Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Patent
1994-09-21
1997-03-04
Rotman, Alan L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
544335, 546298, 546314, 546315, 548200, 5483335, 549 70, C07D23322, C07D21350, C07D23936, C07D27734
Patent
active
056080620
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE
This application is a 371 of PCT/EP 93/00094 filed Jan. 15, 1993.
DESCRIPTION
The present invention relates to a process for preparing trifluoromethyl ketones of the formula I ##STR3## where R is an unsubstituted or substituted aliphatic or aromatic hydrocarbon radical or an unsubstituted or substituted aliphatic or aromatic heterocyclic radical, wherein an alcohol of the formula II ##STR4## where R has the abovementioned meaning, is reacted in an aprotic solvent, preferably methylene chloride, chloroform, ethyl acetate, toluene, xylene or chlorobenzene, in the presence of 0.1-20 mol %, preferably of 1-10 mol %, based on the alcohol of the structure II employed, of a phase-transfer catalyst, with a 1-20% strength by weight aqueous solution of a compound of the structure IV or a 1-20% strength by weight aqueous solution of a compound generated in situ of the structure IV at temperatures from 0.degree. C. up to the boiling point of the mixture.
The compounds of the formula I are important starting products and intermediates in the synthesis, for example, of pharmaceuticals, plant protection agents (EP-A-0386 715), plastics (U.S. Pat. No. 3,342,778), surface-active substances (DD 2397 88 A1), materials for non-linear optics (WO 91/08198), liquid crystals and dyes.
It is known that trifluoromethyl alcohols are inert towards a multiplicity of oxidizing agents (Tetrahedron (1991), 47 (20/21), 3207).
Reactions of alcohols of the structure II with dimethyl sulfoxide at -55.degree. C. in the presence of oxalyl chloride (AU-B-52 881/86) to form the ketones I require more than 3 mol of the oxidizing agent per mol of the alcohols II employed. The procedure for the reaction must be seen as being disadvantageous for the industrial scale. The use of large quantities of oxalyl chloride is unacceptable for economic reasons. The dimethyl sulfide arising during the reaction must be considered disadvantageous from the ecological point of view.
The preparation of trifluoromethyl ketones of the structure I by oxidation of alcohols of the formula II using the Dess-Martin reagent (J. Org. Chem. (1989), 54, 661) requires the use of expensive, hypervalent iodine compounds which are hazardous and are not available commercially. In particular, the industrial use of Dess-Martin reagent is to be considered disadvantageous from the economic and safety points of view.
The use of alkaline permanganate solution (Tetrahedron Lett. (1986), 27 (2), 135) for the oxidation of compounds of the structure II is limited to water-soluble trifluoromethyl alcohols and gives results which are not very reproducible (J. Org. Chem. 1989, 54, 661).
The use of chromic acids for synthesizing the type I compounds from the alcohols II (J. Org. Chem. (1968), 33 (3), 1016) requires drastic reaction conditions and reaction times of several days, and can therefore be used to advantage only for inert, perhalogenated alcohols. The resulting chromium salt waste must be considered disadvantageous from the economic and ecological points of view.
All these disadvantages which have been described are avoided by the process according to the invention, which is very simple to perform and which is also suitable for continuous operation. Under the conditions according to the invention, the products I can be obtained in high yields, e.g. up to 90% of theory, and at high purity, using readily available, economically advantageous oxidizing agents of the structure IV. At the same time the radical R can be varied very widely.
When in the form of a hydrocarbon radical, R in formula I contains preferably 1 to 30, particularly 1 to 20 and in particular 1 to 12 carbon atoms, and when in the form of a heterocyclic radical, R contains preferably 1 to 4 hetero atoms in the ring. The ring contains preferably 4 to 8, particularly 5 or 6 ring members. The hetero atoms are preferably O, S or N and identical or different hetero atoms may be contained within the ring.
R in the form of an aliphatic hydrocarbon radical is preferably unsubstituted or substituted alkyl, alkeny
REFERENCES:
patent: 3996259 (1976-12-01), Lee et al.
Linderman, Russell J., et al., "An Efficient Procedure for the Oxidation of Fluorinated Carbinols", Tetrahedron Letters 28(37): 4259-4262 (1987).
Jean-Pierre B egu e and Dani ele Bonnet-Delpon, Tetrahedron Report No. 290, "Preparation of Trifluoromethyl Ketones and Related Fluorinated Ketones", Tetrahedron vol. 47, No. 20/21, pp. 3207-3258, 1991.
D oller Uwe
Scharbert Bernd
Weisse Laurent
Hoechst Schering AgrEvo GmbH
Rotman Alan L.
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