Patent ID: 8563749

Claim:
A process for preparing a compound of formula (I): in which R 1a to R 1d independently of one another are selected from the group consisting of: hydrogen, fluorine, chlorine, bromine, and trifluoromethyl; (C 1 -C 6 )-alkyl, the alkyl radical being unsubstituted or being substituted by one or more substituents selected from the group consisting of (C 1 -C 4 )-alkoxy and (C 3 -C 7 )-cycloalkyl; (C 3 -C 7 )-cycloalkyl, the cycloalkyl radical being unsubstituted or being substituted by one or more substituents selected from the group consisting of (C 1 -C 4 )-alkyl, (C 3 -C 7 )-cycloalkyl, and (C 1 -C 4 )-alkoxy; (C 1 -C 6 )-alkoxy, the alkoxy radical being branched or unbranched and being unsubstituted or substituted by one or more substituents selected from the group consisting of (C 1 -C 4 )-alkoxy and (C 3 -C 7 )-cycloalkyl; (C 3 -C 7 )-cycloalkoxy, the cycloalkoxy radical being unsubstituted or being substituted by one or more substituents selected from the group consisting of (C 1 -C 4 )-alkyl and (C 1 -C 4 )-alkoxy; (C 1 -C 6 )-alkylthio, the alkylthio radical being branched or unbranched and being unsubstituted or substituted by one or more substituents selected from the group consisting of (C 1 -C 4 )-alkyl and (C 1 -C 4 )-alkoxy; (C 3 -C 7 )-cycloalkylthio, the cycloalkylthio radical being unsubstituted or being substituted by one or more substituents selected from the group consisting of (C 1 -C 4 )-alkyl and (C 1 -C 4 )-alkoxy; and phenyl or 1-naphthyl or 2-naphthyl or a five- or six-membered heteroaromatic ring having 1 to 2 heteroatoms, the heteroatoms being selected independently of one another from the group consisting of O or N, and the aryl or heteroaryl radical being unsubstituted or being substituted by one or more substituents selected from the group consisting of (C 1 -C 4 )-alkyl, (C 1 -C 4 )-alkoxy, (C 3 -C 7 )-cycloalkyl, and (C 1 -C 4 )-alkylthio; starting from a compound of formula (II): in which: R 1a to R 1d are defined as in formula (I); and R 2 is an unsubstituted or substituted (C 1 -C 14 )-alkyl, (C 3 -C 7 )-cycloalkyl, benzyl or a CH 2 —C(O)O—(C 1 -C 6 )-alkyl; which comprises: a) dissolving or suspending a compound of the formula (II) in a polar solvent; b) adding a sulfur-containing salt to the solution or suspension; and c) heating the reaction mixture under reflux at a temperature which corresponds at most to the boiling temperature of the polar solvent.