1,3-Cyclohexanedione → 9-[5-(5,6-dichloro-1H-benzimidazol-2-ylsulfanyl)-furan-2-yl]-8-oxo-4,5,6,7,8,9-hexahydro-2H-pyrrolo[3,4-b]quinoline-3-carboxylic acid ethyl ester

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Reaction Steps

A suspension of 231.3 mg (1.5 mmol) of 3-amino-2-ethoxycarbonylpyrrole and 469.7 mg (1.5 mmol) of 5-(5,6-dichloro-1H-benzimidazol-2-ylsulfanyl)-furan-2-carbaldehyde (obtained from step 1) in 7.5 mL of n-butanol under argon is stirred at room temperature until complete dissolution. 1,3-Cyclohexanedione (168.2 mg, 1.5 mmol) is then added and the reaction mixture is heated at reflux temperature for 1.5 h. The mixture is then cooled to room temperature and concentrated under reduced pressure. The residue is purified by chromatography on a prepacked 90 g 15-40 μm silica gel cartridge (eluting solvent: dichloromethane/methanol 100/0 to 90/10 v/v; rate: 40 mL/min). The fractions containing the desired product are combined and concentrated to dryness under reduced pressure. The residue is recrystallized from ethanol and the solid is filtered, washed with ethanol and dried under reduced pressure. 431 mg of 9-[5-(5,6-dichloro-1H-benzimidazol-2-ylsulfanyl)-furan-2-yl]-8-oxo-4,5,6,7,8,9-hexahydro-2H-pyrrolo[3,4-b]quinoline-3-carboxylic acid ethyl ester are obtained as a beige crystalline powder. mp: 180° C. LCMS: m/z 543: [M+H]+ (base peak). EA.

Provenance & Evidence