Process for the selective preparation of alkenecarboxylic acid derivatives

A process for the selective carbonylation of a conjugated diene by contacting with carbon monoxide in the presence of a hydroxyl-group-containing compound such as water, alcohol, phenol or carboxylic acid in liquid phase using a catalyst system formed by the combination of: PA1 (a) a palladium compound and PA1 (b) at least one organic bidentate phosphine.

FIELD OF THE INVENTION 
The invention relates to a process for the preparation of alkenecarboxylic 
acid derivatives by carbonylation of conjugated dienes, in particular to 
the preparation of 3-pentenoic acid and higher homologues from 
1,3-butadiene and higher conjugated dienes. The Invention also includes a 
novel catalyst containing palladium and multidentate phosphine suitable 
for said carbonylation process. 
BACKGROUND OF THE INVENTION 
Processes for the carbonylation of olefinically unsaturated hydrocarbons 
are known from British Patent Specification No. 1,110,405 and from U.S. 
Pat. Nos. 4,172,087 and 4,414,409 inter alia. 
In the British Patent Specification No. 1,110,405 published Apr. 18, 1968, 
a process is described for the preparation of esters by the reaction of a 
diene with carbon monoxide and an alcohol or phenol in the presence of a 
catalyst containing platinum and/or palladium and/or nickel, and/either 
(a) bromide and/or iodide ions or 
(b) 
(i) a ligand that is able to form a coordination linkage with the metal 
component of the catalyst and that contains nitrogen, phosphorus, arsenic 
or sulfur, preference being given to trivalent phosphorus-containing 
ligands, and particular preference to a primary, secondary or tertiary 
phosphine or an alkyl, aryl or cycloalkyl phosphite and 
(ii) chloride, bromide or iodide. 
Although the conversion of butadiene is mentioned as one of the 
embodiments, preference is clearly given on page 2, lines 97-103, to 
dienes as starting compounds, wherein the double bonds are separated by 2, 
3 or 4 single bonds. Moreover, the presence of bromide, iodide or chloride 
is considered to be essential. The reaction is preferred slightly to be 
performed in an acidified reaction medium by, for example, the presence of 
toluenesulfonic acid therein. 
From the yields of pent-3-enoate obtained in the relevant examples, it will 
be clear to a person skilled in the art that the aforesaid British patent 
specification certainly does not provide this expert with any indications 
for the very selective preparation of pent-3-enoate and higher homologues 
from 1,3-butadiene and higher conjugated dienes. 
From U.S. Pat. No. 4,172,087, issued Oct. 13, 1979, a process is known for 
the simultaneous preparation of two groups of unsaturated carboxylic acids 
and esters thereof from aliphatically conjugated diene starting materials 
containing from 4 to 8 carbon atoms, wherein: 
(a) every two moles of the aliphatically conjugated diene concerned are 
mixed with a three-component mixture consisting of 
(i) at least a catalytic quantity of a palladium catalyst consisting of 
either one or more palladium halides in combination with one or more 
tertiary-phosphorus-containing monodentate donor ligands or one or more 
halide-free palladium salts in combination with one or more 
tertiary-phosphorus-containing multidentate donor ligands. 
(ii) at least one molar equivalent of a hydroxyl-group-containing 
co-reactant selected from the group consisting of water or an aliphatic 
alcohol containing 1 to 12 carbon atoms, and 
(iii) an (N-heterocyclic) amine base; 
(b) the reaction mixture is pressurized with sufficient carbon monoxide to 
satisfy the stoichiometry of the carbonylation reaction; 
(c) the pressurized reaction mixture is heated until substantial formation 
of the desired aliphatic carboxylic acid derivatives has been achieved; 
and 
(d) the unsaturated carboxylic acid derivatives concerned that occur 
therein are isolated. 
Although the conversion of 1,3-butadiene and aliphatically conjugated diene 
is mentioned, the presence of an N-heterocyclic base, such as pyridine, 
alkylated pyridines, quinoline, lutidine, picoline, isoquinoline, 
alkylated quinolines and isoquinolines, acridine and 
N-methyl-2-pyrrolidone or N,N-dimethylaniline, N,N-diethylaniline, 
N,N-diethyltoluidine, N,N-dibutyl-toluidine and N,N-dimethylformamide, is 
considered to be an essential precondition. 
In particular, from the yields of pent-3-enoate mentioned in the described 
examples, it will be clear to an expert that the process according to the 
aforesaid U.S. Pat. No. 4,172,087 certainly gives no indications for a 
very selective preparation of pent-3-enoate and higher homologues from 
1,3-butadiene and higher conjugated dienes. 
From the U.S. Pat. No. 4,414,409, issued Nov. 8, 1983, a carbonylation 
process is known for the preparation of acids and esters by conversion of 
an olefinically unsaturated compound, carbon monoxide and a hydroxyl 
compound at about 50.degree. C. to about 150.degree. C., in the presence 
of a catalyst consisting of an organic phosphine ligand palladium complex 
and a perfluorosulfonic acid. 
A clear preference is, moreover, indicated in column 2, lines 26-29, and in 
column 9, line 27, for the conversion of non-conjugated hydrocarbons. 
It will be clear that the processes described hereinbefore are either 
unsuitable for the conversion of conjugated unsaturated compounds or, in 
particular, do not seem to be suited to a very selective preparation of 
3-pentenoic acid or derivatives and higher homologues, and that those 
skilled in the art, searching for improved selective preparation methods 
for 3-pentenoic acid and derivatives thereof, which are becoming an 
increasingly important starting material for organic syntheses (for 
example, for the preparation of adipic acid and derivatives thereof), have 
been diverted away from the methods described hereinbefore. 
More in general, a number of known processes have the disadvantage that 
they use relatively high concentrations of the relevant catalyst system 
and also use aggressive reaction components, for example, acids such as 
hydrohalogenic acids or salts thereof and other rigorous reaction 
conditions, which necessitate cost-increasing measures in connection with 
safety and the apparatus life (corrosion). 
An object of the present invention, therefore, is to provide an improved 
very selective carbonylation of 1,3-butadiene and higher homologues to 
very valuable products, such as 3-pentenoic acid or derivatives thereof. 
Another object of the present invention is to provide a novel catalytic 
system for said carbonylation process formed by combining a palladium 
compound with bidentate phosphine(s). 
SUMMARY OF THE INVENTION 
An improved process has now been found for the selective conversion of 
conjugated dienes such as 1,3-butadiene, 1,3-hexadiene and 2,4-heptadiene 
in liquid phase to the aforesaid compounds with a generally increased 
conversion rate, in the presence of a characteristic catalyst system and 
without the presence of (N-heterocyclic) amines and/or halides, whereby 
cheaper types of steel can be used for the reactor installations. 
The invention therefore provides a process for the selective carbonylation 
of conjugated dienes in the presence of a hydroxyl-group-containing 
compound such as water, alcohol, phenol or carboxylic acid, in liquid 
phase and in the presence of a specific catalyst system substantially free 
of organic nitrogen-containing base that can be formed by combination of 
(a) a palladium compound and 
(b) at least one multidentate organic phosphorus ligand. 
In particular, the aforesaid process is accomplished in the presence of a 
catalyst system that can be formed by the combination of 
(a) a palladium compound and 
(b) at least one bidentate phosphine derivative with the general formula: 
EQU R.sub.1 R.sub.2 &gt;P--R--P&lt;R.sub.3 R.sub.4 (I) 
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 each represent individually a 
hydrocarbon group and R represents a divalent organic bridge group with at 
least 2 carbon atoms in the bridge. In particular, the groups R.sub.1 and 
R.sub.3 represent individually an aryl group, preferably phenyl or 
naphthyl, the groups R.sub.2 and R.sub.4 represent individually an alkyl 
group of 1-20 carbon atoms and preferably 2-6 carbon atoms, a cycloalkyl 
group or an aryl group, and the group R represents an alkylene group of 
2-6 carbon atoms, a phenylene or cycloalkylene group. 
DETAILED DESCRIPTION OF THE INVENTION 
The bidentate phosphine derivative has the following general formula: 
EQU R.sub.1 R.sub.2 &gt;P--R--P&lt;R.sub.3 R.sub.4 (I) 
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 represent individually a 
hydrocarbon group and R represents a divalent organic bridge group with at 
least 2 carbon atoms in the bridge. In particular, the groups R.sub.1 and 
R.sub.3 represent individually an aryl group, preferably phenyl or 
naphthyl, the groups R.sub.2 and R.sub.4 represent individually an alkyl 
group of 1-20 carbon atoms and preferably 2-6 carbon atoms, a cycloalkyl 
group or an aryl group, and the group R represents an alkylene group of 
2-6 carbon atoms, a phenylene or cycloalkylene group. 
As used herein, the term "hydrocarbon group" shall include unsubstituted 
hydrocarbon group as well as hydrocarbon group bearing one or more 
substituents selected from the group consisting of alkyl of 1-4 carbon 
atoms, alkoxy of 1-4 carbon atoms and halogen. Said halogen is preferably 
fluorine or chlorine. 
The terms "aryl group," "alkyl group," "cycloalkyl group," "alkylene group" 
and "phenyl group" as used hereinafter shall include substituted as well 
as unsubstituted group(s) and the substituent(s) must be one which would 
not adversely affect the carbonylation reaction when the bidentate 
phosphine is used for the catalysis of said reaction. 
According to a preferred embodiment, it is possible, depending on the 
chosen other catalyst components, to add a catalytic quantity of a 
protonic acid with a pKa value &gt;3 to increase the yield of, for example, 
pentenoates, in the case of conversion of butadiene at approximately 
constant high selectivity. The selectivity of, for example, 3-pentenoic 
acid or derivatives thereof, expressed as a percentage, is defined as: 
##EQU1## 
where "a" is the quantity of 1,3-butadiene converted into 3-pentenoic acid 
or derivatives thereof, and "b" the total quantity of converted 
1,3-butadiene. 
It will be clear that the very high selectivity that has been found for the 
conversion of, for example, 1,3-butadiene into 3-pentenoic acid and 
derivatives thereof is achieved at the cost of the coincidental formation 
of 3,8-nonadienic acid or the derivatives thereof, 4-vinyl-1-cyclohexene 
and 1,3,7-octatriene as in the known earlier process. 
Examples of particularly suitable phosphorus ligands are: 
1,2-di(diphenylphosphino) ethane, 
1,3-di(diphenylphosphino) propane, 
1,4-di(diphenylphosphino) butane, 
1,5-di(diphenylphosphino) pentane, 
1,6-di(diphenylphosphino) hexane, 
1,2-tetrafluorocyclobutene diyl bis diphenyl phosphine, 
1,2-phenylene bis diphenyl phosphine, 
1,2-ethane diyl bis(ditrifluoromethyl) phosphine, 
1,3-propane diyl bis(ditrifluoromethyl) phosphine, 
1,3-propane diyl bis(trifluoromethyl phenyl) phosphine, 
1,2-hexafluorocyclopentene diyl bis diphenyl phosphine, 
1,2-tetrafluorocyclobutene diyl bis diphenyl phosphine, 
1,2-octafluorocyclohexene diyl bis diphenyl phosphine, 
1,4-diphenyl-1,4-diphosphacyclohexane or mixtures thereof. 
Very good results are obtained with 1,4-di(diphenylphosphino) butane, 
1,3-di(diphenylphosphino) propane and 1,5-di(diphenylphosphino) pentane or 
mixtures thereof. Moreover, it has been found that good relative 
conversion results can be obtained if, in addition to the multidentate and 
preferably bidentate phosphine ligands that are in any case present in the 
said catalyst system, one or more monodentate phosphine ligands are also 
present. A particularly preferred group of these last-mentioned compounds 
includes the group represented by the general formula: 
##STR1## 
wherein R.sub.6 represents an aryl group and preferably a phenyl or 
naphthyl group and R.sub.7 and R.sub.8 each represent (i) individually an 
alkyl, cycloalkyl or aryl group; or (ii) R.sub.7 and R.sub.8 together 
represent an alkylene or phosphacyclo-alkylene group. Mixtures of these 
phosphines can also be employed. Preferably, each alkyl group herein 
contains up to 20 carbon atoms, each cycloalkyl group up to 7 carbon atoms 
in the ring and each aryl group up to 18 carbon atoms in the ring. An aryl 
group can represent an anthryl, naphthyl or phenyl group. Phosphines 
according to Formula II, in which R.sub.6 and R.sub.7 each represent a 
phenyl group, form a preferred group. Within this group the phosphines, in 
which R.sub.8 also represents a phenyl group, form a particularly 
preferred group. 
The protonic acids with pKa value &gt;3, which may be added to the catalyst 
system, preferably consist of benzoic acid or benzoic acids substituted 
with one or more electron-repelling groups such as 2,4,6-trimethyl benzoic 
acid, and para-hydroxybenzoic acid. 
Both homogeneous and heterogeneous palladium catalyst components can be 
used for the selective conversion according to the invention. However, 
homogeneous catalyst systems are preferred. Suitable homogeneous catalyst 
components are formed by salts of palladium with, for example, nitric 
acid, sulfuric acid or alkane carboxylic acids containing not more than 12 
carbons atoms. Of these, palladium (II) acetate is preferred, however, 
palladium complexes, such as palladium acetylacetonate, 
o-toluylphosphine-palladium acetate or bistriphenylphosphinepalladium 
sulfate can be employed. Palladium linked to an ion exchanger, such as an 
ion exchanger containing sulfonic acid groups, is an example of a suitable 
heterogeneous catalyst component. The quantity of palladium is not 
critical. If a divalent palladium compound is used, preference is given to 
the use of quantities in the range of between 10.sup.-5 and 10.sup.-1 gram 
atoms of palladium per mole of conjugated dienes and preferably butadiene. 
It has been found that for the best results the molar ratio of the organic 
phosphorus compound relative to palladium should not be greater than 10 
moles phosphine per gram atom of palladium. Very high selectivities and 
very high conversion rates are achieved if the molar ratio of the 
phosphine to palladium is between 2 and 5 mole per gram atom of palladium 
(e.g., 100% conversion of butadiene in 5 hours at 150.degree. C.). It has 
been found that the proportion of the--possibly added--protonic acid with 
pKa value &gt;3 should preferably be 6-10 equivalents of acid per gram atom 
of palladium. 
A separate solvent is not essential for the process according to the 
invention, and often an excess of one of the reactants or products will 
form a suitable liquid phase. In some cases, however, it may be desirable 
to use a separate solvent. Any inert solvent can, in principle, be used 
for this purpose. This can, for example be chosen from sulfoxides and 
sulfones, for example, dimethyl sulfoxide, diisopropyl sulfone or 
tetrahydrothiophene 1,1-dioxide (also called sulfolane), 2-methyl-4-butyl 
sulfolane, 3-methyl sulfolane; aromatic hydrocarbons such as benzene, 
toluene, xylenes; esters such as methyl acetate and butyrolactone; ketones 
such as acetone or methyl isobutyl ketone; and ethers such as anisole, 
2,5,8-trioxanone (also referred to as diglyme), diphenyl ether and 
diisopropyl ether or mixtures thereof. Preferably, diphenyl ether is 
employed. 
The process according to the invention enables relatively mild reaction 
conditions to be used. Temperatures of from 50.degree. C. to 150.degree. 
C. and more in particular from 20.degree. C. to 100.degree. C. have been 
found to be very suitable. 
The initial pressure of the carbon monoxide can vary over a wide range, but 
will in general be lower than that of hitherto know processes. Pressures 
of from 25 to 65 bar are preferred. 
In the process according to the invention, the carbon monoxide can be used 
in its pure form or diluted with an inert gas such as nitrogen, rare gases 
or carbon dioxide. In general, the presence of more than 5% hydrogen is 
undesirable, since this can cause hydrogenation of the conjugated diene 
under the reaction conditions. 
The molar ratio of the alcohol, phenol, water or carboxylic acid relative 
to the conjugated diene, in particular butadiene, can vary between wide 
limits and generally lies in the range of 0.1:1 to 10:1. 
According to a preferred embodiment of the process of the invention, an 
alcohol can be employed as hydroxyl-containing reactant. The alcohol can 
be aliphatic, cycloaliphatic or aromatic and can, if necessary, carry one 
or more inert substituents. A suitable alcohol can contain up to 20 carbon 
atoms, one or more hydroxyl groups can be present, in which case different 
products may be formed. For example, a polyvalent alcohol, in particular 
lower sugars such as glucose, fractose, mannose, galactose, sucrose, 
aldoxose, aldopentose, altrose, talose, gulose, idose, ribose, arabinose, 
xylose, lyxose, erythrose or threose, can be reacted with a suitable 
quantity of butadiene to form a monoester or a polyvalent ester. The 
choice of the alcohol will therefore only depend on the desired product. 
Alkanols such as methanol, ethanol, propanol or 
2,2-dihydroxymethyl-1-butanol and alcohols containing ether bridges, such 
as triethylene glycol, all give valuable products. 
According to another embodiment of the process of the invention, a great 
variety of carboxylic acids can be used as reactant. For example, the 
carboxylic acids can be aliphatic, cycloaliphatic or aromatic and may 
possible carry inert substituents. Suitable carboxylic acids contain a 
maximum of 25 carbon atoms. The carboxylic acids used as reactant are 
preferably alkane carboxylic acids or alkene carboxylic acids. Examples of 
suitable carboxylic acids are formic acid, acetic acid, propionic acid, 
n-butyric acid, isobutyric acid, pivalic acid, n-valeric acid, n-caproic 
acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic 
acid, stearic acid, phthalic acid and teraphthalic acid. Examples of 
alkene carboxylic acids are acrylic acid, propiolic acid, methacrylic 
acid, crotonic acid, isocrotonic acid, oleic acid, maleic acid, fumaric 
acid, citraconic acid and mesaconic acid. 
The process according to the invention can in principle also be employed 
with polyvalent carboxylic acids, whereby, depending on the chosen 
reaction conditions, including the molar ratio of the reactants employed, 
a variety of products can be obtained as required. If an alkane carboxylic 
acid is converted according to the process of the invention with 
1,3-butadiene, a symmetrical or a composite anhydride can be formed. 
Preferably, weak acids are employed for the process according to the 
invention, with pKa &gt;3 measured in an aqueous medium at 18.degree. C. 
Even more preference is given to the employment of acids that cannot be 
esterified, or only with difficulty, in connection with losses during the 
process. 
The process according to the invention has been found to be particularly 
suitable for continuous processes, e.g., repeated use of the relevant 
catalyst system, which offers great advantage for use on an industrial 
scale. 
It will be clear that another aspect of the present invention is formed by 
the aforesaid catalyst systems, which are used for the selective 
conversion of conjugated dienes, as such or in the form of a solution in 
one or more of the suitable, aforesaid solvents. 
The ranges and limitations provided in the instant specification and claims 
are those which are believed to particularly point out and distinctly 
claim the instant invention. It is, however, understood that other ranges 
and limitations that perform substantially the same function in 
substantially the same manner to obtain the same or substantially the same 
result are intended to be within the scope of the instant invention as 
defined by the instant specification and claims.

The invention will now be explained with reference to the following 
examples, without the invention being thereby limited to these 
embodiments: 
EXAMPLE 1 
A 300 ml magnetically stirred HASTELLOY C.RTM. autoclave was successively 
filled with 15 ml ethanol, 40 ml diphenyl ether, 1 mmole palladium acetate 
and 5 mmole 1,4-di(diphenylphosphino) butane. The autoclave was 
vacuum-evacuated, whereupon 8 ml of butadiene and carbon monoxide were 
added to an initial carbon monoxide pressure of 60 bar. The autoclave was 
heated to 155.degree. C. After a reaction time of 5 hours, the contents of 
the autoclave were analyzed by means of gas-liquid chromatography. The 
selectivity of the butadiene to pentenoate conversion was found to be 95%, 
while the pentenoate yield was 30%, calculated on the starting quantity of 
butadiene. 
EXAMPLE 2 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with a catalyst system composed of palladium acetate (1 
mmole) and 1,3-di(diphenylphosphino) propane (1.5 mmole). The selectivity 
of the butadiene to pentenoate conversion was found to be 92%, while the 
pentenoate yield, calculated on the starting quantity of butadiene, was 
50%. 
EXAMPLE 3 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with a catalyst system composed of 1 mmole palladium 
acetate, 2 mmole 1,4-di(diphenylphosphino) butane and 5 mmole triphenyl 
phosphine. The selectivity found for the butadiene to pentenoate 
conversion was 93%, while the pentenoate yield, calculated on the starting 
quantity of butadiene, was found to be 50%. 
EXAMPLE 4 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with the aid of a catalyst system composed of 1 mmole 
palladium acetate, 4 mmole 1,4-di(diphenyl-phosphino) butane and 7.5 mmole 
2,4,6-trimethyl benzoic acid. The reaction temperature was 150.degree. C. 
and the reaction time was 2.5 hours. The selectivity of the butadiene to 
pentenoate conversion was found to be 96%, while the pentenoate yield, 
calculated on the starting quantity of butadiene, was 90%. 
EXAMPLE 5 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with the aid of a catalyst system composed of 1 mmole 
palladium acetate, 2 mmole 1,4-di(diphenylphosphino) butane, 4 mmole 
triphenyl phosphine and 7.5 mmole 2,4,6-trimethyl benzoic acid. The 
reaction temperature was 150.degree. C. and the reaction time was 2.5 
hours. The selectivity of the butadiene to pentenoate conversion was found 
to be 91%, while the pentenoate yield, calculated on the starting quantity 
of butadiene, was found to be 88%. 
EXAMPLE 6 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with the aid of a catalyst system composed of 1 mmole 
palladium acetate, 4 mmole 1,4-di(diphenylphosphino) butane and 7.5 mmole 
2,4,6-trimethyl benzoic acid. The initial pressure of the carbon monoxide 
was 30 bar. The reaction temperature was 150.degree. C. and the reaction 
time was 2.5 hours. The selectivity of the butadiene to pentenoate 
conversion was 90%, while the pentenoate yield, calculated on the starting 
quantity of butadiene, was found to be 89%. 
EXAMPLE 7 (FOR COMISON) 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with the aid of a catalyst system composed of 1 mmole 
palladium acetate, 10 mmole triphenyl phosphine and 7.5 mmole 
2,4,6-trimethyl benzoic acid. The reaction temperature was 150.degree. C. 
and the reaction time was 2.5 hours. The selectivity found for the 
butadiene to pentenoate conversion was 75% (15% of the butadiene was found 
to have been converted into nonadienoates) and the pentenoate yield, 
calculated on the starting quantity of butadiene, was 55%. 
EXAMPLE 8 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with the aid of a catalyst system composed of 1 mmole 
palladium acetate and 1.5 mmole 1,2-di(diphenylphosphino) ethane. The 
selectivity found for the butadiene to pentenoate conversion was 88%, 
while the pentenoate yield, calculated on the starting quantity of 
butadiene, was 40%. 
EXAMPLE 9 
In a virtually analogous manner as described in Example 1, an experiment 
was performed with the aid of a catalyst system composed of 1 mmole 
palladium acetate and 4 mmole 1,2,4-di(diphenylphosphino) butane and 7.5 
mmole 2,4,6-trimethyl benzoic acid. During the reaction time of 10 hours, 
additional ethanol and butadiene was added at dosing rates of 25 mmole 
ethanol/hour and 25 mmole butadiene/hour. The selectivity found for the 
butadiene to pentenoate conversion was 90%, while the pentenoate yield, 
calculated on the starting quantity of butadiene was 81%.