Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1998-02-26
1999-05-11
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
560 56, C07C51/10
Patent
active
059028980
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for preparing aralkanoic acids and, more particularly, relates to such a process employing a novel catalyst system.
BACKGROUND
As disclosed, e.g., in U.S. Pat. No. 4,694,100 (Shimizu et al.) and British Patent 1,565,235 (Mitsubishi), it is known that aralkenes, such as 4-isobutylstyrene, can be carboxylated with carbon monoxide and water or an alcohol in the presence of a palladium catalyst under acidic conditions to form an aralkanoic acid or ester, such as ibuprofen. Alperetal., J. Chem. Soc. Chem. Comm., 1983, pp. 1270-1271, disclose a similar reaction employing a mixture of palladium and copper and requiring the presence of oxygen; and European Patent Application 284,310 (Hoechst Celanese) teaches the use of a palladium catalyst in association with a phosphine ligand to accomplish the carboxylation of 1-(4-isobutylphenyl)ethanol to ibuprofen with carbon monoxide in an aqueous acidic medium.
These known processes have been used with some success. However, it would be desirable to develop a process that would not require the presence of oxygen or an acidic medium or the use of an uneconomical starting material like 1-(4-isobutylphenyl)ethanol but would still provide the acid or ester product in good yield.
SUMMARY OF THE INVENTION
It has been found that the activity of a palladium catalyst in the carboxylation of an aralkene with carbon monoxide and water or an alcohol in the absence of oxygen can be enhanced when it is used in conjunction with (A) a ligand mixture comprising compounds corresponding to the formulas R.sub.3 ZY and R'.sub.3 Z wherein each R and R' is independently selected from alkyl, aryl, and substituted aryl groups; Y is a member of Group VIA of the Periodic Table; and Z is an element having a Pauling electronegativity of 1.9-2.5 or (B) a complex ligand providing all of the elements of said mixture.
Thus, in the process of the invention, an aralkanoic acid or ester corresponding to the formula CH(R.sup.3)(R.sup.4)--C(R.sup.2)(Ar)--COOR.sup.1 is prepared by treating an aralkene having the formula C(R.sup.3)(R.sup.4).dbd.C(R.sup.2)Ar and a compound of the formula R.sup.1 OH with carbon monoxide at a temperature of 25-200.degree. C. and a pressure of at least .about.1 atmosphere (.about.0.1 MPa) in the absence of oxygen and in the presence of a palladium catalyst mixture containing a combination of R.sub.3 ZY and R'.sub.3 Z ligand elements; aryl, and substituted aryl groups; Y being a member of Group VIA of the Periodic Table; Z being an element having a Pauling electronegativity of 1.9-2.5; R.sup.1 being hydrogen or alkyl; R.sup.2, R.sup.3, and R.sup.4 being independently selected from hydrogen, alkyl, halo, trifluoromethyl, alkoxy, alkylthio, alkanoyl, cycloalkyl-substituted alkyl, cycloalkyl, substituted or unsubstituted aryl or heteroaryl, and substituted or unsubstituted aroyl or heteroarylcarbonyl groups; and Ar being substituted or unsubstituted aryl.
DETAILED DESCRIPTION
Aralkenes that may be carboxylated in the practice of the invention may be any of those indicated above.
Alkyl substituents in these compounds may have straight or branched chains and contain 1-20 carbons, such as methyl, ethyl, propyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, octyl, 2-ethylhexyl, 1,1,3,3-tetramethylbutyl, decyl, tetradecyl, eicosyl, etc., while cycloalkyl groups contain 3-7 carbons (e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl), and cycloalkyl-substituted alkyl groups have a cycloalkyl moiety of 3-7 carbons and a straight- or branched-chain alkyl moiety of 1-8 carbons, as in cyclopropylmethyl, cyclobutylmethyl, cycloheptylmethyl, 2-cyclopropylethyl, 2-cyclohexylethyl, 3-cyclopentylpropyl, 4-cyclopropylbutyl, 6-cyclohexylhexyl, and the like. When present, alkoxy and alkylthio substituents may be straight- or branched-chain groups containing 1-10 carbons (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, sec-butoxy, t-butoxy, hexyloxy, octyloxy, decyloxy, methylthio, ethylthio, propylthio, but
REFERENCES:
Samsel et al J. Am. Chem. Soc. 107, 7606-7617 (1985).
Irie et al Synlett, Apr. 1991 265-266.
Albemarle Corporation
Killos Paul J.
Pippenger Philip M.
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