Solid-liquid phase transfer catalysis improved method of preparing 2,4-difluoroaniline
AssigneeMerck & Co., Inc.
InventorsRoger J. Tull, Leonard M. Weinstock, Ichiro Shinkai
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Abstract
A method of preparing 2,4-difluoroaniline by reacting 2,4,5-trichloronitrobenzene with a fluorinating agent in the presence of a solid-liquid phase interface, and utilizing a phase transfer catalyst to form 2,4-difluoro-5-chloronitrobenzene, followed by hydrogenation with hydrogen in the presence of a hydrogenation catalyst to form 2,4-difluoroaniline.
Claims10
A method of preparing 2,4-difluoroaniline comprising the steps of
- (a) fluorinating 2,4,5-trichloronitrobenzene in a solid-liquid phase system, under anhydrous conditions, wherein the solid phase comprises a fluorinating agent selected from NaF, KF, CsF, C.sub.1-4 alkyl quaternary ammonium fluoride, and mixtures thereof;
- and the liquid phase comprises an organic solvent in which the 2,4,5-trichloronitrobenzene is soluble and in which the fluorinating agent is essentially insoluble;
- and the fluorination is carried out in the presence of one or more quaternary compound solid-liquid phase transfer catalysts of the formula ##STR4## where M is nitrogen, arsenic, phosphorus, antimony, or bismuth;
- X.sup..crclbar. is an anion capable of dissociating from the M.sup..sym. cation;
- and R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are monovalent hydrocarbon radicals selected from alkyl, alkenyl, alkynyl, aryl, aralkyl, alkaryl, and cycloalkyl, which together have a total of at least 18 carbon atoms;
- to form 2,4-difluoro-5-chloronitrobenzene;
- and
- (b) hydrogenating the 2,4-difluoro-5-chloronitrobenzene with hydrogen in the presence of a hydrogenation catalyst to form 2,4-difluoroaniline.
A method of preparing 2,4-difluoro-5-chloronitrobenzene comprising the step of fluorinating 2,4,5-trichloronitrobenzene in a solid-liquid phase system, under anhydrous conditions, wherein the solid phase comprises a fluorinating agent selected from NaF, KF, CsF, C.sub.1-4 alkyl quaternary ammonium fluoride, and mixtures thereof;
- and the liquid phase comprises an organic solvent in which the 2,4,5-trichloronitrobenzene is soluble and in which the fluorinating agent is essentially insoluble;
- and the fluorination is carried out in the presence of one or more quaternary compound solid-liquid phase transfer catalysts of the formula:
- ##STR5## where M is nitrogen, arsenic, phosphorus, antimony, or bismuth;
- X.sup..crclbar. is an anion capable of dissociating from the M.sup..sym. cation;
- and R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are monovalent hydrocarbon radicals selected from alkyl, alkenyl, alkynyl, aryl, aralkyl, alkaryl, and cycloalkyl, which together have a total of at least 18 carbon atoms;
- to form 2,4-difluoro-5-chloronitrobenzene.
Dependencies are inferred from the claim text.