Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1999-01-19
2000-12-26
Siegel, Alan
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C07C 2513
Patent
active
061662712
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process which is useful for the synthesis of hydrocarbon-based compounds containing fluorine on a carbon of an alkyl chain, by exchange between a halogen of a higher row and fluorine by means of a reagent containing fluorine at least partially in the form of complex salts. The invention relates more particularly to a process for obtaining derivatives containing fluorine on a carbon atom bearing groups containing unsaturation or double bonds.
Fluoro compounds are generally difficult to obtain. The reactivity of fluorine is such that it is difficult, or even impossible, to obtain fluoro derivatives directly.
One of the techniques most commonly used for manufacturing fluoro derivatives consists in reacting a halo, generally a chloro, derivative in order to exchange the halogen with an inorganic fluorine, generally an alkali metal fluoride, in general of high atomic weight.
In general, the fluoride used is potassium fluoride, which constitutes a satisfactory economic compromise.
Under these conditions, many processes such as, for example, those described in Certificate of Addition No. 2,353,516 and in the article Chem. Ind. (1978)--56 have been described and used industrially to obtain aryl fluorides, onto which aryls are grafted electron-withdrawing groups.
Except for the case in which the substrate is particularly suitable for this type of synthesis, this technique has drawbacks, of which the main ones will be analysed below.
The reaction requires reagents, for instance alkali metal fluorides such as potassium fluoride, which are made relatively expensive due to the specifications they must meet in order to be suitable for this type of synthesis; they must be very pure, dry and in a suitable physical form.
In addition, this reaction does not work for an entire class of products, in particular those bearing [lacuna] on the halophoric carbon (i.e. the carbon bearing the halogen(s) intended to be exchanged with fluorine).
Reagents such as hydrofluoric acid in liquid form or diluted with dipolar aprotic solvents are also used. However, hydrofluoric acid is too powerful a reagent and often leads to unwanted polymerization reactions or to tars.
In this case, and in particular when derivatives are desired containing fluorine on a carbon of alkyl type (including aralkyl) which is electron-poor due to the presence of groups of electron-withdrawing type, a person skilled in the art is confronted with an alternative whose terms are hardly encouraging; alternatively, very harsh conditions are selected and tars are especially obtained, or alternatively mild reaction conditions are used and, in the best of cases, the unchanged substrate is recovered. Finally, it should be pointed out that certain authors have proposed carrying out exchanges using hydrofluoric acid salts as reagents in the presence of heavy elements in the form of oxides or fluorides. Among the elements used, mention should be made of antimony and heavy metals such as silver or quicksilver (mercury).
Another problem is the reaction selectivity: when there are several halogens to be exchanged on the same carbon, it is often difficult to exchange only some of them.
Consequently, one of the aims of the present invention is to provide a process which is capable of carrying out exchange between heavy halogens such as chlorine, on the one hand, and fluorine, on the other hand, by significantly improving the reaction specificity.
Another aim of the present invention is to provide a process which is capable of carrying out exchange between heavy halogens such as chlorine, on the one hand, and fluorine, on the other hand, using particularly mild reaction conditions. Another aim of the present invention is to provide a process which uses a source of fluoride whose morphology is less critical.
Another aim of the present invention is to provide a process which exchanges only one halogen atom out of two or three possible ones.
Another aim of the present invention is to provide a process which exchanges only two halogen atoms out of th
REFERENCES:
patent: 3966832 (1976-06-01), Lademann et al.
Database WPI, Section Ch, Week 8430, Derwent Publications Ltd., London, GB; Class E14, AN 84-185448 XP002022623 & JP 59 104 328 A (Hodogaya Chem Ind KK), Jun. 16, 1984.
J. Org. Chem. (Joceah, 00223263), 79; vol. 44, (22) pp. 3872-81, Univ. Southern California; Inst. Hydrocarbon Chem.; Los Angeles; 90007; CA, USA, XP002022622, Olah G.A. et al, "Synthetic methods and reactions. 63. Pyridinium poly(hydrogen fluoride) 30% pyridine--70% hydrogen fluoride): a convenient reagent for organic fluorination reactions", p. 3878, table XIV (1979).
Rhodia Chimie
Siegel Alan
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