(R)-4-carbobenzyloxy-1-(4,5-dichloro-2-nitrophenyl)-piperazine-2-carboxylic acid → (R)-8,9-Dichloro-2,3,4,4a-Tetrahydro-1H-Pyrazino[1,2-a]Quinoxalin-5(6H)-One

Participants

Reaction Conditions

Reaction Steps

To a solution of 8.0 g (R)-4-carbobenzyloxy-1-(4,5-dichloro-2-nitrophenyl)-piperazine-2-carboxylic acid in 200 mL of acetic acid is added 6.0 g of iron powder. With good stirring, the mixture is heated at 60° C. for 2 hours, followed by concentrated under reduced pressure (1-2 mm, <40° C.) to a gray-black residue. This material was slurried with 400 mL of ethyl acetate and filtered. This process was repeated. The combined ethyl acetate filtrates are washed with 150 mL of 1 N HCl, 200 mL of water (2×), 200 mL of brine and dried over MgSO4. Filtration and concentration of the solvent gave a semi-solid material that is crystallized from ethyl acetate-hexane to afford 5.44 g (76.1%) of title compound as a white solid, mp 136-138° C.

Provenance & Evidence