2-Aryl-quinoline-4-carboxylic acid (3, 10 mmol) was suspended in SOCl2 (12 mmol) at 0 °C. The mixture was refluxed for 2 h and cooled to 0 °C. Methanol (5 mL) was added to get the hydrochloride salt of the methyl ester derivative. Cold water (15 mL) was added to the mixture and its pH was adjusted to 7.0 with saturated with aqueous NaHCO3 solution. The precipitated solid was filtered, washed with cold water (2 × 10 mL), and dried under reduced pressure to get 2-(phenyl derivates)-quinoline-4-carboxylic acid methyl ester.
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