p-Toluenesulfonic acid → 2,3-Dichloro-5-ethenylpyridine

Participants

Reaction Conditions

Reaction Steps

To a solution of 1-(5,6-dichloro-pyridin-3-yl)-ethanol 9 (311 g. 1.62 mole) in chlorobenzene (3 L) was added p-toluene sulfonic acid (431 g, 2.5 mole) and the reaction mixture was heated at reflux (about 140° C.) with concomitant removal of water. When the reaction was complete, the mixture was concentrated to about 500 mL, diluted with 2 L water, and extracted with three times (1 L per extraction) ethyl acetate. The organic portions were combined, dried (Na2SO4), concentrated under reduced pressure with low heat, dissolved in 500 mL methylene chloride, and applied to the top of 2 kg silica column. The purified vinyl pyridine was eluted with a 0% to 10% gradient of ethyl acetate in hexane. 178.55 g, of about 100% pure 2,3-dichloro-5-vinylpyridine was collected as a clear oil which solidified upon cooling to 4° C. (63% yield). 1H NMR (400 MHz, CDCl3) δ 8.27 (m, 1H), 7.80 (dd, J=12, 18 Hz, 1H), 6.62 (d, J=18 Hz, 1H), 5.46 (d, J=12 Hz, 1H).

Provenance & Evidence