Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Patent
1997-12-01
1999-06-29
Richter, Johann
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
C07C25500
Patent
active
059170808
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved process for preparing 2-cyano-3,3-diarylacrylic esters of the general formula I ##STR4## where R.sup.1 and R.sup.2 are hydrogen, C.sub.1 -C.sub.4 -alkyl groups, C.sub.1 -C.sub.4 -alkoxy groups or di(C.sub.1 -C.sub.4 -alkyl)amino groups and R.sup.3 is a C.sub.4 -C.sub.18 -alkyl group which can be interrupted by ether-functional oxygen atoms, by reacting the appropriate benzophenone imines with the appropriate 2-cyanoacetic esters.
2-Cyano-3,3-diarylacrylic esters are highly effective UV absorbers which are used in particular as light stabilizers in plastics and cosmetic products.
2. Description of the Background
It is generally known to prepare compounds of type I from the benzophenones by reaction with cyanoacetic esters (see, for example, EP-A1 430 023, US-A 3 215 724 and DE-Al 43 14 035).
Although this reaction requires the relatively high temperatures of from 70 to 130.degree. C., it takes place only slowly and therefore requires the use of a catalyst, which must subsequently be removed from the product. In addition, unwanted concomitant substances are produced and, for this reason, elaborate purification steps must follow the reaction.
It is furthermore known (Bull. Chem. Soc. Fr. (1963) 1576 (G. Charles)) to prepare ethyl 2-cyano-3,3-diphenylacrylate from benzophenone imine and ethyl 2-cyanoacetate at 70 to 120.degree. C., but this reaction has the disadvantage that colored byproducts are produced at the reaction temperatures, and the liberated ammonia reacts to an interfering extent with the ester moiety of the molecule to give the corresponding amide ##STR5## ie. elaborate purification stages are also necessary in this case, especially in order to make the products suitable for use in cosmetic products.
SUMMARY OF THE INVENTION
It is an object of the present invention to make the compounds I available in a simpler and more economic manner than hitherto.
We have found that this object is achieved by an improvement in the process, defined at the outset, for preparing the compounds I, which comprises reacting a benzophenone imine of the general formula II ##STR6## with a cyanoacetic ester of the general formula III ##STR7## at from 20 to 60.degree. C. and, during this, continuously removing the liberated ammonia from the reaction mixture with the aid of a stream of gas or by reducing the pressure to 900-100 mbar.
DETAILED DESCRIPTION OF THE INVENTION
Compounds I which are particularly important with a view to the use properties are those where R.sup.1 and R.sup.2 are hydrogen, methyl or ethyl. Further preferred radicals R.sup.1 and R.sup.2 are methoxy, ethoxy and dimethylamino. The region of light absorption can be shifted somewhat by choice of the substituents R.sup.1 and R.sup.2 so that the compounds I can be suited to specific light stabilization requirements. The corresponding benzophenone imines II are known or obtainable by known methods (see, for example, Bull. Chem. Soc. cit. and German Patent Application P 44 42 138.9).
Particularly suitable cyanoacetic esters are those with a relatively long-chain alcohol component. Preferred cyanoacetic esters are those derived from 2-ethylhexanol and n-octanol, which are proven components of important light stabilizers. However, other alcohol residues, such as the various isomeric butanols, pentanols, hexanols, heptanols, nonanols, decanols, dodecanols or alcohols derived from long-chain fatty acids can also be constituents of cyanoacetic esters which can advantageously be used. Also suitable as R.sup.3 are the various polyoxyethylene radicals such as --CH.sub.2 --CH.sub.2 --O--CH.sub.2 --CH.sub.3, --CH.sub.2 --CH.sub.2 --O--CH.sub.2 --CH.sub.2 --O--CH.sub.2 --CH.sub.3 and their longer-chain homologs, which confer on the compounds I solubility properties which are advantageous in particular for cosmetic formulations.
The process according to the invention is particularly suitable for preparing liquid products I which cannot be separated from the startin
REFERENCES:
patent: 3215724 (1965-11-01), Strobel et al.
Societe Chimiques de France, Paris, Bulletin, vol. 1963, Georges Charles.
Aumuller Alexander
Beck Karl
Holderbaum Martin
Voit Guido
Witzel Tom
BASF - Aktiengesellschaft
Murray Joseph
Richter Johann
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