Anthranillic acid (1 g, 7.3 mmol, 1.0 eq) was dissolved in dry benzene (20 ml)  in a round bottomed flask and thionyl chloride (0.6 ml, 5.2 mmol) was added dropwise to the anthranillic acid under an inert atmosphere. The mixture was refluxed for 30 minutes at ambient temperature. This led to the formation of iminoketene (6-iminocyclohexa-2,4 dienylidene) methanone. Diethyl malonate 1.2 ml (1.1 mmol) was then added to the round bottom flask. The iminoketene (6-iminocyclohexa-2,4 dienylidene)methanone formed reacts with diethyl malonate to the form ethyl 2-ethoxy-4-oxo-1,4-dihydroquinoline-3-carboxylate. The compound formed was then hydrolysed under reflux with 20ml of 10%  dilute hydrochloric acid to produce ethanol and 2-hydroxy- 4-quinolone-3-carboxylic acid, which was crystallized with ethanol to form white coloured crystals (1.23 g, 82.3 % yield).