Acetic Anhydride → 6,7,8-Trifluoro-1,4-dihydro-1-(1-methylcyclopropyl)-4-oxo-3-quinolinecarboxylic acid

Participants

Reaction Steps

To 3.0 g (11.33 mmol) of the 2,3,4,5-tetrafluoro-β-oxo-benzenepropanoic acid, ethyl ester was added 2.76 g of acetic anhydride and 2.5 g of triethylorthoformate. These were refluxed for 2.5 hours and concentrated under high vacuum at 80° C. The residual oil was treated at 45° C. with 1.33 g (1.1 equivalents) of 1-amino-1-methylcyclopropane hydrochloride (U.S. Pat. No. 3,451,802) in 50 ml of t-butanol. To this mixture was added 1.43 g (1.1 equivalents) of potassium t-butoxide in 20 ml t-butanol. After 24 hours the mixture was treated with an additional 1.1 equivalents of potassium t-butoxide in 20 ml of t-butanol and was heated to 75° for 24 hours. The reaction was cooled, partially concentrated, and filtered. The solids were dissolved in 75 ml of hot acetic acid and 25 ml of 3 N hydrochloric acid was added in portions over two hours at 100° C. The reaction was maintained at this temperature for two additional hours and 20 ml of water was added. The mixture was cooled and filtered to give 2.0 g of 6,7,8-trifluoro-1,4-dihydro-1-(1-methylcyclopropyl)-4-oxo-3-quinolinecarboxylic acid, mp 292°-294° C.

Provenance & Evidence