Sodium Carbonate → 2-Chloro-3-(4-fluorophenyl)pyridine

Beteiligte Stoffe

Reaktionsschritte

2-Chloro-3-(4-fluorophenyl)pyridine was synthesized analogous to the reaction conditions used in the preparation of 5-(2-chloropyridin-3-yl)-1H-indazole by heating the mixture of 4-fluorophenyl boronic acid (3.0 g, 21.4 mmol), 3-bromo-2-chloropyridine (4.9 g, 25.7 mmol), Pd(PPh3)4 (1.6 g, 1.3 mmol) and 2M aq. Na2CO3 (25 mL, 50 mmol) in 1,4-dioxane (125 mL) under argon atmosphere for 12 h. LC/MS indicated three products with MH+ 208, 254 and 268. Upon work-up of the reaction mixture, as discussed in the preparation of 5-(2-chloropyridin-3-yl)-1H-indazole, the crude concentrated was purified by flash silica gel column chromatography [Combiflash® companion System® with RediSep® silica gel column 120 g, 10-50% EtOAC/hexanes eluting solvent gradient upon liquid loading on to column]. Two fractions containing the desired product were identified and concentrated. 2-Chloro-3-(4-fluorophenyl)pyridine was isolated as a crystalline solid (888 mg, 16%) from the fraction containing 2,3-bis(4-fluorophenyl)pyridine by suspending the semi solid fraction mixture in 10% EtOAc/hexanes and filtered. 1H NMR (DMSO-d6): δ 8.41 (dd, 1H, J=1.8 and 4.7 Hz), 7.86 (dd, 1H, J=2.0 and 7.6 Hz), 7.54-7.48 (m, 3H), 7.34-7.31 (m, 2H). 19F NMR (DMSO-d6): δ −114.06 (s). LCMS: rt 7.50 min (A), purity 99%, MS (m/e) 208 (MH+).

Herkunft & Nachweise