| 摘要 |
A process for preparing a compound of formula (II): <CHEM> or a tautomer or salt thereof in substantially pure form wherein R<1> is C1-6 alkyl optionally substituted by one or more halogen atoms; R<3> is hydrogen, fluorine, chlorine, bromine or iodine, C1-6 alkyl, trifluoromethyl or a cyano group; R<4> is hydrogen, fluorine, chlorine, bromine, iodine or trifluoromethyl; R<5> is fluorine, chlorine, bromine, iodine or trifluoromethyl; and R<6> is hydrogen or C1-4 alkyl; which process comprises nitrating a compound of formula (III): <CHEM> or a salt thereof wherein R<1>, R<3>, R<4>, R<5> and R<6> are as defined above, in a solvent which is resistant to nitration under the desired reaction conditions and suitable for purification of the product of formula (II), heating the resultant solution to a temperature sufficient to at least partially dissolve the desired product and impurities and cooling the solution to precipitate the compound of formula (II) in substantially pure form. |
