Diisopropylamine → 2-Chloro-3-pyridinecarboxaldehyde

Participants

Reaction Conditions

Reaction Steps

THF (200 mL) in a dry flask under N2 is chilled by placing the flask in a dry-ice/acetone bath at −78° C. Butyllithium (125 mL, 200 mmol) is added drop-wise, followed by the drop-wise addition of iodobenzene (11.19 mL, 100 mmol) in THF (10 mL). The solution is allowed to stir for 30 min at −78° C. Diisopropylamine (0.70 mL, 5 mmol) in THF (3 mL) and 2-chloropyridine (9.46 mL, 100 mmol) in THF (30 mL) are added successively in a drop-wise manner, and the solution is stirred for 1 h at −40° C. Formyl piperidine (11.1 mL, 100 mmol) in THF (25 mL) is added drop-wise, and the solution is stirred for 1 h at −40° C. The reaction is quenched with 40 mL 6N HCl, diluted with 250 mL ether, and a small amount of sodium thiosulfate solution is added to remove the iodine color. The solution is neutralized with saturated NaHCO3, filtered, and extracted with ether (3×150 mL). The combined organic layer is dried over Na2SO4, filtered, and concentrated in vacuo. The crude material is chromatographed over 600 g slurry-packed silica, eluting with 20% EtOAc/hexane. The fractions with the desired compound are collected and concentrated to afford 2-chloronicotinaldehyde (C90) as a pale orange solid (54% yield). MS (EI) for C6H4ClNO, m/z: 141 (M)+.

Provenance & Evidence