Reaction #1375

Reaction equation

ethyl 1-cyclopropyl-6,7-difluoro-5-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate

hydrochloric acid

→

1-cyclopropyl-6,7-difluoro-5-methyl-1,4,-dihydro-4-oxoquinoline-3-carboxylic acid

Yield 92.7%

Solvents

acetic acid

Conditions

Workup

1. 1
   Temperaturethe mixture is refluxed for 2 hours
2. 2
   TemperatureAfter cooling
3. 3
   Otherthe precipitated crystals are isolated
4. 4
   Washwashed with water, ethanol, and diethyl ether in this order

Procedure

To ethyl 1-cyclopropyl-6,7-difluoro-5-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate (1.9 g) are added 90% acetic acid (20 ml) and conc. hydrochloric acid (5 ml) and the mixture is refluxed for 2 hours. After cooling, the precipitated crystals are isolated, washed with water, ethanol, and diethyl ether in this order to give 1-cyclopropyl-6,7-difluoro-5-methyl-1,4,-dihydro-4-oxoquinoline-3-carboxylic acid (1.6 g), as colorless needles, m.p. 294°-298° C.

Source