Triazolopyrimidines of the formula I in which the substituents are as defined below: R1, R2 are hydrogen, alkyl, haloalkyl, cycloalkyl, halocycloalkyl, alkenyl, haloalkenyl, cycloalkenyl, halocycloalkenyl, alkynyl, haloalkynyl or phenyl, naphthyl, or a five- or six-membered saturated, partially unsaturated or aromatic heterocycle which contains one to four heteroatoms from the group consisting of O, N and S, R1 and R2 together with the nitrogen atom to which they are attached may also form a five- or six-membered heterocyclyl or heteroaryl which is attached via N and may contain a further heteroatom from the group consisting of O, N and S as ring member and may be substituted as defined in the description; L1, L2 are hydrogen, cyano, haloalkyl, alkoxy, alkenyloxy or C(═O)A, where at least one group L1 or L2 is not hydrogen; A is hydrogen, hydroxyl, alkyl, alkoxy, haloalkoxy, C1-C8-alkylamino or dialkylamino; L3 is hydrogen, halogen, cyano, nitro, haloalkyl, alkoxy or alkoxycarbonyl; X is halogen, cyano, alkyl, haloalkyl, alkoxy or haloalkoxy; processes and intermediates for preparing these compounds, compositions comprising them and their use for controlling phytopathogenic harmful fungi.