Abstract In order to prepare the 2-chloro derivative of oxolinic acid, ethyl 1-ethyl-1, 4-dihydro- 2-hydroxy-6, 7-methylenedioxy-4-oxo-3-quinolinecarboxylate was treated with phosphorus oxychloride. The compound obtained was the 4-chloro-2-oxo-quinoline. The structure was confirmed by 13 C nmr and mass spectral techniques. The 2-halocarbonitrile was obtained by a Sandmeyer reaction but could not be hydrolysed into the acid.