Trimethyl borate → [4-(Morpholine-4-carbonyl)phenyl]boronic acid

Participants

Reaction Steps

Isopropylmagnesium chloride (27.8 mL, 2 M in THF, 55.6 mmol) was added to a solution of bis(2-dimethylaminoethyl)ether (10.5 mL, 55.6 mmol) in THF (230 mL) 15° C. After 20 minutes, (4-iodophenyl)-(morpholino)methanone (14.7 g, 46.4 mmol) was added and the reaction was removed from the cooling bath. After 1 hr, another 0.8 eq of isopropylmagnesium chloride was added. Trimethyl borate (10.6, 93 mmol) was added after 15 minutes, and after stirring 40 min, the reaction was quenched with 150 ml 1 N aqueous HCl. After stirring at room temperature for 2 hr, THF was removed on the rotary evaporator and the residue was extracted three times with EtOAc. The organic extracts were dried with Na2SO4. The solvent was removed and the residue was twice suspended in toluene and the solvent removed on the rotary evaporator. The resulting white solid was suspended in hexane and this was heated at reflux for 5 minutes. After cooling to room temperature, the white solid was collected by filtration and air-dried to afford 4-(morpholine-4-carbonyl)phenylboronic acid (8.7 g). MS (ESI) m/z 236.1 (M+H). 1H NMR (MeOD) δ ppm 7.78 (2H, d, J=7.30 Hz), 7.36 (2H, d, J=8.06 Hz), 3.72-3.41 (8H, m).

Provenance & Evidence