JP2007524697A - Process for carbonylation of conjugated dienes - Google Patents

Abstract

(A) a palladium source; and (b) a bidentate diphosphine ligand of formula II:
R ¹ > P ¹ —R—P ² <R ² R ^{3 wherein} P ¹ and P ² represent a phosphorus atom; R ¹ is two optionally substituted tertiary carbon atoms Represents a divalent organic group linked to the phosphorus atom; and R ² and R ³ independently contain a tertiary carbon atom through which each group is linked to the phosphorus atom. Represents a monovalent group of 1 to 20 atoms, or R ² and R ³ together are optionally substituted at least two tertiary carbon atoms (through which The group is linked to the phosphorus atom); and R contains 3 atoms (through which P ¹ is linearly linked to P ² ). And (c) in the presence of a catalyst system comprising an anion source, the conjugated diene is converted to carbon monoxide and an active hydrogen source. A process for the carbonylation of conjugated dienes comprising reacting with a co-reactant having a child.

Description

  The present invention provides a process for the carbonylation of conjugated dienes.

The carbonylation reaction of conjugated dienes is well known in the art. In this application, the term carbonylation refers to the reaction of a conjugated diene catalyzed by a transition metal complex in the presence of carbon monoxide and a co-reactant. In this process, carbon monoxide as well as co-reactants are added to the diene, as described, for example, in WO-A-03 / 031457. WO-A-03 / 031457 includes (a) a palladium cation source, (b) a formula (I)
_{^{Q 1> P- (CH 2)}} n-PQ 2 Q 3 (I)
A phosphorus-containing ligand (wherein Q ¹ represents an unsubstituted or substituted 2-phospha-amadantan group or derivative thereof together with the phosphorus atom to which it is linked, wherein one or more of its carbon atoms are heteroatoms; Substituted divalent groups, Q ² and Q ³ independently represent a monovalent group having 1 to 20 atoms or together a divalent group having 2 to 20 atoms. N is 4 or 5) or a compound having a conjugated diene with carbon monoxide and an active hydrogen atom (eg hydrogen, water, alcohol and amine) in the presence of a catalyst system based on or a mixture thereof. Disclosed is a process for carbonylation of conjugated dienes that is reacted with.

  Under conditions normally used for carbonylation, for example, as described in WO-A-03 / 040065, conjugated dienes can also form dimers and / or short chain polymers. This side reaction is highly undesirable because it reduces the yield of the desired carbonylation product. Selectivity for carbonylation products over short chain polymerization products is further referred to herein as chemoselectivity.

  In addition to the need to achieve the highest possible chemical selectivity, it is also desirable to achieve a particularly high selectivity for one of several possible isomeric carbonylation products. Further referred to in the text as regioselectivity. For carbonylation of conjugated dienes, branched products usually have no industrial use, while linear products are important intermediates in the synthesis of adipic acid derivatives for use in, for example, polyamides. Therefore, regioselectivity for linear products, i.e. for reactions at primary carbon atoms, is often desired.

  The chemoselectivity and yield in the case of the catalyst disclosed in WO-A-03 / 031457 is low, requiring at least a relatively large amount of palladium and ligand to achieve a satisfactory turnover number, Must be hot. This adds to the cost of operating this disclosed process. Furthermore, the resulting product mixture is from the ligand residue (not required in industrial processes) due to low selectivity and from the by-products and due to the low stability of the ligand used. Considerable purification and / or separation is required.

  Therefore, it combines high chemoselectivity with high regioselectivity for linear carbonylation products, while at the same time using lower amounts of palladium for higher turnover and yield to improve the overall efficiency of the process There is still a need to provide a catalyst system which provides Such a combination also eliminates the need to subject the product mixture to substantial purification in order to remove short chain polymers and polymerization by-products and non-linear products.

  This time, the process for carbonylation of conjugated dienes shown above using a co-reactant having at least one active hydrogen atom is carried out very efficiently in the presence of a novel catalyst system as shown below. I found out that

Therefore, the present invention
(A) a palladium source; and (b) a bidentate diphosphine ligand of formula II,
^{R 1> P 1 -R-P} 2 <R 2 R 3 (II)
(Wherein P ¹ and P ² represent a phosphorus atom;
R ¹ represents a divalent organic group linked to the phosphorus atom by two optionally substituted tertiary carbon atoms; R ² and R ³ are independently a tertiary carbon atom ( Each represents a monovalent group of 1 to 20 atoms containing each group linked to the phosphorus atom, or R ² and R ³ together, optionally Forms a divalent organic group containing at least two tertiary carbon atoms through which the group is linked to the phosphorus atom; R is 3 atoms ( Via this, P ¹ is linearly linked to P ² ). And (c) a process for carbonylation of a conjugated diene comprising reacting the conjugated diene with carbon monoxide and a co-reactant having an active hydrogen atom in the presence of a catalyst system comprising an anion source. I will provide a.

  In the process according to the invention, suitable sources for palladium of component (a) include palladium metals and complexes and compounds thereof, palladium salts, such as, for example, palladium and salts of halogenated acids, nitric acid, sulfuric acid or sulfonic acids. Palladium complexes, for example complexes with carbon monoxide or acetylacetonate, or palladium combined with solid materials such as ion exchangers are included. Preferably, salts of palladium and carboxylic acids are used, suitably carboxylic acids having 12 or fewer carbon atoms, such as salts of acetic acid, propionic acid and butanoic acid, or substituted carboxylic acids (trichloroacetic acid and tricarboxylic acid). Salts of such as fluoroacetic acid. A very suitable source is palladium (II) acetate.

In the bidentate diphosphine ligand (b) according to formula (II), R ¹ represents an optionally substituted divalent organic group linked to the phosphorus atom by two tertiary carbon atoms; R ² and R ³ together or independently contain the same or different tertiary carbon atom (through which each group is linked to the phosphorus atom), optionally substituted organic Represents a group.

The groups R ¹ and R ² and R ³ independently or together may further contain one or more heteroatoms such as oxygen, nitrogen, sulfur or phosphorus and / or for example oxygen, nitrogen, sulfur And / or can be substituted with one or more functional groups, including halogens (eg fluorine, chlorine, bromine, iodine) and / or cyano groups.

R ¹ is a branched, heteroatom-unsubstituted or substituted divalent alkyl group having in each case 4 to 10 atoms in the alkylene chain, the CH ₂ group also representing, for example, —CO— , —O—, —SiR ₂ — or —NR— and the like, wherein one or more of the hydrogen atoms can be substituted with a substituent such as an aryl group.

Suitable monovalent groups R ² and R ³ are linked to each other only via the phosphorus atom P ² and preferably have 4 to 20 carbon atoms, even more preferably 4 to 8 carbon atoms. Has carbon atoms. The tertiary carbon atom through which each group is linked to a phosphorus atom can be substituted with an aliphatic, alicyclic or aromatic substituent, or a substituted saturated or unsaturated aliphatic ring structure All of which may contain heteroatoms. Preferably, the tertiary carbon atom is substituted with an alkyl group, so that the tertiary carbon atom becomes part of the tertiary alkyl group or is substituted with an ether group. Examples of particularly suitable organic groups R ² and R ³ are tert-butyl, 2- (2-methyl) -butyl, 2- (2-ethyl) butyl, 2- (2-phenyl) butyl, 2- (2 -Methyl) pentyl, 2- (2-ethyl) pentyl, 2- (2-methyl-4-phenyl) -pentyl and 1- (1-methyl) cyclohexyl groups.

The monovalent groups R ² and R ³ are each individually different organic groups, but in order to reduce the amount of different raw materials used in the synthesis, these groups preferably represent the same group. Even more preferably, R ² and R ³ represent a tert-butyl group because of the high steric hindrance induced by these groups and the high selectivity achieved with such ligands.

Very good results have been obtained with ligands where the groups R ² and R ³ represent the same monovalent tertiary alkyl group such as a tert-butyl group, but such ligands are Achieving an industrial scale can be difficult because of the use of metal organic compounds such as Grignard reactants.

With diphosphine ligands (R ¹ and R ² and R ³ together represent the same or different divalent groups linked directly to the phosphorus atom via two tertiary carbon atoms). Also very good results were obtained. The divalent group can have a monocyclic or polycyclic structure.

Thus, R ² together with R ³ is an optionally substituted divalent organic group linked to a phosphorus atom by two tertiary carbon atoms as defined above for R ¹ . Can be formed.

  Tertiary carbon atoms through which each group is linked to a phosphorus atom can be substituted by aliphatic, alicyclic and form part of a substituted saturated or unsaturated aliphatic ring structure, all of which are It can contain heteroatoms. Preferably, the tertiary carbon atom is substituted with an alkyl group so that the tertiary carbon atom becomes part of the tertiary alkyl group or is substituted with an ether group.

In suitable monovalent diphosphine structures, R ¹ and R ² and R ³ together represent an unsubstituted or substituted C ₄ -C ₃₀ alkylene group, wherein the CH ₂ group is a hetero, such as —O—. 1,1,4,4-tetramethyl-buta-1,4-diyl, 1,4-dimethyl-1,4-dimethoxy-buta-1,4-diyl, 1,1, which can be substituted by a group 5,5-tetramethyl-penta-1,5-diyl-, 1,5-dimethyl-1,5-dimethoxy-penta-1,5-diyl-, 3-oxa-1,5-dimethoxy-penta-1 , 5-diyl-, 3-oxa-1,1,5,5-tetramethyl-penta-1,5-diyl, 3-oxa-1,5-dimethyl-1,5-dimethoxy-penta-1, 5-diyl- and similar having two tertiary carbon atoms linked to a phosphorus atom The thing containing the bivalent group structure of these is included.

Diphosphines containing such divalent groups have the advantage of being available via various synthetic routes, including reacting phosphines under mild conditions, thereby making them more obtainable on an industrial scale. It becomes easy. Thus, R ¹ and R ² and R ³ can also together represent an optionally substituted divalent alicyclic group, which is connected via two tertiary carbon atoms. Linked to the phosphorus atom. R ² together with R ¹ and R ³ is in this case preferably a branched, heteroatom-unsubstituted or substituted divalent alkyl group having 4 to 10 atoms in its alkylene chain, The CH ₂ group can also be substituted with a hetero group such as —CO—, —O—, —SiR ₂ — or —NR—, and one or more of the hydrogen atoms are substituted with a substituent such as an aryl group, for example. Can be done.

Of these, particularly preferred R ¹ , optionally a divalent monocyclic structure together with R ² and R ³ , such as 2,2,6,6-tetrasubstituted phosphinan-4-one or 2,2,6, A 6-tetrasubstituted phosphinane-4-thione structure, whose ring atoms can be optionally substituted by heteroatoms. Ligands containing such structures can conveniently be obtained under mild conditions as described in WO 02/064249.

For example, a bidentate diphosphine having the same organic group R ¹ , and R ² and R ³ together, conveniently converts the compound H ₂ P ¹ —R—P ² H ₂ (A) to the compound (Z ¹ Z ² C) = (CZ ³ )-(C = Y)-(CZ ⁴ ) = (CZ ⁵ Z ⁶ ) (B) (wherein Z ¹ , Z ² , Z ⁵ and Z ⁶ are optionally heterogeneous. Represents an organic group substituted with an atom, Z ³ and Z ⁴ optionally represent an organic group or a hydrogen group substituted with a heteroatom, and Y represents oxygen or sulfur. Can be.

An example for such a compound is 2,6-dimethyl-2,5-heptadien-4-one (also known as diisopropylideneacetone or phorone). When more than one compound (B) is used, ligands with different groups containing R ¹ and R ² and containing R ³ and R ⁴ are formed. This bidentate ligand can be prepared in the meso and rac forms. For the purposes of the present invention, mesotypes are preferred.

In the diphosphine ligand according to formula (II), R preferably represents a divalent bridging group containing three atoms through which P ¹ is linearly linked to P ² . For those skilled in the art, the term “linearly linked” clearly and clearly means that the phosphorus atoms P ¹ and P ² are linearly and directly linked by a three atom chain. . For example, when R is a trimethylene group, the ligand is
_{^{R 1> P 1 -Ch 2 -CH}} 2 -CH 2 -P 2 <R 2 R 3
It has the following structure.

Suitable bridging groups R can be optionally substituted, such as trimethylene (n-propane), based on carbon atoms and / or derivatives thereof, such as those carbon atoms such as in oxydimethane or in dimethylamine. One or more of is replaced by a heteroatom. Suitable heteroatoms include nitrogen, sulfur, silicon or oxygen atoms. Thus, the bridging group R can be substituted, for example with an alkyl group or a heteroatom, or can be unsubstituted. Suitable substituents for the bridging group include groups containing heteroatoms such as halides, sulfur, phosphorus, oxygen and nitrogen. Examples of such groups include chloride, bromide, iodide and the general formulas —O—H, —O—X ₂ , —CO—X ₂ , —CO—O—X ₂ , —S—H, — S—X, —CO—S—X, —NH ₂ , —NHX, —NO ₂ , —CN, —CO—NH ₂ , —CO—NHX and —CO—NX ₂ (wherein X is independently Represents alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl and n-butyl. However, R preferably represents trimethylene (n-propane) because such ligands can be used easily.

Particularly preferred diphosphine ligands according to the present invention are compounds according to formula (II) (wherein, ^{R 1} and, ^{R 2} together with ^{R 3} together with the respective phosphorus atom ^{P 1} or ^{P 2,} 2 , 2,6,6-tetra-substituted phosphinan-4-one, and R represents a propylene (trimethylene) skeleton structure.

  The molar ratio of bidentate diphosphine (ie catalyst component (b)) per mole atom of palladium (ie catalyst component (a)) is not critical. Preferably it is in the range of 0.1 to 100, more preferably 0.5 to 10, even more preferably 1 to 5, even more preferably 1 to 3, and even more preferably 1 to 2, even more preferably. Is in the range of 1 to 1.5. In the presence of oxygen, it is beneficial to be slightly higher than the stoichiometric amount.

Very surprisingly, a similar ligand (R is ethylene) having a tertiary butyl or cyclic substituent at the phosphorus atom is more active than the ligand according to the process of the present invention. It turned out to be very limited. Similarly, a ligand disclosed in WO-A-03 / 031457 (wherein R ¹ to R ⁴ are as defined herein, but R represents more than 3 atoms. Having (especially 4 or 5) bridging groups) is very low activity and requires a larger amount of palladium to achieve the same level of conversion (approximately 1: 450 for diene substituents). ), It must be hotter and the selectivity is very low. Thus, in the process of the present invention, preferably the catalyst is present in an amount of no more than 500 mole atoms of palladium per mole of conjugated diene.

  This process allows conjugated dienes to react with carbon monoxide and co-reactants. The conjugated diene reactant has at least 4 atoms. Preferably the diene has from 4 to 20, more preferably from 4 to 14 carbon atoms. However, in various preferred embodiments, the process can also be applied to molecules containing conjugated double bonds in their molecular structure (eg, in the chain of a polymer such as a synthetic rubber).

  The conjugated diene can be substituted or unsubstituted. Preferably, the conjugated diene is an unsubstituted diene. Examples of useful conjugated dienes are 1,3-butadiene, conjugated pentadiene, conjugated hexadiene, cyclopentadiene and cyclohexadiene, all of which can be substituted. Of particular commercial interest are 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene).

  The feed containing the diene reactant need not necessarily be free of alkene contamination because the carbonylation reaction of the present invention is particularly selective for the diene feed. In the feed, up to 5 mol% of alkynes based on the diene reactant can be tolerated.

  The ratio of diene and co-reactant in the feed (v / v) can vary widely, suitably in the range of 1: 0.1 to 1: 500.

The co-reactant according to the present invention can be any compound having a mobile hydrogen atom and capable of reacting with the diene under a catalyst as a nucleophile. The nature of the co-reactant generally determines the type of product formed. Suitable co-reactants are water, carboxylic acids, alcohols, ammonia or amines, thiols or combinations thereof. When the co-reactant is water, the resulting product is an ethylenically unsaturated carboxylic acid. An ethylenically unsaturated anhydride is obtained when the co-reactant is a carboxylic acid. In the case of alcohol co-reactants, the carbonylation product is an ester. Similarly, the use of ammonia (NH ₃ ) or primary or secondary amines RNH ₂ or R′R ″ NH produces an amide, and the use of thiol RSH produces a thioester. , R, R ′ and / or R ″ optionally represents a heteroatom-substituted organic group, preferably an alkyl, alkenyl or aryl group. When ammonia or amines are used, a small amount of these co-reactants react with the acid present in the formation of amides and water. Therefore, water is always present in the case of ammonia or amine co-reactants.

  Preferably, the carboxylic acid co-reactant has the same number of carbon atoms as the diene reactant plus one.

  Preferred alcohol co-reactants have alkanols having 1 to 20, more preferably 1 to 6 carbon atoms per molecule and 2 to 20, more preferably 2 to 6 carbon atoms per molecule. Alkanediol. The alkanol can be aliphatic, alicyclic or aromatic. Suitable alkanols in the process of the present invention include methanol, ethanol, ethanediol, n-propanol, 1,3-propanediol, iso-propanol, 1-butanol, 2-butanol (sec butanol), 2-methyl-1 -Propanol (isobutanol), 2-methyl-2-propanol (tert-butanol), 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1- Butanol (isoamyl alcohol), 2-methyl-2-butanol (tert-amyl alcohol), 1-hexanol, 2-hexanol, 4-methyl-2-pentanol, 3,3-dimethyl-2-butanol, 1 -Heptanol, 1-octanol, 1-nonanol, 1-decano , 1,2-ethylene glycol and 1,3-propylene but glycol include, can achieve high turnover, since the resulting product is particularly useful, these, methanol is most preferred.

  Preferred amines have 1 to 20, more preferably 1 to 6 carbon atoms per molecule, and diamines have 2 to 20, more preferably 2 to 6 carbon atoms per molecule. Have. The amine can be aliphatic, alicyclic or aromatic. More preferred are ammonia and primary amines in order to achieve high turnover. When the anion (c) of the catalyst system is an acid, preferably the amount of ammonia or amine is less than the stoichiometry based on the amine functionality.

  For some reason, if the co-reactant is ammonia and a small amount of a primary amine, the small amount of acid present reacts with the amide under the liberation of water. There is therefore always a small amount of acid formed from conjugated dienes, carbon monoxide and water, which in turn replaces the acid that is converted to the amide by direct reaction as described above.

  The thiol co-reactant can be aliphatic, alicyclic or aromatic. Preferred thiol co-reactants are aliphatic thiols having 1 to 20 carbon atoms, more preferably 1 to 6 carbon atoms per molecule, 2 to 20, more preferably 2 to 6 per molecule. It is an aliphatic dithiol having 1 carbon atom.

  The anion source (c) is preferably an acid, more preferably a carboxylic acid, which can serve as both the promoter (c) as well as the solvent for the reaction.

  Even more preferably, the anion source is an acid having a pKa greater than 2.0 (measured in an aqueous solution at 18 ° C.), and more preferably the catalyst component (c) is from 3.0 An acid having a large pKa, more preferably an acid having a pKa greater than 3.6.

  Examples of preferred acids include carboxylic acids such as acetic acid, propionic acid, butyric acid, pentanoic acid, pentenoic acid and nonanoic acid, and the latter three acids have low polarity and high pKa, so the catalyst It is highly preferred because it has been found to improve the activity of the system. Very conveniently, the acid corresponding to the desired product of the reaction can be used as catalyst component (c).

  Pentenoic acid is particularly preferred when the conjugated diene is 1,3-butadiene. The catalyst component (c) can also be an ion exchange resin containing carboxylic acid groups. This advantageously simplifies the purification of the product mixture.

The molar ratio of the anion and palladium sources, ie catalyst components (c) and (b), is not critical. However, as it increases the activity of the catalyst system, it is suitably between 2: 1 and 10 ⁷ : 1, more preferably between 10 ² : 1 and 10 ⁶ : 1 and even more preferably 10 ^2. Between 1: 1 and 10 ⁵ : 1 and most preferably between 10 ² : 1 and 10 ⁴ : 1.

  If the co-reactant is to react with an acid that acts as a source of anions, the amount of that acid relative to the co-reactant should be selected so that an appropriate amount of free acid is present. In general, a large amount of excess acid over the co-reactant is preferred to increase the reaction rate.

The amount by which the complete catalyst system is used is not critical and can vary within wide limits. Usually, per mole of the conjugated diene, palladium, an amount ranging from ^{10 -8} to ^{10 -1,} preferably used in an amount ranging from ^{10 -7} to ^{10 -2} mole atom, preferably per mole, 10 ^- It is in the range of ⁵ to 10 ^-2 gram atoms. The process can optionally be carried out in the presence of a solvent, but preferably an acid acting as component (c) is used as solvent and promoter.

  The carbonylation reaction according to the invention is carried out at moderate temperatures and pressures. Suitable reaction temperatures are in the range of 0 to 250 ° C, more preferably in the range of 50 to 200 ° C, and even more preferably in the range of 80 to 150 ° C.

  The reaction pressure is usually at least atmospheric pressure. Suitable pressures are in the range of 0.1 to 15 MPa (1 to 150 bar), preferably in the range of 0.5 to 8.5 MPa (5 to 85 bar). A carbon monoxide partial pressure in the range of 0.1 to 8 MPa (1 to 80 bar) is preferred, and an upper range of 4 to 8 MPa is more preferred. Higher pressures require special equipment preparation.

  In the process according to the invention, carbon monoxide may be used with carbon monoxide alone or diluted with an inert gas such as nitrogen, carbon dioxide or a rare gas such as argon, or a co-reactant gas such as ammonia. it can.

  Furthermore, the addition of a limited amount of hydrogen, such as 3 to 20 mol% of the amount of carbon monoxide used, promotes the carbonylation reaction. However, using larger amounts of hydrogen tends to cause unnecessary hydrogenation of diene reactants and / or unsaturated carboxylic acid products.

  The invention is illustrated by the following non-limiting examples.

(Example 1 and Comparative Examples A to D)
Batch reaction for butadiene carbonylation with methanol.

  In a 250 ml magnetic stirring autoclave, palladium acetate (0.1 mmol), 20 ml methanol, 40 ml pentenoic acid and 0.3 mmol of each ligand in Example 1 and Comparative Examples A and B and Comparative Examples C and D 0.5 mmol of the ligand used in was subsequently added.

  The autoclave was then closed, evacuated, flushed with nitrogen, and then 20 ml butadiene was pumped. The autoclave was pressurized with CO to 6.0 MPa, sealed, heated to 135 ° C. and maintained at that temperature for 10 hours. Finally, the autoclave was cooled and the reaction mixture was analyzed by GLC.

  As shown in Table I, the initial carbonylation rate (mol / mol Pd / hour) of this batch operation is defined as the average rate of CO consumption over the first 2 hours.

  In Example 1, about 80% of the butadiene was converted with a selectivity to methylpentenoate of greater than 95%. In Comparative Examples A and B, about 30% of the butadiene reacted with a mixture of 4-vinylcyclohexene and butadiene polymer. In Comparative Examples C and D, CO conversion could not be measured.

  This result shows that the process exhibits surprisingly high conversion and selectivity in the claimed catalyst system, while the performance of ligands that are not according to the invention but are structurally closely related. It turned out to be inferior.

Claims (9)

(C) a palladium source; and (d) a bidentate diphosphine ligand of formula II,
^{R 1> P 1 -R-P} 2 <R 2 R 3 (II)
Wherein P ¹ and P ² represent a phosphorus atom; R ¹ represents a divalent organic group linked to the phosphorus atom by two optionally substituted tertiary carbon atoms; R ² and R ³ independently represent a monovalent group of 1 to 20 atoms containing a tertiary carbon atom through which each group is linked to the phosphorus atom. Or R ² and R ³ together are optionally substituted two containing at least two tertiary carbon atoms through which the group is linked to the phosphorus atom. Forming a valent organic group; R represents a divalent bridging group comprising 3 atoms (through which P ¹ is linearly linked to P ² ); and (c) an anion source Reacting a conjugated diene with carbon monoxide and a co-reactant having an active hydrogen atom in the presence of a catalyst system comprising Process for the carbonylation of conjugated dienes.   The process of claim 1, wherein R is an optionally substituted trimethylene group. R ¹ and / or R ² and R ³ together form a 2,2,6,6-tetra-substituted phosphinan-4-one structure or a 2,2,6,6-tetra-substituted phosphinan-4-thione structure. 3. A process according to claim 1 or claim 2 representing.   The process according to any one of claims 1 to 3, wherein the anion source (c) is a carboxylic acid.   The process according to any one of claims 1 to 4, wherein an amount of 3 to 20 mol% hydrogen is added to carbon monoxide.   The process according to any one of claims 1 to 5, wherein the conjugated diene is 1,3-butadiene or 2-methyl-1,3-butadiene. The process according to any one of claims 1 to 6, wherein the catalyst component (c) is present in a molar ratio in the range of 10 ² : 1 and 10 ⁴ : 1 to the catalyst component (a). .   The reaction temperature is in the range of 50 to 250 ° C, the reaction pressure is in the range of 0.1 to 15 MPa, and the partial pressure of carbon monoxide is in the range of 0.1 to 6.5 MPa. A process according to any one of claims 1 to 7.   9. The process according to any one of claims 1 to 8, wherein the catalyst component is present in an amount of no more than 500 mole atoms of palladium per mole of conjugated diene.