To a stirred solution of 0.65 g. (11.5 mM) of potassium hydroxide in 23 ml. of ethanol is added 2.07 g. (11.5 mM) of 6-methoxyphthalaldehydic acid. To the resulting cooled (10°) milky suspension is added 1.89 g. (11.75 mM) of 2-phenyl-5-oxazolone. The mixture is warmed to 25° and stirred at this temperature for 35 minutes. A light orange precipitate forms. The mixture is made acidic with 3.45 ml. of 4N sulfuric acid and the resulting mixture kept at 0° for 1.5 hours and filtered. The collected solid is washed with a small amount of cold ethanol and then hexane. Air-drying gives the oxazolone 4-(2-carboxy-3-methoxybenzylidene)-2-phenyl-5(4H)-oxazolone as a yellow solid, m.p. > 320°.
