| 摘要 |
<p>A process for the purification of a compound of general formula (I), wherein R1 is hydrogen or C1-C6 alkyl, C2-C6 alkenyl or C2-C6 alkynyl, any of which may optionally be substittuted with one or more substituents selected from halogen and hydroxy; or COOR?4, COR6, CONR4R5¿ or CONHSO?2R4; R4 and R5¿ independently represent hydrogen or C¿1?-C4 alkyl optionally substituted with one or more halogen atoms; R?6¿ is a halogen atom or a group R4; R2 is hydrogen or halo; and R3 is C1-C4 alkyl, C2-C4 alkenyl or C2-C4 alkynyl, any of which may optionally be substituted with one or more halogen atoms; or halo; or, where appropriate, a salt thereof; from a mixture containing the compound of general formula (I) together with one or more isomers or di-nitrated analogues thereof; the process comprising dissolving the mixture in a suitable crystallisation solvent and recrystallising the product from the resulting crystallisation solution wherein the crystallisation solution contains not more than 25 % loading of the compound of general formula (I) and wherein the temperature to which the solution is cooled for crystallisation is not greater than about 30 °C; wherein, after the addition of the crystallising solvent but before recrystallisation, the crystallisation solution is subjected to at least one wash with an aqueous solution having an acid pH. The process is particularly useful for purifying acifluorfen.</p> |
