Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1998-03-12
2000-06-06
Gerstl, Robert
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C07C20500
Patent
active
060720808
ABSTRACT:
A process for the purification of a compound of general formula I: ##STR1## wherein R.sup.1 is hydrogen or C.sub.1 -C.sub.6 alkyl, C.sub.2 -C.sub.6 alkenyl or C.sub.2 -C.sub.6 alkynyl, any of which may optionally be substituted with one or more substituents selected from halogen and hydroxy; or COOR.sup.4, COR.sup.6, CONR.sup.4 R.sup.5 or CONHSO.sub.2 R.sup.4 ;
R.sup.4 and R.sup.5 independently represent hydrogen or C.sub.1 -C.sub.4 alkyl optionally substituted with one or more halogen atoms;
R.sup.6 is a halogen atom or a group R.sup.4 ;
R.sup.2 is hydrogen or halo; and
R.sup.3 is C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 alkenyl or C.sub.2 -C.sub.4 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, loading being defined as: ##EQU1## and wherein the temperature to which the solution is cooled for crystallisation is not greater than about 30.degree. 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 followed by back extraction with fresh crystallising solvent. The process is particularly useful for purifying acifluorfen produced via a route starting with m-cresol.
REFERENCES:
patent: 5446197 (1995-08-01), Sandison
Brown Stephen Martin
Gott Brian David
Gray Thomas
Nady Louie Akos
Tavana Seyed Mehdi
Burkhard Dianne
Gerstl Robert
Zeneca Limited
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