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General procedure for the synthesis of 4-chloroquinoline-7-carboxylic acid from 4-chloro-7-trifluoromethylquinoline: 10.0 g (43.2 mmol) of 4-chloro-7-trifluoromethylquinoline was dissolved in 200 mL of concentrated hydrochloric acid. The reaction was heated in a microwave reactor with radiation at 550 W power for 2 hours. Upon completion of the reaction, the reaction mixture was slowly poured into ice water and the pH was adjusted to 3-4 with sodium hydroxide solution.The precipitated product was collected by diafiltration, washed several times with deionized water and subsequently dried. Finally 8.9 g of 4-chloroquinoline-7-carboxylic acid was obtained in 99% yield of the theoretical value. Thin layer chromatography (TLC) analysis showed an Rf value of 0.45 (silica gel plate, unfolding agent was toluene/ethanol = 4:1). The molecular formula of the product was C10H6ClNO2 (molecular weight 207.62), and the mass spectrometry analysis showed that the molecular ion peak (M+H)+ was 208/210 (chlorine isotope peak).

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