Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1992-11-17
1994-05-17
Siegel, Alan
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
570143, 546180, 546346, 564442, C07C 4302, C07C 2200
Patent
active
053130014
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of .alpha.-fluorostyrenes by reaction of halogenated aromatics with fluoroolefins in the presence of a palladium catalyst.
Processes for the preparation of .alpha.-fluorostyrenes are known in the state of the art.
Thus the synthesis of .alpha.-fluorostyrene was described for the first time in 1962 by Matsuda et al. (K. Matsudo, J. A. Sedlak, J. J. Noland, G. C. Gleckler, J. Org. Chem. 27, 4015 (1962)), who reacted phenylacetylene or .alpha.-chlorostyrene with hydrofluoric acid. .alpha.,.alpha.-Difluoroethylbenzene is formed in the first stage and .alpha.-fluorostyrene can be obtained therefrom by pyrolysis at 400.degree. C. The yields are very low in this reaction, it being possible to isolate 20% of .alpha.-fluorostyrene in the most favorable cases.
Higher yields of .alpha.-fluorostyrene can be obtained by reaction of bromine fluoride with styrene (L. Heckes, M. Hanack, Synthesis, 217, 1978). In this process, bromine fluoride is produced in situ and added on to styrene and, in a second step, .alpha.-fluorostyrene is formed in 63% yield with the elimination of hydrogen bromide. The addition of bromine fluoride on to substituted olefins takes place with high regioselectivity here. Because of its high reactivity and instability, bromine fluoride cannot be used directly for the synthesis but has to be produced in situ, e.g. from N-bromoacetamide and hydrogen fluoride in absolute ether. A further disadvantage is the generally difficult manipulability and toxicity of interhalogen compounds.
Palladium-catalyzed coupling reactions of fluorovinyl zinc compounds with aryl iodides were described in 1986 by Heinze and Burton (P. L. Heinze, D. J. Burton, J. Fluorine Chemistry 31 (1986) 1, 115).
The reaction of bromo- or iodo-trifluoroethene with zinc by this method yields a mixture of trifluorovinyl zinc bromide or iodide and bistrifluorovinylzinc, which react with aryl iodides under palladium catalysis to give styrene derivatives.
The yields which can be achieved are up to max. 74% in this two-stage reaction.
The object of the present invention was therefore to develop a process for the preparation of .alpha.-fluorostyrenes which can be carried out in a simple and uncomplicated manner, in which the starting materials can be conveniently manipulated and which is characterized by a high purity of the end products and by good yields.
The invention thus relates to a process for the preparation of .alpha.-fluorostyrenes by reaction of halogenated aromatics with fluoroolefins in the presence of a palladium catalyst, via a one-stage reaction, which is distinguished by good yields and the formation of very small amounts of by-products and also in that it is carried out rapidly and in an uncomplicated manner. In the process according to the invention, halogenated aromatics, preferably bromoaryl or iodoaryl compounds, are added on to fluoroolefins, under palladium catalysis, in a water-miscible organic solvent. Bases can be added to the reaction mixture here, secondary or tertiary amines preferably being used and the reaction being carried out at a temperature of between 50.degree. and 180.degree. C.
The reaction product is separated off by subsequent vacuum distillation and has purities of more than 95% with preparative yields of 30 to 80%. The GC yields are 50 to 90%.
The process according to the invention is characterized in that a halogen-substituted aromatic (I), preferably a bromine- or iodine-substituted aromatic, are (sic) reacted with a fluorine-substituted ethylene (II) in the presence of a palladium catalyst to give an .alpha.-fluorostyrene. The halogenated aromatic can be substituted in the ortho, meta or para position, especially in the meta or para position, the radical R being a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.4 -alkyl group, a C.sub.1 -C.sub.5 -alkoxy group, an amino, alkylamino or dialkyl amino group, an aryl radical or a fused aryl or hetero aryl ring, a hydroxyl or hydroxyalkyl group, a tri fluoromethyl or perfluoroalkyl group or
REFERENCES:
patent: 2752400 (1956-06-01), Prober
Patent Abstracts of Japan 8, No. 7 (1984) 58-174 335.
Patent Abstracts of Japan 7, No. 242 (1983) 58-131 921.
Matsuda et al., J. Org. Chem. 27 (1962) 4015-20.
Heckes et al., Synthesis (1978) 217-220.
Heck, R. F., Organic Reactions 27 (1982) 345-90.
Heinze et al., J. Fluorine Chem. 31 (1986) 115-119.
Walter et al., Chem. Abstracts 114 (1991) 186116t.
Heitz Walter
Knebelkamp Arno
Hoechst Aktiengesellschaft
Siegel Alan
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