GB674847A - Improvements in and relating to the preparation of pyrimidopyrazine derivatives - Google Patents

Abstract

Pyrimidopyrazines of the general formula <FORM:0674847/IV (b)/1> wherein R1 and R2 are amino, alkyl, aryl or hydroxy groups, R3 and R4 are alkyl or aryl groups (which may be substituted), or R3 and R4 together may form parts of a heterocyclic or homocyclic ring, are prepared by condensing with one another either a 5-nitroso-4-amino-pyrimidine of the general formula <FORM:0674847/IV (b)/2> with a ketone of the general formula <FORM:0674847/IV (b)/3> or a 4-aminopyrimidine of the general formula <FORM:0674847/IV (b)/4> with an a -nitroso-ketone of the general formula <FORM:0674847/IV (b)/5> or a tautomer thereof, in each method, R1, R2, R3 and R4 have the above significance. Both reactions may be carried out in the presence of an acid catalyst, e.g. hydrochloric acid or glacial acetic acid. The reactants may be dissolved in a mutual solvent. The preferred reaction temperature is from 100 to 200 DEG C. In the examples, 2,4 - diamino - 6,7 - diphenyl-pyrimido-pyrazine is prepared from 5-nitroso-2,4,6-triaminopyrimidine and desoxybenzoin, 2,4 - diamino - 6 - phenyl - 7 - methylpyrimido-pyrazine is prepared from 5-nitroso-2,4,6-tri-aminopyrimidine and benzylmethylketone, 2,4-diamino - 6,8 - dihydroxypyrimidopyrazine (6,7,51,41) pyrimidine is prepared either from 5-nitroso-2,4,6-triaminopyrimidine and barbituric acid or from 2,4,6-triaminopyrimidine and 5 - nitroso - 2,4,6 - trihydroxypyrimidine (tautomeric form of 5-mono-oxime of 5,6-diketo uracil), 2,4,6,8-tetrahydroxypyrimidopyrazino-(6,7,51,41) pyrimidine is prepared either from 5-nitroso-4-amino-2,6-dihydroxypyrimidine and barbituric acid or from 5-nitroso-2,4,6-trihydroxypyrimidine and 4-amino-2,6-dihydroxypyrimidine. The sample furnished under the provisions of Sect. 2 (5) comprises 2,4-diamino-acenaphtho-(11,21,6,7)-pyrimidopyrazine (prepared from 5-nitroso-2,4,6-triaminopyrimidine and acenaphthenone.