A process for preparing quinazoline derivatives

A process for producing 1,2,3,4-tetrahydro-2,4-dioxo-quinazoline-1-yl acetic acid derivatives of the formula (I) in which R , R , R and R are mutually independently hydrogen, halogen, OH, NO2, (C1-C6)alkoxy, (C1-C6)alkyl, halogen-substituted (C1-C6)alkyl; R is hydrogen, (C1-C6)alkyl, phenyl where the alkyl or phenyl radical may also be substituted by halogen atoms; in which an anthranilic acid derivative of formula (II), in which R to R have the above meanings and R is hydrogen, (C1-C6)alkyl or phenyl, where the alkyl or phenyl radical may also be substituted by halogen atoms, is reacted with a metal cyanate and hydrogen chloride in the presence of an inert solvent.