Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus esters
Reexamination Certificate
2002-09-23
2004-06-08
Lambkin, Deborah C. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus esters
C560S008000
Reexamination Certificate
active
06747167
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a process for the preparation of acid esters, including phosphoric add esters and carboxylic acid esters from sterically hindered phenols and alcohols.
BACKGROUND OF THE INVENTION
It is known to use acid acceptors to drive reactions wherein one of the reactants is sterically hindered, e.g., a sterically hindered phenol or alcohol. Typical reactions involving sterically hindered reactants include the preparation of esters from acid chlorides such as acyl halides, phosphorous or chlorophosphous compositions, e.g., the reaction between benzoyl chloride and 2, 4, 6, tri-t-butylphenol to make an ester such as 2, 4, 6, tri-t-butyl benzoate, or the reactions between the appropriate hydroxy compounds and phosphorous compounds, e.g., phosphorous trihalides, to prepare organic diphosphites.
For example, in the preparation of organic diphosphites, the ease of substitution of the halides decreases as the halide is replaced. In the preparation of neoalkyl aryl phosphites, the neoalkyl diol readily reacts in essentially quantitative conversion with a phosphorous trihalide to yield a di-substituted neoalkyl halo phosphite (i.e., an intermediate di-substituted phosphorohalidite). The displacement of the third halo group is less than quantitative and is considerably slower in rate. Additionally, displacement of the third halo group by a sterically hindered phenol is even more difficult and requires elevated temperatures and/or use of a catalyst.
In order to increase the rate of reaction and the degree of completion for displacing the third halide with a sterically hindered moiety, various techniques have been generally utilized in the art. These techniques include elevating the reaction mixture temperature and the use of a basic catalyst or a hydrogen halide acceptor, e.g., amines. U.S. Pat. No. 5,786,497 discloses the use of a polymeric amine to increase the rate of reaction in the production of organic phosphites to about 97%. U.S. Pat. No. 5618,866 generally discloses that 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) can be used in a reaction to produce organic phosphites.
There is still a need for an improved method to increase the conversion yields in reactions wherein one of the reactants is sterically hindered.
SUMMARY OF THE INVENTION
The invention relates to a two-stage process for the preparation of acid esters from acid halides and sterically hindered phenols and alcohols, with the second stage of the process being carried out after obtaining a conversion rate of at least about 95%, in the presence of an acid acceptor selected from the group consisting of: 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 4-(dimethylamino)pyridine (DMAP), 1,4-diazabicyclo[2.2.2]octane (DABCO), or mixtures thereof, wherein the acid acceptor is present in an amount sufficient to drive the reaction to completion of at least 98%.
The invention also relates to the recovery of an acid acceptor selected from the group consisting of 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 4-(dimethylamino)pyridine (DMAP) or 1,4-diazabicyclo[2.2.2]octane (DABCO), from a process for preparing acid esters from a reaction in which one of the reactants is a sterically hindered compound.
In one embodiment of the invention, the acid halides are phosphorous compounds for the preparation of phosphoric acid esters, e.g., organic phosphites.
In another embodiment of the invention, the acid halides are acyl halides, e.g., benzoyl chloride, benzoyl bromide, trichloroacetyl chloride, methyl benzoyl chloride, etc., for the preparation of carboxylic acid esters such as benzoates, toluates, etc.
DETAILED DESCRIPTION OF THE INVENTION
As used within, “sterically hindered” means a characteristic of molecular structure in which the molecules have a spatial arrangement of their atoms such that a given reaction with another molecule is prevented or retarded in rate. A sterically hindered compound may be further defined as a compound having substitutents whose physical bulk does not require confinement within volumes insufficient for the exercise of their normal behavior as discussed in “Organic Chemistry,” D. J. Cram and G. Hammond, 2
nd
edition, McGraw-Hill Book Company, N.Y., page 215 (1964).
It is known that displacement of the third halo group in reactions with sterically hindered aliphatic or aromatic hydroxyl-containing compounds is quite difficult. The substitution rate of the reaction depends in part by the steric bulk of the hydroxyl-containing compounds.
Applicants have found that in the two-stage process of the present invention, after a conversion rate of 95% or more is achieved, the use of certain acid acceptors economically and surprisingly drive a reaction, in which one of the reactants is sterically hindered, to at least 98% completion to produce acid esters.
I. Reaction to produce Acid Esters. In one embodiment, acid esters are organic phosphites produced by reacting an acid halide such as a phosphorous halide with aliphatic or aromatic hydroxyl-containing compounds, wherein the halides are displaced by the hydroxyl-containing compounds.
Examples of organic phosphites include di-substituted phosphites or chlorophosphites. In one embodiment, the acid esters are diphosphites based upon pentaerythritol, wherein the phosphite esters are prepared from the reaction of an chlorophosphite obtained by reaction of phosphorous trihalide with pentaerythritol and further reaction with a hydroxyl-containing compound. The diphosphites containing alkyl, aryl, or alkyl-substituted aryl groups are especially desirable compounds due to their enhanced hydrolytic stability, ease of handling and compatibility with a wide variety of polymeric systems.
In another embodiment, the acid esters are organic phosphite esters having the formula P—(OR)
3
.
In another embodiment, the acid esters are phosphonites of the formula (RO)
2
P—R, wherein each R is independently selected from alkyl, aryl, alkaryl, aralkyl and substituted alkyl, aryl, alkaaryl and arakyl groups. Examples of organic phosphites include triphenyl phosphite, tris(2,5-di-tert-butylphenyl)phosphite, tris(2-tert-butylphenyl)phosphite, tris(2-phenylphenyl)phosphite, tris(2-(1,1-dimethylpropyl)phenyl)phosphite, tris(2-cyclohexylphenyl)phosphite, tris(2-tert-butyl4-phenylphenyl)phosphite, tris(2-tert-butyl-4-methylphenyi)phosphite, tris(2,4-di-tert-amylphenyl)phosphite, tris(2,4-di-tertbutylphenyl)phosphite and (2,4,6-tri-tert-butylphenyl)-2-butyl-2-ethyl-1,3-propanediol-phosphite.
In yet another embodiment, the acid esters are carboxylic acid esters. In one embodiment, the carboxylic acid esters are aromatic represented carboxylic acid esters by the general formula ARC(O)OH having between C
8
to C
40
total and produced by reacting a corresponding acyl halide with hydroxyl-containing compounds, wherein the halides are displaced by the hydroxyl-containing compounds. Examples of carboxylic acid esters include benzoates, toluates, anisates and the like.
Reactants—Acid Halides. In one embodiment, the acide halides are phosphorous halides PX
3
, the phosphorous halide compounds include chlorine, fluorine, bromine, iodine and mixtures thereof. Examples include phosphorous trichloride or phosphorous tribromide.
In one embodiment, the acid halides are di-substituted phosphites. For example, di-substituted phosphorohalidites of the general formula: wherein each of R1 and R2 are independently a C
1-20
alkyl, aryl, or alkaryl moiety and Y is a halogen.
In another embodiment, R1 and R2 are interconnected (i.e., the
residual of a diol) such that the di-substituted phosphite is a cyclic phosphite.
In yet one embodiment, the acid halides are phosphites based on butyl ethyl propanediol, e.g., 2-butyl-2-ethyl-1,3-propanediol-monochlorophosphite.
In another embodiment, the acid halides are acyl halides, which include the corresponding halides of the carboxylic acid esters, i.e., substituents derived from the corre
Enlow William Palmer
Gray Carloss La Verne
Prabhu Vaikunth Sitaram
Crompton Corporation
Dilworth Michael P.
Lambkin Deborah C.
Shameem Golam M M
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