4-Chlorophenylboronic acid → 5-Chloro-4-(4-chlorophenyl)-2-fluoropyridine

Participants

Reaction Conditions

Reaction Steps

A suspension of 5-chloro-2-fluoro-4-iodopyridine (2.57 g, 10 mmol), 4-chlorophenylboronic acid (1.72 g, 11 mmol) and Pd(Ph3P)4 (462 mg, 0.4 mmol) in a mixture of 2.0 M aqueous sodium carbonate (6 mL) and toluene (10 mL) was heated at 140° C. in a microwave oven for 30 min. Analysis by HPLC/MS indicated that the reaction was not complete. Additional 4-chlorophenylboronic acid (0.156 g, 1 mmol) was added, followed by Pd(Ph3P)4 (116 mg, 0.1 mmol). The reaction mixture was again heated at 140° C. in a microwave oven for 30 min. After cooling to room temperature, the reaction mixture was diluted with water and extracted with EtOAc (50 mL×3). The combined EtOAc extracts were washed with saturated aqueous NaCl, dried over Na2SO4, filtered and concentrated under reduced pressure. The crude product was purified using a silica gel cartridge (120 g) eluted with a gradient of EtOAc (0-50%) in hexanes to afford 2.6 g of the product (60% pure) as an off-white solid. This was crystallized in EtOAc-hexanes to obtain the pure title compound (0.9 g) as a white solid. HPLC/MS: retention time=3.80 min, [M+H]+=242.0.

Provenance & Evidence