The invention relates to novel triazolopyrimidines of formula (I), in which R1 represents amino, or represents optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, alkoxy, alkenyloxy, alkynyloxy, cycloalkyloxy, alkylamino, dialkylamino, alkenylamino, alkynylamino, cycloalkylamino, N-cycloalkyl-N-alkylamino, alkylidenamino or heterocyclyl, R2 represents hydrogen or optionally substituted alkyl, alkenyl, alkynyl or cycloalkyl, or R1 and R2, together with the nitrogen atom, to which they are bonded, form an optionally substituted heterocyclic ring, R3 represents an optionally mono to tetrasubstituted aryl, R4 represents halogen, cyano or optionally substituted alkoxy or dialkylamino and X represents halogen. The invention also relates to a method for producing said novel substances and to their use for combating undesired microorganisms. The invention further relates to novel intermediate products of formulas (II), (IV) and (VIa), in addition to methods for the production thereof.