| abstract |
Claim 1: A method for preparing a compound of formula (1), characterized in that it comprises the following step (A): wherein a compound of formula (2) is allowed to react with a vinyl sulfone compound of formula (3), in the which R represents an alkyl group, such as a methyl, ethyl or n-propyl group for example, or an aryl group, such as a phenyl group for example, optionally in an aromatic hydrocarbon solvent, such as toluene for example, preferably at the reflux temperature of said solvent, thereby providing said compound of formula (1). |