2-Chloro-4-ethynylpyridine synthesis

Yield:945717-09-9 91%

Reaction Conditions:

with tetrabutyl ammonium fluoride in tetrahydrofuran at -78 - 0; for 0.75 h;

Steps:

S4.C.b

To a solution of 2.389 g of 2-chloro-4-trimethylsilanylethynyl-pyridine (11.39 mmol) in THF (90 ml) were added 11.39 ml of a 1 M TBAF solution in THF at -78° C. and the reaction mixture was stirred for 45 min at 0° C. Then saturated NH₄Cl solution was added and the THF was removed under reduced pressure. The aqueous mixture was extracted with diethylether and the combined organic extracts were washed with water and brine, dried (Na₂SO₄), filtered and concentrated in vacuo. The remaining residue was purified by column chromatography (pentane/diethylether 100:0 to 4:1) to give 2-chloro-4-ethynyl-pyridine (1.427 g, 91%) as an off-white solid. ¹H-NMR (CDCl₃, 300 MHz: δ 3.36 (s, 1H), 7.27 (dd, J=5 and 1 Hz, 2H), 7.40 (br s, 1H), 8.37 (d, J=8 Hz, 2H).

References:

US2007/185058,2007,A1 Location in patent:Page/Page column 12