To provide a method for producing the subject compound in high yield and high purity without isolating urea formed as an intermediate by reacting an anthranilic acid with an isocyanate.
An anthranilic acid represented by formula I (R2 to R5 are each H, a halogen, a 1-6C alkyl or a 1-6C alkoxy) is reacted with an isocyanate represented by formula II (R1 is a 6-10C aryl which is unsubstituted or substituted with up to 5 halogens) in an organic aprotic solvent at 0-200°C, preferably 20-150°C temperature and the resultant reaction mixture is then treated with an acid, especially a strong organic acid or an inorganic acid (preferably sulfuric acid or hydrochloric acid) without isolating urea formed as an intermediate to produce a qinazoline-2,4-dione represented by formula II. The amount of the acid used is within the range of 0.2-5 mol, preferably 0.5-3 mol based on 1 mol of the compound represented by formula I. After completing the reaction of the compounds represented by formulae I and II, the reaction mixture is advantageously stirred for an additional period (e.g. 1/2 to 5 hr).
KURAUSUUKURISUTEIAN PETSUTSU
BORUFUGANGU KIIRU