The present invention relates to heteroaryl compounds of formula (I) or a compound in the form of a stereoisomer, an agriculturally acceptable salt, a tautomer, an isotopic form, a N-oxide, a S-oxide, a prodrug or mixture thereof. The present invention further relates to the use of a compound of formula (I). Furthermore, the present invention relates to methods for combating phytopathogenic harmful fungi, which methods comprising the steps of treatment of the phytopathogenic fungi, the plant or the plant propagation material selected from seeds, roots, fruits, tubers, bulbs, rhizomes, shoots, sprouts and other parts of plants, including seedlings and young plants to be protected against fungal attack, stored materials or harvest, or alternately the locus or soil or soil substituents or surfaces therefrom, with at least one compound of formula (I).