| 摘要 |
A process for preparing the polymorph I of the anhydrate of 2-Chloro-N-(4'-chlorobiphenyl-2-yl)-nicotinamide (boscalid) of the formula I: is provided, the process comprising the steps of: a) dissolving the polymorph II of the anhydrate of boscalid in a first solvent in an amount and at conditions allowing dissolution of the polymorph II of the anhydrate of boscalid; b) combining the resulting solution with a second solvent at a temperature in the range of from -30 to 30°C, the second solvent being different from the first solvent and selected from the lower alkanes so as to precipitate a solid; and c) recovering the solid to obtain the polymorph I of the anhydrate of boscalid. Preferably, the first solvent is a linear or cyclic ether, a ketone and/or a halogenated alkane. More preferably, the first solvent is either dichloromethane or tetrahydrofuran (THF). The preferred second solvent is n-hexane. |
