PROCESS FOR THE PREPARATION OF PYRIMIDO[5,4-G]PTERIDINE DERIVATIVES

Preparation of pyrimido[5,4-g]pteridine of formula (I) wherein A1, A2, A3 an d A4 are each independently of the others -NR1R2, wherein R1 and R2 are hydrogen, C1-C8alkyl, -CO-C1-C8alkyl, -CO-C6-C14aryl, -COO-C1-C8alkyl, -COO- C6- C14aryl, -CONH-C1-C8alkyl or -CONH-C6-C14aryl, or -OH, -SH, hydrogen, C1- C8alkyl, C1-C8alkoxy, or C6-C14aryl or -O-C6-C14aryl each unsubstituted or mono- or poly- substituted by halogen, nitro, cyano, -OR10, -SR10, -NR10R11, - CONR10R11, -COOR10, -SO2R10, -SO2NR10R11, -SO3R10, -NR11COR10 or by - NR11COOR10, wherein R10 and R11 are each independently of the other hydrogen , C1-C8alkyl, C5-C12cycloalkyl or C2-C8alkenyl, by a) reacting the pyrimidine of formula (II) with the pyrimidine of formula (III) in the presence of an acid and, if desired, of a solvent, the molar ratio of the acid to the compound o f formula (II) being in the range of from 100:1 to 1:1, and b) subsequently treating the resulting reaction mixture with a base, and novel pyrimido[5,4- g]pteridine salts and their use.