NOVEL PYRIMIDONE DERIVATIVES

Pyrimidone derivatives of the formula I wherein n is the integer 1 or 0; A1 and A2 are independently methylene or mono-lower alkyl or di-lower alkyl methylene; X is methylene, mono-lower alkyl or di-lower alkyl methylene, nitrogen or lower alkyl nitrogen; R is hydrogen or lower alkyl; and Y and Z taken together are the group =NR5, or R and Z taken together form a N-C-bond and Y is a group -N(H)R5; R1, R2 and R3 are hydrogen, lower alkyl or lower alkoxy, or R1 and R2 or R2 and R3 taken together are methylenedioxy or ethylenedioxy; R4 is hydrogen or lower-alkyl; R5 is phenyl or phenyl substituted by one or more of R6, R7 and R8 which, independently, are chlorine, fluorine, bromine, lower-alkyl or lower-alkoxy; and provided that at least one of the methylene groups A1 and A2 is mono-lower alkyl or di-lower alkyl methylene, when R4 is hydrogen and n is 0, and physiologically compatible salts thereof which have blood platelet aggregation-inhibiting activity or have activity on the circulatory system, are described. The compounds of formula I are obtained starting from corresponding chlorinated or brominated pyrimidone derivatives.