Herbicidal pyrimidine derivatives of the formula ##STR1## in which R.sup.1 stands for optionally substituted alkyl,R.sup.2 stands for an optionally substituted radical from the group consisting of alkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, heteroaryl and heteroarylalkyl, andstands for halogen, amino, cyanoamino or for an optionally substituted radical from the series comprising alkoxy, alkylthio, alkylamino and dialkylamino.Intermediates of the formula ##STR2## in which R.sup.3 is optionally substituted alkyl or benzyl, and n is 0 or 2,are also new.