PROCESS FOR PREPARING (3',5'-DIHYDROCARBYL-4'HYDROXYBENZYL)-1,2-DIKETONES

Abstract: Novel (3',5'-dihydrocarbyl-4'-hydroxybenzyl)-1,3-diketones are prepared by reacting an N,N-dihydrocarbyl-2,6-dihydro- carbyl-4-aminomethylphenol with a 1,3-diketone in the presence of a basic substance. The products are useful as antioxidants.

Description: PROCESS FOR PREPARING (3 * ,5* -DIHYDROCARBY -4' HYDROXYBENZYL)-1,2-DIKETONES This invention relates to novel and eminently useful (3 1 , 5'-dihydrocarbyl-4 1 -hydroxybenzyl)-1,3- diketones and the preparation and uses thereof as anti- oxidants for oxidizable organic materials when such materials are exposed to oxidative degradative condi¬ tions. The materials of the invention are prepared by reacting an N,N-dihydrocarbyl-2,6-dihydrocarbyl-4-amino- ethylphenol with a 1,3-diketone and a basic material, preferably selected from alkali metal hydroxides, alkali metal salts of a weak acid, alkaline earth metal hydroxides, alkaline earth metal salts of a weak acid, amine bases and mixtures of the same. Thus, in one embodiment of the invention there is provided a novel process for the preparation of (3',5'- dihydrocarb 1-4' -hydroxybenzyl)-1,3-diketones which com¬ prises reacting an N > N-dihydrocarbyl-2,6-dihydrocarbyl- 4-aminomethylphenol with a 1,3-diketone and a basic substance. In another embodiment of-the invention, there is provided a novel process for the preparation of (3 ' ,5 * - dihydrocarbyl-4'-hydroxybenzyl)-1 ,3-diketones which comprises reacting an N,N- ihydrocarbyl-2 / 6-dihydr , o- carbyl-4-aminomethylphenol with a 1,3-diketone and a basic material selected from the group consisting of 5. alkali metal hydroxides, alkali metal salts of a weak acid, alkaline earth metal hydroxides, alkaline earth metal salts of a weak acid, amine bases and mixtures of the same. Thus, in the present invention there is provided 0 a process for the preparation of (3' ,5'-dihydrocarbyl-4*- hydroxybenzyl)-l,3-diketones having the general formula which comprises reacting an N ,N-dihydrocarb l-2 ,6 -d i- 0 hydrocarbyl-4-aminomethylphenol of the general formula IjUREA t Oft-Pi . with a 1,3-diketone of the general formula R 5 COCH 2 COR 6 (II) in the presence of a basic substance wherein in the structura formulas above R-, and 2 are the same or different and are hydrogen or hydrocarbyl radicals having up to at least 40 carbon atoms with the provision that at least one of R-, or 2 must be other than hydrogen; R, and R, are the same or different and are linear, branched or unbranched alkyl, aralkyl or cycloalkyl radicals having up to at least 20 carbon atoms, and Re and Rg are the same or different and are linear or branched alkyl radicals having up to at least 20 carbon atoms. Representative examples of radicals described above are secondary radicals such as secondary butyl, secondary amyl, secondary octyl; tertiary radicals such as tertiary butyl, tertiary hexyl and tertiary decyl; alkyl radicals such as methyl, ethyl, propyl, butyl, nonyl, decyl, tetradecyl, hexadecyl, nonadecyl; aralkyl radicals such as methyl phenyl and pentyl phenyl, and cycloalkyl radicals such as cyclopentyl, cyclohexyl and cyclo heptyl radicals. Representative examples of the Group I compounds are N,N-di eth l,2,6-di-t-butyl-4-aminomethyl- phenol, N,N-dimethyl,2-methyl-6-isopropyl-4-amino- methylphenol,- N,N-dimethyl,2-methyl-6-t-butyl-4-amino- methylphenol, N,N-dimethyl,2,6-diisoρropyl-4-amiπomethyl- phenol, N,N-dimethyl,2-sec-butyl-4-aminomethylphenol, N,N-dimethyl,2-isopropyl-4-aminomethylphenol, N,N-dimethyl,2-t-butyl-4-aminome h lphenol, N,N-diethyl,2,6-di-t-butyl-4-aminomethylphenol, N,N-dioctyl,2,6-di-t-butyl-4-aminomethylphenol, N,N-dioctyl,2-ethyl-6-t-butyl-4-aminomethyl- phenol, N,N-dioctyl,2,6-diheptyl-4-aminomethylphenol, N,N-dioctyl,2-ethyl-6-methyl-4-aminomethyl- phenol, N,N-dioctyl,2-t-butyl-6-heptyl-4-aminomethyl- phenol, N-ethyl,N-methyl,2,6-di-t-butyl-4-aminomethyl- phenol, N-octyl,N-me h l, 2-methyl-6-ethyl-4-amino- methylphenol, 3, 5-di-t-butyl-4-hydroxybenzylpiperidine, 3,5-di-t-butyl-4-hydroxybenzylmorpholine, and 3, 5-di-t-butyl-4-hydroxybenzylρyrrolidine. O.V Representative examples of Group II 1, 3-dicarbonyl compounds are 2,4-pentanedione, 2,4-heptanedione, 4,6-nonanedione, 2,6-dimethy1-3, 5-he tanedione, 1-hexyl-l,3-butanedione, l-hexyl-2,4-pentanedione, and 1,3-dihexyl-l,3-propanedione. Representative examples of Group III benzylated 1,3-di- ketone compounds, functioning as antioxidants, are 3-(3' , 5'-di-t-butyl-4'-hydroxybenzyl)-2,4- pentanedione, 3-(3'-methyl-5 * -isopropyl-4' -hydroxybenzyl)- 2,4-pentanedione, 3-.(3 » -methyl-5*-t-buty1-4'-hydroxybenzyl)- 2,4-pentanedione, 3-(3' , 5'-diisoprop l-4'-hydroxybenzyl)-2,4- . pentanedione, 3-(3' -sec-butyl-4' -hydroxybenzyl) -2,4-pentane¬ dione, 3-(3'-isopropyl-4'-hydroxybenzyl)-2,4-pentane¬ dione, 3-(3' -t-butyl-4' -hydroxybenzyl)-2,4-pentane¬ dione, 3-(3'-ethyl-5* -methyl-4'-hydroxybenzyl)-2,4- heptanedione,. 5-(3' ,5' -dioctyl-4 1 -hydroxybenzyl)-4,6- nonanedione, 4-(3*-t-butyl-5'-he 1-4'-hydroxybenzyl)-2,6- dimethyl-3,5-heptanedione, 2-(3' ,5'-dioctyl-4'-hydroxybenzyl)-1-hexyl-l,3- butanedione, 3-(3* ,5' -dioctyl-4'-hydroxybenzyl)-l-hexyl-2,4- pentanedlone, and 2-(3' ,5' -dioctyl-4' -hydroxybenzyl)-1,3-dihexyl- 1,3-propanedione. In general, the basic reactant of the instant process may be any of the alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal salts of a weak acid, amine bases or mixtures of the same. These include sodium hydroxide, potassium hydroxide, barium hydroxide, rubidium hydroxide, cesium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, rubidium carbonate, potassium sulfite, sodium borate, potassium acetate, diazabicyclononane, pyridine, tetramethylguanidine and 1,4-diazabicyclo(2,2,2)-octane, and the like. The process of the invention is carried out by reacting the benzylamine starting material with at least 1 molar equivalent of 8-diketone reactant and 1 molar equivalent of base although an excess of either or both diketone and basic reactan-t can be used. A preferred range of -diketone reactant to benzylamine reactant is from 1 to 10 moles of -diketone per mole of benzyl- amine. A preferred range of basic reactant to benzyl¬ amine reactant ranges from 1 to 10 moles of base per mole of benzylamine. It should be stated, however, that the use of increasing amounts of basic material in the process tends to decrease the yield of desired benzylated 1,3-diketone product. The reaction is advantageously conducted at a temperature of from 50°C. to 500°C. While lower temperatures can be used, the reaction rates are generally correspondingly lower. Temperatures above 500°C. can be used, but excessive decomposition of the reaction components can occur. Reflux temperature at atmospheric pressure is effective and preferred. Typically, the reaction can be conducted at atmos¬ pheric pressure. However, higher pressures up to about 1000 psig may be used, if desired. The use of a solvent for the reaction mixture is not generally required, especially if an excess of 1, 3-dicarbonyl reactant is used. However, if desired, a solvent which is inert under the reaction conditions, i.e., those solvents which do not enter into the reaction, may be added to the reaction vessel. Useful solvents comprise aprotic solvents which include ethers such as diethyl ether, dibutyl ether, 1-ethoxyhexane, tetrahydrofuran, 1,4-dioxacιe, 1,3-dioxolane, diglyπje, 1, 2-diethox ethane, and tertiary amines such as pyridine, N-ethylpiperidine, triethylamine, tributyl- a ine, N.N-diphenyl-N-methylamine, N,N-dimethylalanine, etc. Especially useful solvents are dipolar aprotic solvents such as dimethyl sulfoxide, N.N-di ethylforma- ide, N,N-dimethylacεtamide, dimethyl sulfone, tetra- methylene sulfone, N-methylpyrrolidinone, acetonitrile and like materials. Other solvents which are inert under the reaction conditions may be used: for example, low boiling hydrocarbons, halogenated hydrocarbons, examples of which are benzene, toluene, tetrachloro- ethane, the chlorinated benzenes, the chlorinated toluenes, etc., and lower alkanols having up to about 6 carbon atoms. These include, methanol, ethanol, n-pro- panol, isopropyl alcohol, n-butanol, sec-butyl alcohol, t-butyl alcohol, n-pentanol, iso- pentyl alcohol, n-hexanol and isohexyl alcohol. The amount of solvent can be expressed as a volume ratio of solvent to benzylamine reactant. Suitable volume ratios of solvent to benzylamine reactant can be from 0/1 to 500/1 and preferably from 1/1 to 300/1. The mode of addition in the process is not particularly critical. Accordingly, it is convenient to add the benzylamine reactant to a mixture of the other - 9 - materials, add the 1, 3-dicarbonyl compound to a mixture of the other materials, add the basic reactant to a. mixture of the other materials, add the reactants to a mixture of the benzylamine and solvent, introduce all ingredients simultaneously into the reaction zone, or the like. The process should be carried out for the time sufficient to convert substantially all of the benzyl¬ amine reactant to the corresponding benzylated 1,3- diketone. The length of time for optimum yield will depend primarily upon the reaction temperature and the particular solvent, if any, used in the reaction. In general, excellent yields of the benzylated 1,3-dike- tones are obtained in from about two to twenty-four hours. Although not required, the process can be con¬ ducted in a substantially anhydrous reaction system, and accordingly, the components of the reaction system are brought together and maintained under a substantially dry, inert atmosphere. By "substantially anhydrous" is meant a reaction system wherein the total amount of water present is no more than about 5 percent by weight, based on the reaction mixture. When the amount of water in the system exceeds this, both reaction rate and yield of product decrease. The process may readily be conducted in a batch- wise, semi-batch or continuous manner and in conventional equipment. The process of the invention when run continous- ly can be illustrated schematically by the equation ' shown below. R, , R , , R<, e and Rg are the same radicals as described and exemplified above. + R5_.C0CH2..C0R6 c base Under the reaction conditions, the benzylamine reactant is alkylated to initially yield a quaternary ammonium salt of the benzylamine which subsequently eliminates a tertiary amine component from the salt to produce a quinone methide intermediate which undergoes nucleophilic attack by the- 1,3-diketone reactant tq form the desired benzylated 1,3-diketone product. During the course of the reaction some bis(hydroxyphenyl)methane by-product and a 4-(3-oxobutyl)phenol moiety can be formed. The benzylated 1,3-diketone product is easily separated from the reaction mixture by such means as dis¬ tillation, extraction, crystallization and other methods obvious to those skilled in the chemical processing art. The benzylated 1,3-diketone products prepared by the process of this invention have antioxidant properties and are capable of stabilizing polymers normally subject to oxidative degradation when incor- porated into the polymers using conventional techniques such as by addition to polymer lattices; or by addition to solid polymers on a mill or in a Banbury. Further, the novel compounds of this invention are effective antioxidants in both unleaded and leaded gasolines made from a wide variety of base stocks and for engine and industrial oils which are derived from crude petroleum or produced synthetically. The practice of this invention will be still further apparent by the following illustrative examples. o.r.Fi Example I A mixture of N,N-dimethyl-2,6-di-t-butyl-4,- aminomethyl-phenol (2.63 g, 10 mmols), sodium hydroxide (0.6 g, 15 mmols) and acetylacetone (24 mmols, 10% solution) was refluxed for 3 hours in a glass reaction 5 vessel. Acetylacetone was distilled under reduced pressure to afford an oily residue containing 3-(3',5'- _ di-t-butyl-4* -hydroxyphenyl)-2, -pentanedione (80% by VPC) . Crystallization from ethanol.water afforded a single crop of 3-(3' ,5' -di-t-butyl-4' -hydroxyphenyl)- 02,4-pentanedione (65%, overall yield, 97% pure). Example II A mixture of the N,N-dimethyl-2,6-di-t-butyl-4- aminomethylphenol (10.5g, 40 mmols), sodium hydroxide (1.8 g, 45 mmols) and acetylacetone (24 Ls, 10% 5 solution) was refluxed for 3 hours. Acetylacetone was distilled under reduced pressure to afford an oily residue of the 3-(3', 5' -di-t-butyl-4'-hydroxyphenyl)- 2,4-pentanedione compound (97% by VPC). Example III 0 A mixture of the N,N-dimethyl-2,6-di-t-butyl-4- aminomethylphenol (10.5g, 40 mmols), sodium hydroxide (3.6 g, 90 mmols) and acetylacetone (24 mLs, 10% solution) was refluxed for 3 hours. Acetylacetone was distilled under reduced pressure to afford an oily 5 residue of the 3-(3' ,5'-di-t-butyl-4'-hydroxyphenyl)- 2,4-pentanedione compound (377° by VPC).

Claims: - 13 - CLAIMS : 1. A process for the preparation of (3',5',- dihydrocarbyl-4' -hydroxybenzyl)-1,3-diketones which comprises reacting an N,N-dihydrocarbyl-2,6-dihydro- carbyl-4-aminomethylphenol with a 1,3-diketone in the presence of a basic substance. 2. A process as claimed in Claim 1 in which said (3' ,5' -dihydrocarbyl-4 * -hydroxybenzyl)-1,3-diketon has the general structural formula 0=C R_ and said N,N-dihydrocarbyl-2,6-dihydrocarbyl4-amino- methylphenol has the general structural formula M and said 1,3-diketone has the general structural formula R 5 C0CH 2 C0R 6 (II) in which in the above formula R, and R 2 are the same or different and are hydrogen or hydrocarbyl radicals having up to at least 40 carbon atoms with the provision that at least one of R-, or R 2 must be other than hydrogen, R« and R, are the same or different and are linear, branched or unbranched alkyl, aralkyl or cyclo¬ alkyl radicals having up to at least 20 carbon atoms, and Re and R. are the same or different and are linear or branched alkyl radicals having up to at least 20 carbon atoms. 3. The process as claimed in Claim 2 in which said basic substance is selected from the group consist- ing of an alkali metal hydroxide, an alkali metal salt of a weak acid, an alkaline earth metal hydroxide, an alkaline earth metal salt of a weak acid, amine bases or mixtures of the same. 4. The process as claimed in Claim 3 in which said basic substance is selected from the group consist¬ ing of sodium hydroxide, potassium hydroxide, barium hydroxide, rubidium hydroxide, cesium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, rubidium carbonate, potassium sulfite, sodium borate, potassium acetate, diazabicyclononane, pyridine, tetra- meth lguani'-tine and 1,4-diazabicyclo(2,2,2)-octane. 5. The process as claimed in Claim 1 in which said reaction is carried out at a temperature of from 50°C to 500°C. 6. The process as claimed in Claim 2 in which said reaction is carried out under pressure in the range of from atmospheric up to 1000 psig. 7. The process as claimed in Claim 2 in which said reaction is carried out in the presence of a sol¬ vent which is inert under the reaction conditions. 8. The process as claimed in Claim 7 in which the said solvent is an aprotic solvent. 9. The process as claimed in Claim 8 in which said aprotic solvent is a dipolar aprotic solvent is selected from dimethyl sulfoxide, N.N-dimethylfor amide, N,N-dimethylacetamide, dimethyl sulfone, tetramethylene sulfone, N-methylpyrrolidinone and acetonitrile. io. The process as claimed in Claim 7 in which said solvent is selected from the group consisting of low boiling hydrocarbons, halogenated hydrocarbons and lower alkanols having up to about 6 carbon atoms.

Inventors: EVERLY CHARLES RAY, ROPER JERRY MONROE, EVERLY, CHARLES, RAY, ROPER, JERRY, MONROE
Applicants: ETHYL CORP, ETHYL CORPORATION
Application year: 1983
Main classification: C07C45
IPC codes: B01J23, B01J27, B01J31, C07C45, C07C49, C07C67, F02B1