Dimethyl Sulfoxide → 8-Chloro-1-(4-oxo-cyclohexyl)-4H,6H-2,3,5,10b-tetraaza-benzo[e]azulene-5-carboxylic acid tert-butyl ester

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Reaction Conditions

Reaction Steps

To a solution of oxalyl chloride (0.11 ml, 1.3 mmol) in dichloromethane (8 ml) was added dimethylsulfoxide (0.21 ml, 2.6 mmol) at −60° C. The mixture was stirred for 5 minutes at −50° C. A solution of cis/trans-8-chloro-1-(4-hydroxy-cyclohexyl)-4H,6H-2,3,5,10b-tetraaza-benzo[e]azulene-5-carboxylic acid tert-butyl ester (0.046 g, 1.1 mmol) in dichloromethane (3 ml) was added at −65° C. Stirring for 30 minutes was followed by addition of triethylamine (0.77 ml, 5.5 mmol). The cooling bath was removed after 5 minutes, and the reaction mixture was stirred for 1 h. The reaction mixture was washed with one portion of aqueous saturated ammonium chloride solution. The aqueous layer was extracted with three portions of tert-butyl methyl ether. The combined organic layers were dried over anhydrous sodium sulfate and concentrated in vacuo. Flash-chromatography with n-heptane/ethyl acetate as eluent gave the title compound (0.41 g, 90%) as white solid. MS m/e: 417 (M+H+)

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