (400 MHz, 5% D2O in d6-DMSO): δ7.08–7.19 [m, 1H, Ar—H], 7.22–7.30 [m, 1H, Ar—H], 7.22–7.30 [m, 1H, Ar—H], 7.42–7.50 [m, 1H, Ar—H], 7.54–7.60 [m, 1H, Ar—H], 7.60–7.68 [m, 2H, Ar—H], 7.73–7.78 [m, 3H, Ar—H].