Acetic Anhydride → 2-Acetylamino-3,4,5,6-tetrafluorobenzoic acid

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Reaction Steps

The general pathway to the compounds of formula IV is illustrated with 2-nitro-3,4,5,6-tetrafluorobenzoyl chloride. This starting material is treated with n-butyl lithium and malonic half acid ester to form 2-nitro-3,4,5,6-tetrafluoro-β-oxo-benzene propanoic acid ethyl ester. This product can be converted to 5-nitro-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid ethyl ester by a three step reaction. The starting material is first treated with triethylorthoformate and subequently with cyclopropyl amine in t-butyl alochol. The product is ring closed with potassium t-butoxide to form 5-nitro-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid ethyl ester. This product is hydrogenated to form the corresponding 5-amino compound. This is then hydrolyzed to form 1-cyclopropyl-5-amino-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid. Alternatively compounds of the formula IV may be prepared by a series of reactions illustrated with 3,4,5,6-tetrafluoroanthranilic acid. The acid is reacted with acetic anhydride and acetic acid to form 2-acetylamino-3,4,5,6-tetrafluorobenzoic acid. This compound is reacted with oxalyl chloride and dichloromethane in the presence of N,N-dimethylformamide catalyst to form 2-acetylamino-3,4,5,6-tetrafluorobenzoyl chloride. This product is treated with n-butyl lithium and malonic half acid ester to form 2-acetylamino-3,4,5,6-tetrafluoro-β-oxobenzenepropanoic acid ethyl ester.

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