CA1199937A - Process for preparing 2-(3',5-dihydrocarbyl-4'- hydroxybenzyl)-1,3-diketones - Google Patents

Abstract

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

Description

Case 5015 ~2 -PROCESS FOR PREPARING1(3',5'~DIHYDROCARBYL-4'-HYD~OXYBENZYL.)-l,~-DIKETONES
~,',~
This invention relates to novel and eminently useful (3'j5'-dihydrocarbyl-4'-hydroxybenzyl)-1,3-diketones and the preparation and uses thereof as anti-oxidants Eor oxidizable organic materials when such materials are exposed to oxidative degradative condi-tions.
The materials of the invention are prepa~ed by reacting an N~N-dihydrocarbyl-2,6-dihydrocarbyl-4-amino-methylphenol with a 1~3-diketone and a basic material~
preferably selected from alkali metal hydroxidesl 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 t3',5'-dihyd~ocarbyl-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'-~' 3'7 dihydrocarbyl-4'-hydroxybenzyl)-1,3-diketones which comprises reacting an N,N-dihydrocarbyl-2,6-dihydro-carbyl-4-aminomethylphenol with a 1,3-diketone and a basic material selected from the group consisting of 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 a process for the preparation of (3',5'-dihydrocarbyl-4'-hydroxybenzyl)-1,3-diketones having the general formula OH
Rl~ R2 1 (III) H2C ~ C~

O= C ~

which comprises reacting an N~N-dihydrocarbyl-2l6-di-20 hydrocarbyl-4-aminomethylphenol oE the general Eormula OH
Rl~ R2 (I) C ~ / R3 N

~R4 ~993~

with a 1,3-diketone of the cJeneral formula R5COCH~COR~

in the presence of a basic substance wherein in ~he structural formulas above Rl and R2 are the same or different and are hydrogen or hydrocarbyl radicals having up to at leas-t 40 carbon atoms with the provision tha~
at least one of Rl or R~ must be other than hydrogen;
R3 and R4 are the same or different and are linear, branched or unbranched alkyl, aralkyl or cycloalkyl radicals having up to at least 20 carbon atoms; or R3 and R4 together ~ith the N to which they are attached form a piperidine, morpholine or pyrrolidine ring; and R5 and R6 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-dimethyl-2,6-di-t-butyl-4-aminomethvlphellol, mab/ ~

:~g9~37 N,N-dimethyl,2-methyl-6-isopropyl-4-amino-me-thylphenol I
N,N-dimethyl,2-methyl-6-t-butyl-4-amlno-methylphenol, N,N-dimethyl,2,6-dii~opropyl-4-aminomethyl-phenol, N,N-dimethyl,2-sec-butyl-4-aminomethylphenol, N~N-dimethyl,2-isopropyl-4-aminomethylphenol, N,N-dimethyl,2-t-butyl 4-aminomethylphenol, 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-methyl,2-methyl-6-ethyl-4-amino-methylphenol, 3,5-di-t-butyl-4-hydroxybenzylpiperidine, 3~5-di-t-butyl-4-hydroxybenzylmorpholinel and 2S 3,5-di-t-butyl-4-hydroxybenÆylpyrrolidine.

~ ~ g ~ ~ 3 ~

Representative examples of Group II l,3-di-carbonyl compounds are

2,4-pentanedione, 2,4-heptanedione, 4,6-nonanedione, 2,6-dimethyl-3,5-heptanedione, l-hexyl-1,3-butanedione, l-hexyl-2,4-pentanedione, and 1,3~dihexyl-1,3-propanedione.
Representative examples of Group III benzylated 1,3-diketone compounds, functioning as antioxidants, are

3-(3',5'-di.-t-butyl-4'-hydroxybenzyl)-2,4-pentanedionej 3-(3'-met~yl-5'-isopropyl-4'-hydroxybenzyl)-2,4--pentanedione, 3-(3'-methyl-5'-t-butyl-4'-hydroxybenzyl)-2,4-pentanedione, 3-(3',5'-diisopropyl-4'-hydroxybenzyl)-2,4-pentanedione, 3-(3'-sec-buty1-4'-hydroxybenzyl)-2,4-pentane-dione, 3-(3'-isopropyl-4'-hydroxybenzyl)-2,4-pentane-dione, 3-(3l-t-butyl-4'-hydroxybenzyl)-2,4-pentane-dione, ~ :
:: 5 _ :

~ 3 ~

3-(3'-ethyl-5'-methyl-4'-hydroxybenzyl)-2~4-heptanedione~
5-(3'j5'-dioctyl-4'-hydroxybenzyl)-4~6-nonanedione~

4-(3'-t-butyl-5'-heptyl-4'-hydroxybenzyl)-2J6-dimethyl-3~5-heptanedione~
2-(3',5'-dioctyl-4'-hydroxybenzyl)-l-hexyl-l~3-butanedione~
3-(3'~5'-dioctyl-4'-hydroxybenzyl)-l-hexyl-2~4-pent~nedione~ and 2-(3'~5'-dioctyl-4'-hydroxybenzyl)-1~3-dihexyl-l,3-propanedione.
In general~ the basic reactant of the instant process may be any of the alkali metal or alkaline earth 15 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/ po~assium carbonate, cesium 20 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 25 reacting the benzylamine starting ma-terial with at least l molar equivalent of ~-diketone reactant and l molar 993~

equivalent of base although an excess of either or both diketone and basic reactant can be used. A preferred range of ~-diketone reactant to benzylamine reactant is from 1 to 10 moles oE ~-diketone per mole of benzyl-

5 amine. A preferred range of basic reactant to benzyl-amine reactant ranges Erom 1 to 10 moles oE base per mole of benzylamine. It should be statedl however ! that the use of increasing amounts of basic material in the process tends to decrease the yield of desired 10 benzylated 1~3-diketone product.
The reaction is advantageously conducted at a temperature of Erom 50C. to 500C. While lower temperatures can be used ! the reaction rates are generally correspondingly lower. Temperatures above 15 500C. 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~ ~igher pressures up to about 20 lO00 psig may be used~ if desired.
The use oE a solvent for the reaction ~i~ture 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 ~ 3 7 such as diethyl ether, dibutyl ether~ l~ethoxyhexane, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, diglyme, 1,2-diethoxyethane, and tertiary amines such as pyridine, N-ethylpiperidine, triethylamine, tributyl-5 amine, N,N-diphenyl-N-meLhylamine, ~,N-dimethylalanine, etc. Especially useful solvents are dipolar aprotic solvents such as dimethyl sulfoxide, NIN-dimethylforma-mide, N,N-dimethylacetamide, dimethyl sulfone, tetra-methylene sulfone, N-methylpyrrolidinone, acetonitrile 10 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-et~ane, the chlorina~ed benzenes, the chlorinated 15 toluenes, etc., and lower alkanols having up to about 6 carbon atoms. These include, methanol, ethanol, n-pro-panol, isopropyl alcoholl n-butanol, sec-butyl alcohol, t-butyl alcohol, n-pentanol, isopentyl alcohol~
n-hexanol and isohexyl alcohol.
The amount of solvent can be expressad as a volume ratio of solvent to benzylamine reactant.
Suitable volume ratios of solvent to benzylamine reactant can be from 0/1 to 500/l and preferably from l/l 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 materials, add the 1,3-dicarbonyl compound to a mixture of the other materials, add the basic reactant to a mixture of tbe other materials, add the reactants to a mixture of the benzylamine and solvent, introduce all 5 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 1,3-10 diketone. The length of time for optimum yield willdepend 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 15 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 20 dry~ inert atmosphere. By "substantially anhyd~ous" is meant a reaction system wherein the total amount oE
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 25 of product decrease~

3 ~, `

The process may readily be conducted in a batch-wise, semi-batch or contlnuous manner and in -conventional equipment.
The process of the invention when run continous-5 ly can be illustrated schematically by the equation shown below. Rl, R2, R3, R4, R5 and R6 are the same radicals as descrihed and exemplified above.

OH

~ ~ ~ Rscocll2coR6 se H C ~ 3 2. ~ N

OH

,~
~ O
2 C C ~
2~ I R
O=C 5 Under the reaction conditions, the benzylamine reactant is alky].ated to initially yield a quaternary ammonium salt of the benzylamine which subsequently 25 eliminates a tertiary amine component from the salt to ~ 10 -~ .
~3 ~ 3 ~

produce a quinone methide intermediate which undergoes nucleophilic attack by the 1,3-diketone reactant to form the desired benzylated 1,3-diketone product. During the course of the reaction some bis(hydroxyphenyl)methane 5 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 10 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 oE stabilizing polymers normally subject to oxidative degradation when incor-lS porated into the polymers using conventional techniquessuch as by addition to polymer lattices; or by addition to solid polymers on a mill or in a Banbury. ~urther~
the novel compounds of this invention are effective antioxidants in both unleaded and leaded gasolines made 20 from a wide variety of base stocks and for engine and industrial oils which are derived Erom crude petroleum or produced synthetically.
The practice of this invention will be still ~rther apparent by the ollowing illustrative examples.

9 ~ 3 ~

Example I
A mixture of N,N-dimethyl-2j6-di t-butyl-4-aminomethyl-phenol (2.63 g, 10 mmols)~ sodium hydroxide (0.6 g~ 15 mmols) and acetylacetone (24 mmols~ 10%
5 solution) was refluxed for 3 hours in a glass reaction vessel. Acetylacetone was distilled under reduced pressure to afford an oily residue containing 3-(3'~5'-di-t-butyl 4'-hydroxyphenyl)-2J4-pentanedione (80% by VPC). Crystalli~ation from ethanol:water afforded a 10 single crop of 3-(3'~5'-di-t-butyl-4'-hydroxyphenyl)-2,4-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 mLs~ 10~/o 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).
Examp:le III
A mixture of the N~N-dimethyl-2~6-di-t butyl-4-aminomethylphenol (10.5g~ 40 mmols)~ sodium hydroxide (3.6 g~ ~0 mmols) and acetylacetone (24 mLs~ 10/o solution) was refluxed for 3 hours. Acetylacetone was 25 distilled under reduced pressure to afford an oily residue of the 3-(3'~5'-di-t-butyl-4'-hydroxyphenyl)-2~4-pentanedione compound (37% by VPC).

Claims (30)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of a compound having the general structural formula (III) which comprises reacting a compound of the general structural formula (I) with a 1,3-diketone of the general formula R5COCH2COR6 (II) in the presence of a basic substance selected from 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, an amine base and a mixture thereof;
wherein R1 and R2, independently, represent a group selected from H and a hvydrocarbyl radical having up to at least 40 carbon atoms, with the proviso that R1 and R2 do not both represent 11;

R3 and R4, independently, represent a group selected from a linear and branched alkyl, aralkyl and cycloalkyl radical having up to at least 20 carbon atoms; or R3 and R4, when taken together with the N to which they are attached, form a ring selected from piperidine, morpholine and pyrrolidine;
and R5 and R6, independently, represent a group selected from a linear and branched alkyl radical having up to at least 20 carbon atoms.

2. The process of claim 1, wherein the com-pound of general structural formula (I) is selected from the group consisting of: N,N-dimethyl-2,6-di-t-butyl-4-aminomethylphenol, N,N-dimethyl-2-methyl-6-isopropyl-4-aminomethylphenol, N,N-dimethyl-2-methyl-6-t-butyl-4-aminomethylphenol, N,N-dimethyl-2,6-diisopropyl-4-amino-methylphenol, N,N-dimethyl-2-sec-butvl-4-aminomethyl-phenol, N,N-dimethyl-2-isopropyl-4-aminomethylphenol, N,N-dimethyl-2-t-butyl-4-aminomethylphenol, 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-aminomethylphenol, N,N-dioctyl-2,6-diheptyl-4-aminomethyl-phenol, N,N-dioctyl-2-ethyl-6-methyl-4-aminomethylphenol, N,N-di-octyl-2-t-butyl-6-heptyl-4-aminomethylphenol, N-ethyl-N-methyl-2,6-di-t-butyl-4-aminomethylphenol, N-octyl-N-methyl-2-methyl-6-ethyl-4-aminomethylphenol, 3,5-di-t-butyl-4-hydroxybenzylpiperidine, 3,5-di-t-butyl-4-hydroxy-benzylmorpholine and 3,5-di-t-butyl-4-hydroxybenzyl-pyrrolidine.

3. The process of claim 1, wherein the compound of general formula (II) is selected from the group consisting of: 2,4-pentanedione, 2,4-heptanedione, 4,6-nonanedione, 2,6-dimethyl-3,5-heptanedione, 1-hexyl-1,3-butanedione, 1-hexyl-2,4-pentanedione and 1,3-dihexyl-1,3-propanedione.

4. The process of claim 1, wherein said basic substance is selected from the group consisting 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, tetramethylguanidine and 1,4-diazabicyclo(2,2,2)-octane.

5. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 and R2 represent t-butyl and for the compound of general formula (II), R5 and R6 represent methyl, to produce 3-(3',5'-di-t-butyl-4'-hydroxybenzyl)-2,4-pentanedione.

6. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 represents methyl and R2 represents isopropyl and for the compound of general formula (II), R5 and R6 represent methyl, to produce 3-(3'-methyl-5'-isopropyl-4'-hydroxy-benzyl)-2,4-pentanedione.

7. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 represents methyl and R2 represents t-butyl and for the compound of general formula (II), R5 and R6 represent methyl, to produce 3-(3'-methyl-5' t-butyl-4'-hydroxy-benzyl)-2,4-pentanedione.

8. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 and R2 represent isopropyl and for the compound of general formula (II), R5 and R6 represent methyl, to produce 3-(3',5'-diisopropyl-4'-hydroxybenzyl)-2,4-pentanedione.

9. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 represents sec-butyl and R2 represents II and for the compound of general formula (II), R5 and R6 represent methyl, to produce 3-(3'-sec-butyl-4-hydroxybenzyl)-2,4-pentanedione.

10. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 represents isopropyl and R2 represents H and for the compound of general formula (II), R5 and R6 represent methyl, to produce 3-(3'-isopropyl-4'-hydroxybenzyl)-2,4-pentanedione.

11. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 represents t-butyl and R2 represents II and for the compound of general formula (II), R5 and R6 represent methyl, to produce 3-(3'-t-butyl-4'-hydroxybenzyl)-2,4-pentanedione.

12. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 represents ethyl and R2 represents methyl and for the compound of general formula (II), R5 represents methyl and R6 represents propyl, to produce 3-(3'-ethyl-5'-methyl-4'-hydroxybenzyl)-2,4-heptanedione.

13. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 and R2 represent octyl and for the compound of general formula (II), R5 and R6 represent propyl, to produce 5-(3',5'-dioctyl-4'-hydroxybenzyl)-4,6 nonanedione.

14. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 represents t-butyl and R2 represents heptyl and for the compound of general formula (II), R5 and R6 represent isopropyl, to produce 4-(3'-t butyl-5'-heptyl-4'-hydroxy-benzyl)-2,6-dimethyl-3,5-heptanedione.

15. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 and R2 represent octyl and for the compound of general formula (II), R5 represents hexyl and R6 represents methyl, to produce 2-(3',5'-dioctyl-4'-hydroxybenzyl)-1-hexyl-1,3-butanedione.

16. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 and R2 represent octyl and for the compound of general formula (II), R5 represents -CH2-hexyl and R6 represents ethyl, to produce 3-(3',5'-dioctyl-4'-hydroxybenzyl)-1-hexyl-2,4-pentanedione.

17. The process defined in claim 1, wherein for the compound of general structural formula (I), R1 and R2 represent octyl and for the compound of general formula (II), R5 and R6 represent hexyl, to produce 2-(3',5'-dloctyl-4'-hydroxybenzyl)-1,3-dihexyl-1,3-propanedione.

18. The process of claim 1, wherein the molar ratio of said 1,3-diketone reactant to the benzylamine derivative reactant is from about 1 to 10 moles of 1,3-diketone per mole of benzylamine derivative.

19. The process of claim 1, wherein the molar ratio of said basic substance reactant to the benzylamine derivative reactant is from about 1 to 10 moles of basic sub-stance per mole of benzylamine derivative.

20. The process of claim 1, wherein said reaction is conducted at elevated temperature.

21. The process of claim 20, wherein said reaction is carried out at a temperature of from about 50°C to about 500°C.

22. The process of claim 1, wherein said reaction is carried out under pressure in the range of from about atmospheric up to about 1,000 psig.

23. The process of claim 1, wherein said reaction is carried out at a temperature in the range of from about 50°C to about 500°C and under pressure in the range of from about atmospheric to about 1,000 psig.

24. The process of claim 1, wherein said reaction is carried out in the presence of a solvent which is inert under the reaction conditions.

25. The process of claim 24, wherein said solvent is an aprotic solvent.

26. The process of claim 24, wherein said aprotic solvent is a dipolar aprotic solvent.

27. The process of claim 26, wherein said dipolar aprotic solvent is selected from: dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfone, tetramethylene sulfone, N-methylpyrrolidinone and acetonitrile.

28. The process of claim 24, wherein said solvent is selected from the group consisting of low boiling hydrocarbons, halogenated hydrocarbons and C1-6 alkanols.

29. The process of claim 24, wherein the volume ratio of said solvent to the benzylamine derivative reactant is from about 0/1 to about 500/1.

30. The process of claim 1, wherein the reaction is carried out under a substantially dry inert atmosphere.