Abstract: The subject matter of the invention is the process for the preparation of mixed ethers of formula I, wherein Ar represents an aromatic or one or more heteroatom-containing moiety, optionally substituted by one or more C1-4 alkoxy, methylenedioxy, C1-4 alkyl, halogen, C1-4 haloalkyl or nitro-group, and/or condensed with a benzene ring; R1 and R2 independently mean hydrogen, C1-4 alkyl, C1-4 haloalkyl, C2-4 alkenyl, phenyl, substituted phenyl, C3-6 cycloalkyl group, R3 means C3-6 alkynyl, optionally substituted by one or more C1-6 alkyl, C3-6 alkenyl, C3-6 alkynyl, C1-6 haloalkyl group, or halogen atom, R3 also means a C1-4 alkyloxy-C1-4 alkyloxy-C1-4 alkyl group.