Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2003-08-25
2004-12-28
Killos, Paul J. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C562S522000, C502S155000
Reexamination Certificate
active
06835850
ABSTRACT:
The invention relates to a process for the carbonylation of a conjugated diene by reacting the conjugated diene with carbon monoxide and an hydroxyl group containing compound in the presence of a catalyst system comprising (a) a source of palladium cations, (b) a diphosphine ligand, and (c) a source of anions. In particular it relates to the preparation of alkyl pentenoates and/or adipates from 1,3-butadiene and derivatives thereof.
A carbonylation reaction means every reaction between a non-saturated substrate, an hydroxyl group containing compound and carbon monoxide.
U.S. Pat. No. 5,495,041 describes a process for the preparation of a pentenoate ester by carbonylation of butadiene in the presence of carbon monoxide, alcohol and a catalyst system comprising palladium, pentenoic acid and a phosphine ligand. The phosphine ligand can be a monodentate or multidentate phosphine ligand or a mixture thereof. As possible bidentate phosphine ligands 2,3-dimethyl-1,4-bis(diphenylphospino)butane, 2,3-bis(diphenylphospino)-2-butene, 1,3 bis(diphenylphosphino)-2-oxopropane and 1,2-bis(diphenylphosphino)cyclohexane are mentioned. A disadvantage of the process as described in U.S. Pat. No. 5,495,041 is that the catalyst system has only a moderate activity.
An object of the present invention is to provide an improved process in terms of catalyst activity for carbonylation of conjugated dienes.
This object is achieved in that the diphosphine ligand is a ligand having the general formula I
X
1
—R—X
2
(I)
wherein X
1
and X
2
represent a cyclic group with at least 5 ring atoms, of which one is a phosphorus atom, and R represents a bivalent aliphatic bridging group, connecting both phosphorus atoms, containing from 2 to 4 atoms in the bridge, which is substituted with at least one substituent or R represents a phenyl group with both phosphorus groups bound to the 1,2-position.
It has surprisingly been found that when such a process is carried out with such a specific choice of diphosphine ligand unexpected advantages with regard to the catalyst activity are obtained.
Another advantage is that the catalyst system remains stable over a prolonged period of time and can be reused several times without loss or without substantial loss of catalyst activity.
WO-A-0056695 describes a process for the preparation of mono- and diesters by reaction of a conjugated diene, with carbon monoxide and an hydroxyl group containing compound in the presence of a catalyst system including a source of palladium cations, a diphosphine ligand and a source of anions. As a possible diphosphine ligand 1,2-P,P′-bis(9-phosphabicyclononyl)propane is mentioned. Although acceptable catalyst activity is obtained, there is still room for further improvement. Also this known catalyst system leaves room for improvement regarding stability. The process of the present invention is specifically directed to the carbonylation of conjugated dienes, which show specific reaction characteristics when compared to ethylenically unsaturated compounds in general. Conjugated dienes contain at least two conjugated double bonds in the molecule. By conjugation is meant that the location of the &pgr;-orbital is such that it can overlap other orbitals in the molecule. Thus, the effects of compounds with at least two conjugated double bonds are often different in several ways from those of ethylenically unsaturated compounds with no conjugated double bonds. It is generally acknowledged that the carbonylation of conjugated dienes comprises more difficulties than that of an ethylenically unsaturated compound with no conjugated double bonds. In contrast to ethylenically unsaturated compounds with no conjugated double bonds, carbonylation of conjugated dienes involves Pd-&pgr;-allyl intermediate species, which are relatively stable against carbon-monoxide insertion reactions.
The bridging group R of the diphosphine ligand represents a bivalent aliphatic bridging group, connecting both phosphorus atoms, containing from 2 to 4 atoms in the bridge, which is substituted with at least one substituent or R represents a phenyl group, with both phosphorus groups bound to the 1,2-position.
Preferably the bridging group R represents a bivalent aliphatic bridging group, connecting both phosphorus atoms, containing from 2 to 4 atoms in the bridge, which is substituted with at least one substituent.
By “a bridge” is understood the shortest connection between both phosphorus atoms. Preferably, the bridging group R represents an alkylene group containing from 2 to 4 carbons atoms in the bridge, but it can also comprise a carbon chain, interrupted by a hetero atom, such as nitrogen, sulphur, silicon or oxygen atom. Preferably the bridge is a substituted alkylene group with at least one substituent and more preferably at least two substituents. Preferably the alkylene group is substituted with two to four substituents and more preferably with two to three substituents. Most preferably the alkylene group is substituted with two substituents. More preferably the bridging group R is a substituted dimethylene or trimethylene group, most preferably a substituted dimethylene group.
The substituents can be attached to any part of the bridge. In an advantageous embodiment, the carbon atoms of the bridge, which are connected to the phosphorus atoms, are substituted. In this case, the bidentate ligand has two chiral C-atoms and can have the R,R, SS, or R,S meso form. From a technical point of view, based on its greater activity, the R,S meso form is preferred. From a commercial point of view, a mixture of the possible stereochemical configurations of the bidentate ligand is preferred because this mixture is the most easy to prepare and such a mixture is inherently formed under the applied reaction conditions of the process of the invention. In another advantageous embodiment the substitution is vicinal.
The substituents can contain carbon atoms and/or hetero atoms, such as halides, sulphur, phosphor, oxygen and nitrogen. Preferably the substituents are hydrocarbyl groups. The hydrocarbyl groups itself can be aromatic, aliphatic or cycloaliphatic and can contain carbon atoms and hetero atoms. The hydrocarbyl groups include straight-chain or branched saturated or non-saturated carbon containing groups.
Preferred hydrocarbyl groups are alkyl groups, preferably having from 1 to 10 carbon atoms, more preferably from 1 to 4 carbon atoms. Linear, branched or cyclic alkyl groups can be used. Suitable alkyl groups include, methyl, ethyl, propyl, iso-propyl, butyl and iso-butyl. More suitably methyl groups are used.
Preferably, the bridge is substituted with at least two alkyl groups. Preferably the bridging group is substituted with two to four alkyl groups and more preferably with two to three alkyl groups. Most preferably the bridge is substituted with two alkyl groups.
Preferably the alkyl groups have from 1 to 10 carbon atoms, more preferably from 1 to 4 carbon atoms. Saturated or non-saturated, linear, branched or cyclic alkyl groups can be used. Suitable alkyl groups include, methyl, ethyl, propyl, iso-propyl, butyl, iso-butyl, tert-butyl and cyclopentyl. More preferably methyl groups are used.
Most preferably the bivalent aliphatic bridging group R is an alkylene group which is di-substituted in the bridge with two alkyl groups, most preferably with two methyl groups.
X
1
and X
2
represent a substituted or non-substituted cyclic group with at least 5 ring atoms, of which one is a phosphorus atom, and preferably with from 6 to 12 ring atoms. The cyclic group can be a monocyclic group, such as for example a phosphacyclohexyl or phosphacyclooctyl group, or a polycyclic group. Preferably the cyclic group(s) is/are a bicyclic group, such as for example a 7-phosphabicycloheptyl, a 8-phosphabicyclooctyl or a 9-phosphabicyclononyl group. Most advantageously both X
1
and X
2
represent a substituted or non-substituted 9-phosphabicyclononyl group. The 9-phosphabicyclononyl group can have several isomeric structures. For the purpose of the invention the [3,3,1
Drent Eit
Jager Willem Wabe
Sielcken Otto Erik
Toth Imre
DSW IP Assets B.V.
Killos Paul J.
Mayer, Brown, Rowe & Haw LLP
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