(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

HRID 49035Notes

Reaction equation

C([N:11]1[CH2:16][CH2:15][N:14]([C:17]2[CH:22]=[C:21]([Cl:23])[C:20]([Cl:24])=[CH:19][C:18]=2[N+:25]([O-])=O)[C@@H:13]([C:28]([OH:30])=O)[CH2:12]1)(OCC1C=CC=CC=1)=O>C(O)(=O)C.[Fe]>[Cl:24][C:20]1[CH:19]=[C:18]2[C:17](=[CH:22][C:21]=1[Cl:23])[N:14]1[CH2:15][CH2:16][NH:11][CH2:12][C@@H:13]1[C:28](=[O:30])[NH:25]2

Participants

Conditions

Temperature: 60 °C

Procedure

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.

Workup

concentrationby concentrated under reduced pressure (1-2 mm, <40° C.) to a gray-black residue
filtrationfiltered
washThe combined ethyl acetate filtrates are washed with 150 mL of 1 N HCl, 200 mL of water (2×), 200 mL of brine
dry with materialdried over MgSO4
filtrationFiltration and concentration of the solvent
customgave a semi-solid material that
customis crystallized from ethyl acetate-hexane

Sources & evidence

ORD record: ord-51600ea0a7ea4754b6da18972bf3c5b2
Source dataset: uspto-grants-2004_03
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06706714B2

Reaction notes

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