PROCESS FOR PREPARING SUBSTITUTED BENZYL MALONIC ACID ESTERS

Abstract: Esters of 3,5-dihydrocarbyl-4-hydroxybenzyl malonic acid are prepared by reacting a 2,6-dihydro-carbyl-4-hydrogen or -halogen substituted-methylphenol with an ester of a 1,3-dicarboxylic acid in the presence of an alkali metal hydride or an alkaline earth metal hydride. The products are useful as antioxidants.

Description: PROCESS FOR PREPARING SUBSTITUTED BENZYL MALONIC ACID ESTERS This invention relates to 3, 5-dihydrocarbyl-4- hydroxybenzylmalonic acid esters and the preparation and uses thereof as antioxidants for oxidizable organic materials when such materials are exposed to oxidative degradative conditions. The materials of the invention are prepared by reacting a 2, 6-dihydrocarbyl-4-substituted-methylphenol with an ester of a 1, 3-dicarboxylic acid in the presence of an alkali metal hydride or an alkaline earth metal hydride. Thus, in one embodiment of the invention there is provided a novel process for the preparation of 3, 5-dihydrocarbyl-4-hydroxybenzylmalonic acid esters which comprises reacting a 2, 6-dihydrocarbyl-4-hydroxy or -halogen substituted-methylphenol with an ester of a 1,3-dicarboxylic acid in the presence of an alkali metal hydride or an alkaline earth metal hydride. Thus, in the present invention there is provided a process for the preparation of 3, 5-dihydrocarbyl-4- hydroxybenzylmalonic acid esters having the general formula: OΛ * .PI which comprises reacting a 2,6-dihydrocarbyl-4-substi- tuted-methylphenol of the general formula: with an ester of a 1,3-dicarboxylic acid of the general formula: 0 0 II il R 3 0CCH 2 C0 4 in the presence of an alkali metal hydride or an alka¬ line earth metal hydride wherein in the structural for¬ mulas above R-, and R2 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 or branched al ' kyl radicals having up to at least 20 carbon atoms with the provision that at least one of R or R must be other than hydrogen and Y is hydroxy or halogen. 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 cycloheptyl radicals. Representative examples of the Group I compounds are 2,6-di-t-butyl-4-chloroe hylphenol, 2,6-di-t-butyl-4-bromomethylphenol, 2,6-di-t-butyl-4-iodomethylphenol, 2-meth l-6-isop opyl-4-chloromethylphenol, 2-methyl-6-isopropyl-4-bromometh lphenol, 2-meth 1-6-isoprop 1-4-iodomethylphenol, 2-me hyl-6- -buty1-4-chloromethylphenol, 2-methyl-6-t-butyl-4-bromomethylphenol, 2-meth 1-6-t-butyl-4-iodometh lphenol, 2,6-diisopropyl-4-chloroethylphenol, 2,6-diisopropyl-4-bromomethylphenol, 2,6-diisoprop l-4-iodomethylphenol, 2-sec-butyl-4-chloromethylphenol, 2-sec-butyl-4-bromomethylphenol, 2-sec-butyl-4-iodomethylphenol, 2-isopropyl-4-chloromethylphenol, 2-isopropyl-4-bromomethylphenol, 2-isopropyl-4-iodomethylphenol, 2-t-but 1-4-chloromethylphenol, 2-t-butyl-4-bromome hylphenol, 2-t-butyl-4-iodometh lphenol, 2-eth 1-6-t-butyl-4-chlorometh lphenol, 2-eth 1-6-t-buty1-4-bromomethylphenol, 2-eth 1-6-t-buty1-4-iodometh lphenol, 2,6-diheptyl-4-chloromethylphenol, 2,6-diheptyl-4-bromometh lphenol, 2,6-diheptyl-4-iodometh lphenol, 2-ethy1-6-methyl-4-chloromethylphenol, 2-eth l-6-methyl-4-bromomethylphenol, 2-eth l-6-methyl-4-iodomethylphenol, 2-t-buty1-6-heptyl-4-chloromethylphenol, 2-t-buty1-6-heptyl-4-bromomethylphenol, 2-t-but 1-6-heptyl-4-iodome hylphenol, 2-meth 1-6-ethy1-4-chloromethylphenol, 2-methyl-6-ethyl-4-bromomethylphenol, 2-me h 1-6-ethyl-4-iodomethylphenol, 2,6-di-t-but 1-4-hydroxymeth lphenol, 2-meth 1-6-isoproρyl-4-hydroxymeth lphenol, 2- eth 1-6-t-but 1-4-hydroxymethylphenol, 2, 6-diisoproρyl-4-hydroxymeth lphenol, 2-sec-butyl-4-hydroxymethylphenol, 2-isopropyl-4-hydroxymethylphenol, 2-t-buty1-4-hydroxymeth lphenol, 2-ethy1-6-t-bu yl-4-hydroxymethylphenol, 2, 6-diheptyl-4-hydroxymethylphenol, 2-eth 1-6-me hy1-4-hydroxymethylphenol, 2-t-buty1-6-heptyl-4-hydroxymethylphenol, 2-methy1-6-ethy1-4-hydroxyme h lphenol, and the like. Representative examples of Group II esters of arboxylic acid compounds are malonic acid, dimethyl ester, malonic acid, diethyl ester, malonic acid, diisopropyl ester, malonic acid, di-n-hexyl ester, malonic acid, dioctyl ester, ?ΛPI malonic acid, didodecyl ester, malonic acid, ethyl, methyl diester, malonic acid, ethyl, isopropyl diester, malonic acid, n-butyl, ethyl diester, malonic acid, n-butyl, dodecyl diester, malonic acid, octyl, ethyl diester, malonic acid, ethyl monoester, malonic acid, n-propyl monoester, malonic acid, n-butyl monoester, malonic acid, n-hexyl monoester, malonic acid, octyl monoester, malonic acid, dodecyl monoester, and the like. Representative examples of Group III benzylated malonic acid esters functioning as antioxidants, are 3,5-di-t-butyl-4-hydroxybenzylmalonic acid, dimethyl ester, 3,5-di-t-butyl-4-hydroxybenzylmalonic acid, diethyl ester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, diisopropyl ester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, di-n-hexyl ester, 3,5-di-t-butyl-4-hydroxybenzylmalonic acid, dioctyl ester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, didodecyl ester, --$\_ κ-.A U ____ 3,5-di-t-butyl-4-hydroxybenzylmalonic acid, ethyl, methyl* diester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, ethyl, isopropyl diester, 3,5-di-t-butyl-4-hydroxybenzylmalonic acid, n-butyl, ethyl diester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, n-butyl, dodecyl diester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, octyl, methyl diester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, octyl, ethyl diester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, ethyl monoester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, n-propyl monoester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, n-butyl monoester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, n-hexyl monoester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, octyl monoester, 3, 5-di-t-butyl-4-hydroxybenzylmalonic acid, dodecyl monoester, 3-ethyl-5-eth l-4-hydroxybenzylmalonic acid, dioctyl ester, 3-n-butyl-5-octyl-4-hydroxybenzylmalonic acid, ethyl, methyl- diester, 3-ethyl-5-methyl-4-hydroxybenzylmalonic acid, ethyl monoester, *-* 3,5-dioctyl-4-hydroxybenzylmalonic acid, octyl monoester, and the like. In general, any of the alkali metal hydrides or alkaline earth metal hydrides may be used in the prac¬ tice of the present process. These include sodium ■* *^ hydride, potassium hydride, lithium hydride, magnesium hydride, calcium hydride, and the like. Sodium hydride is preferred. The process of the invention is carried out by reacting the 2,6-dihydrocarbyl-4-hydroxymethylphenol or 15 the 2,6-dihydrocarbyl-4-halometh lphenol starting material with at least 1 molar equivalent of malonic acid ester reactant although an excess of ester reactant can be used. A preferred range of malonic acid ester reactant to halometh lphenol reactant or hydroxymethyl- 20phenol reactant is from about 1 to 10 moles of ester per mole of halomethylphenol or hydroxymethylphenol reactant. At least 1 mole of hydride per mole of halo- methylphenol or hydroxymethylphenol reactant should be used in the process of the invention, although an amount 2 of hydride up to about 50 moles of hydride per mole of the substituted methylphenol reactant can be used, if desired. 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 atmospheric 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 malonic acid ester 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-ethoxy- hexane, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, diglyme, 1,2-diethoxyethane, and tertiary amines such as pyridine, N-ethylpiperidine, triethylamine, tributyl- amine, N,N-diphenyl-N-methylamine, N,N-dimethylalanine, etc. Especially useful solvents are dipolar aprotic solvents such as dimethyl sulfoxide, N,N-dimethylforma- mide, N.N-dimethylacetamide, 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, 5 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, isopentyl alcohol, n-hexanol and isohexyl alcohol. The amount of solvent can be expressed as a volume ratio of solvent to halomethylphenol reactant or 5 hydroxymethylphenol reactant. Suitable volume ratios of solvent to halomethylphenol reactant or hydroxy¬ methylphenol 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 par- 2 ticularly critical. Accordingly, it is convenient to add the halomethylphenol reactant or the hydroxymethyl¬ phenol reactant to a mixture of the other materials, add the malonic acid ester compound to a mixture of the other materials, add the reactants to a mixture of the * - ■ -' substituted methylphenol and solvent, introduce all SREA ONIPL " 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 halo- 5 methylphenol reactant or the hydroxymeth lphenol to the corresponding benzylated malonic acid ester. 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 0 of the benzylated malonic acid ester 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 5 brought together and maintained under a substan- tially 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 0 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 conven¬ tional equipment. Under the reaction conditions, elimination of the hydroxyl group or halide occurs yielding a quinone _OMPl_ " V/Ir-O " ' methide intermediate which undergoes nucleophilic attack by the malonic acid ester -reactant to form the desired benzylated malonic acid ester product. Some bis - (hydroxyphenyl)methane and benzyl ether by-products may also be formed. The benzylated malonic acid ester product is easily separated from the reaction mixture by such means as distillation, extraction, crystallization and other methods obvious to those skilled in the chemical pro- cessing art. The benzylated malonic acid es ' ter products pre¬ pared by the process of this invention have antioxidant properties and are capable of stabilizing polymers nor¬ mally subject to oxidative degradation when incorporated 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 Sanbury. 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 example. Example I A dimethylformamide' solution (25 mmols) of , diethyl sodiomalonate (generated by treating a dimethyl¬ formamide solution of 2.4 g; 15 mmols diethyl alonate with 0.72 g; 30 mmols oil-free sodium hydride) was added with stirring under a nitrogen atmosphere to a dimethyl¬ formamide solution (25 Ls) of 2,6-di-t-butyl-4-chloro- methylphenol (2.49 g; 10 mmols). The reaction mixture was heated to a temperature of 125°C and held at that temperature for 3 hours and then poured into cold 2N hydrochloric acid (100 Ls) . The aqueous reaction slurry was extracted with diethyl ether (3 x 30 mLs). The combined organic extract was dried (MgSO^) and concentrated to give 2.44 g; 39% by VPC of 3,5-di-t- butyl-4-hydroxybenzylmalonic acid, diethyl ester. Example II To an ethanol solution (10 mLs) of 2,6-di-t- butyl-4-hydroxymethylphenol (2.63 g; 10 mmols) and ethanol solution (15 mmols) of diethyl sodiomalonate (generated by treating an ethanol solution of 1.6 g; 10 mmols diethyl malonate with 0.48 g; 20 mmols oil-free sodium hydride) was added with stirring under a nitrogen atmosphere. The reaction mixture was heated at reflux for 16 hours and then poured into cold 2N hydrochloric acid (100 mLs) . The aqueous reaction slurry was ex¬ tracted with diethyl ether (3 x 30 mLs). The combined organic extract was dried (MgSO,) and concentrated to give 1.42 g; 397o by VPC of.3,5-di-t-butyl-4-hydrox - benzylmalonic acid, ethyl ester.

Claims: CLAIMS 1. A process for the preparation of 3,5-di- hydrocarbyl-4-hydroxybenzylmalonic acid esters which comprises reacting a 2, 6-dihydrocarbyl-4-substituted- methylphenol with an ester of a 1,3-dicarboxylic acid in the presence of an alkali metal hydride or an alkaline earth metal hydride. 2. The process as claimed in Claim 1 in which the 3, 5-di-hydrocarbyl-4-hydroxybenzylmalonic acid esters has the general structural formula and the 2,6-dihydrocarbyl-4-substituted-methylphenol has the general structural formula and the ester of a 1,3-dicarboxylic acid of the general structural formula R 3 0CCH 2 C0R 4 (ID in which R, and R 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 Ro must be other than hydrogen, R and R, are the same or dif- ferent and are linear or branched alkyl radicals having up to at least 20 carbon atoms with the provision that at least one of Ro or R, must be other than hydrogen and Y is hydroxy or halogen. 3. The process of Claim 2 wherein said halogen is chlorine, bromine or iodine. 4. The process as claimed in Claim 2 in which said alkali metal hydride or alkaline earth metal hydride is selected from the group consisting of sodium hydride, barium hydride, lithium hydride, magnesium hydride and calcium hydride. 5. The process " as claimed in Claim 2 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 solvent 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 7 in which said aprotic solvent is a dipolar aprotic solvent selected from dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfone, tetramethylene sulfone, N-methylpyrrolidinone and acetonitrile. 10. 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 from 1 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: C07C67
IPC codes: B01J31, C07C67, C07C69