5,6-Dichloropyridine-3-carbaldehyde → 2,3-Dichloro-5-ethenylpyridine

Participants

Reaction Conditions

Reaction Steps

To a cooled 0° C., stirred slurry of methyltriphenylphosphonium bromide (10.0 g) in toluene (200 mL) was added potassium t-butoxide (3.07 g) portionwise to produce a yellow slurry. After 1 hr, the reaction mixture was cooled to −20° C. and 2,3-dichloro-5-formylpyridine (2, 4.0 grams, 22.72 mMol) which dissolved in tetrahydrofuran (6 mL) was added dropwise to produce a purple colored slurry. The reaction mixture was warmed to 0° C. and stirred for additional 1 hr. Then the reaction mixture was treated with saturated aqueous brine (150 mL) and diluted with ethyl acetate (200 mL). The resulting organic layer was washed with brine, dried over anhydrous sodium sulfate and concentrated in vacuo. The crude product was purified by silica gel chromatography column eluting with a gradient of ethyl acetate (0-10%)/hexanes to afford 2.77 g of the desired product 3 (70%). 1H NMR (400 MHz, CDCl3) δ 8.30 (1H, d, J=2.19 Hz), 7.80 (1H, d, J=2.19 Hz), 6.63 (1H, dd, J=10.96, 17.80 Hz), 5.86 (1H, d, J=17.80 Hz), 5.45 (1H, d, J=10.96 Hz). LC/MS (M+1): 174.

Provenance & Evidence