The invention relates to a process comprising the process steps of: a) initially charging an ether having from 3 to 30 carbon atoms; b) adding a phosphine ligand and a compound comprising Pd, or adding a comprising Pd and a phosphine ligand; c) feeding in CO; d) heating the reaction mixture, with conversion of the ether; wherein the phosphine ligand is a compound of formula (I) where m and n are each independently 0 or 1; R1, R2, R3, R4 are each independently selected from —(C1-C12)-alkyl, —(C3-C12)-cycloalkyl, —(C3-C12)-heterocycloalkyl, —(C6-C20)-aryl, —(C3-C20)-heteroaryl; at least one of the R1, R2, R3, R4 radicals is a —(C3-C20)-heteroaryl radical; and R1, R2, R3, R4, if they are —(C1-C12)-alkyl, —(C3-C12)-cycloalkyl, —(C3-C12)-heterocycloalkyl, —(C6-C20)-aryl or —(C3-C20)-heteroaryl, may each independently be substituted by one or more substituents selected from —(C1-C12)-alkyl, —(C3-C12)-cycloalkyl, —(C3-C12)-heterocycloalkyl, —O—(C1-C12)-alkyl, —O—(C1-C12)-alkyl-(C6-C20)-aryl, —O—(C3-C12)-cycloalkyl, —S—(C1-C12)-alkyl, —S—(C3-C12)-cycloalkyl, —COO—(C1-C12)-alkyl, —COO—(C3-C12)-cycloalkyl, —CONH—(C1-C12)-alkyl, —CONH—(C3-C12)-cycloalkyl, —CO—(C1-C12)-alkyl, —CO—(C3-C12)-cycloalkyl, —N—[(C1-C12)-alkyl]2, —(C6-C20)-aryl, —(C6-C20)-aryl-(C1-C12)-alkyl, —(C6-C20)-aryl-O—(C1-C12)-alkyl, —(C3-C20)-heteroaryl, —(C3-C20)heteroaryl-(C1-C12)-alkyl, —(C3-C20)-heteroaryl-O—(C1-C12)-alkyl, —COOH, —SO3H, —NH2, halogen; and wherein no alcohol is added to the reaction mixture.