2.4. Preparation of 3-Pyridin-4-yl-4,4′-Difluorobenzophenone (4)

Compound (3) (25 mg, 0.084 mmol), 4-pyridylboronic acid (15.5 mg, 0.126 mmol), tetrakis(triphenylphosphine)palladium(0) (10 mg, 0.008 mmol) and potassium carbonate (50 mg, 0.36 mmol) in dimethylformamide (3.5 mL) and water (0.5 mL) were mixed together under inert conditions. The reaction was heated to 160 °C for 10 min using microwave irradiation. The reaction solution was concentrated to dryness and the residue was taken up in water and was two times extracted with ethyl acetate. Then, the organic extracts were combined, dried over magnesium sulfate and evaporated. Finally, the crude product was purified by silica gel chromatography (ethyl acetate/hexane (1/1), then pure ethyl acetate) to give compound (4): 18 mg (73%). ¹H-NMR (300 MHz, CD₂Cl₂) δ 7.25–7.17 (m, 2H) 7.36–7.30 (dd, J = 8.6, 10.2 Hz, 1H) 7.52–7.49 (dd, J = 1.6, 4.4 Hz, 2H) 7.88–7.81 (m, 3H) 7.96–7.93 (dd, J = 2.2, 7.3 Hz, 1H) 8.69–8.67 (dd, J = 1.6, 4.4 Hz, 2H). ¹³C-NMR (75 MHz, CD₂Cl₂): δ 116, 117, 124, 127.1, 127.3, 133, 134, 135, 142, 151, 161, 164, 168. IR ν = 3057 (w), 1653 (s), 1590 (s), 1502 (m), 1400 (m), 1306 (m), 1223 (s), 1129 (m), 1042 (w), 993 (w), 858 (m), 763 (s), 694 (m), 585 (s). MS(ESI): m/z 296.09 [(M + H)⁺, calcd 296.09].