Phosphorus oxychloride → 2-Chloro-5,6,7,8-tetrahydroquinoxaline

Participants

Reaction Steps

A solution of 5,6,7,8-tetrahydroquinoxalin-2-one (1.01 g, 0.0067 mol) in excess POCl3 (20 mL) was refluxed for 19 h under an atmosphere of dry nitrogen. The crude reaction mixture was then concentrated under reduced pressure and diluted with about 50 mL of hexanes/ethanol (1:1). After bringing the solution to 0° C., concentrated NH4OH (aq.) was added slowly to the stirring mixture until a pH of 7-8 was attained. The mixture was extracted (4×) with hexanes, and the combined oganic portions were dried (Na2SO4) and filtered. The hexanes solution was heated for 10 minutes with activated charcoal and filtered through 2 inches of silica gel (EtOAc/hexanes eluent). Evaporation of the solvents under reduced pressure yielded 2-chloro-5,6,7,8-tetrahydroquinoxaline as a pale yellow oil.

Provenance & Evidence