Cesium carbonate → 5-Ethenyl-2-(trifluoromethyl)pyridine

Participants

Reaction Conditions

Reaction Steps

Potassium vinyltrifluoroborate (362 mg, 2.7 mmol; Aldrich), 5-bromo-2-trifluoromethylpyridine (539 mg, 2.38 mmol; Aldrich) and triphenylphosphine (37.7 mg, 0.144 mmol) were added at room temperature to a solution of cesium carbonate (2.16 g, 6.63 mmol) in water (2 mL). Tetrahydrofuran (18 mL) was added, and the reaction flask was evacuated and purged with nitrogen (3 cycles). Palladium(II) chloride (9.2 mg, 0.052 mmol) was added, and the reaction flask was again evacuated and purged with nitrogen (3 cycles), then heated under nitrogen at 75-80° C. for 22 hours. The mixture was cooled to room temperature and the aqueous layer was separated and extracted with ethyl ether (2×5 mL). The combined organic phase was concentrated by distillation through a Vigreaux column at atmospheric pressure to a volume of approximately 2 mL, and the residue was purified by flash chromatography (40 g silica, eluted with hexanes-ethyl acetate, 100:0-90:10). The product-containing fractions were combined and concentrated by distillation through a Vigreaux column at atmospheric pressure to a volume of approximately 2 mL, then distilled bulb-to-bulb (air bath 80-90° C./10-20 torr) to provide the title compound: 1H NMR (300 MHz, methanol-d4) δ 5.56 (d, J=10.9 Hz, 1H), 6.08 (d, J=17.6 Hz, 1H), 6.86 (dd, J=17.8, 11.0 Hz, 1H), 7.77 (d, J=8.1 Hz, 1H), 8.11 (dd, J=8.3, 2.2 Hz, 1H), 8.74 ppm (d, J=1.7 Hz, 1H).

Provenance & Evidence