Calcium Chloride → 4,5-Dichloropyridine-2,3-diamine

Participants

Reaction Steps

2-Amino-4,5-dichloro-3-nitropyridine (Example 206b) (1.04 g, 5.0 mmol), zinc powder (2.4 g, 37 mmol) and anhydrous calcium chloride (3 g, 27 mmol) were mixed in 95% ethanol (30 ml) and heated to reflux for 1 h. When cool, the reaction mixture was filtered through celite and evaporated in vacuo. The residue was dissolved in methanol/dichloromethane 1:1 and chromatographed through a short column of silica (10 g) eluting with methanol/dichloromethane 3:7. The fraction containing the product was concentrated in vacuo and the residue dissolved in methanol/acetonitrile 1:9 and again concentrated in vacuo together with silica. The product thus adsorbed on silica gel was again subjected to chromatography on silica gel (EtOAc) to afford the pure product as a off-white powder (0.60 g, 67%).

Provenance & Evidence