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

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.

1. customThe crude reaction mixture
2. concentrationwas then concentrated under reduced pressure
3. additiondiluted with about 50 mL of hexanes/ethanol (1:1)
4. customto 0° C.
5. additionconcentrated NH4OH (aq.) was added slowly to the stirring mixture until a pH of 7-8
6. extractionThe mixture was extracted (4×) with hexanes
7. dry with materialthe combined oganic portions were dried (Na2SO4)
8. filtrationfiltered
9. temperatureThe hexanes solution was heated for 10 minutes with activated charcoal
10. filtrationfiltered through 2 inches of silica gel (EtOAc/hexanes eluent)
11. customEvaporation of the solvents under reduced pressure

ORD record

ord-9085a8a031fc445894d838db77984b08

Source dataset

uspto-grants-1994_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05306819