Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phosphorus-containing reactant
Reexamination Certificate
2001-12-11
2003-11-11
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phosphorus-containing reactant
C528S051000, C528S052000, C528S056000, C528S485000, C528S492000
Reexamination Certificate
active
06646106
ABSTRACT:
The invention relates to an optically active diphosphorated polymeric ligand of use in the preparation of metal complexes intended for asymmetric catalysis.
Asymmetric catalysis has experienced considerable growth in recent years. It exhibits the advantage of resulting directly in the preparation of optically pure isomers by asymmetric induction, without it being necessary to carry out resolution of racemic mixtures.
2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) is an example of a diphosphorated ligand commonly used in the preparation of metal complexes for the asymmetric catalysis of hydrogenation, carbonylation or hydrosilylation reactions, reactions for the formation of C—C bonds (such as allylic substitutions or Grignard cross-couplings) or even reactions for the asymmetric isomerization of allylamines.
The metal complexes prepared from BINAP are complexes of rhodium, iridium, palladium, platinum or ruthenium, which are very expensive metals.
Because of the high cost of the metals constituting them, industrial processes using these metal complexes as catalyst necessarily comprise stages devoted to their recovery and to their recycling.
In point of fact, metal complexes of the type of those prepared from BINAP are generally employed in homogeneous catalysis, that is to say that they are used in solution in the reaction medium.
Under these circumstances, the stages of extraction of the catalyst and of recovery are complex and render the implementation of these processes on an industrial scale problematic and laborious.
The invention is targeted at solving this problem by providing in particular a more economical process in which the stages of extraction of the catalyst, of recovery and of recycling are simplified and are compatible with implementation of the process on an industrial scale. According to this process, the metal catalyst is solid and is separated from the reaction medium by simple filtration, the catalysis taking place in the heterogeneous phase.
The novelty of the invention is based on the specific nature of the metal complex used as catalyst and more specifically on the nature of the phosphorated ligand used to prepare the catalyzing metal complex, which nature determines the feature of low solubility of the catalyst.
The development of phosphorated metal complexes which can be used in heterogeneous catalysis and which can be separated from the reaction medium by filtration has already been envisaged in the art.
D. J. Bayston et al. have described, in J. Org. Chem., 1998, 63, 3137-3140, a catalyst prepared from a polymer ligand composed of a chiral diphosphine grafted to a polymer support. The formula of this ligand can be represented diagrammatically as follows, where PS denotes a polymer support composed of polystyrene and Ph denotes the phenyl radical:
More generally WO 98/12202 discloses polymer ligands for the preparation of metal complexes intended for asymmetric catalysis. These ligands, of formula:
in which R
1
is —Y
0
—X
0
—R
4
where R
4
comprises an insoluble support derived from a polystyrene, from a polyamide or from a polymer resin, are also composed of a chiral diphosphine grafted to a polymer support.
The catalyzing complexes prepared from the ligands of the prior art only exhibit a single chiral site per polymer chain, which requires the involvement of large catalytic masses for effective catalysis, the mass of the polymer chain adding to the mass of the grafted chiral molecule.
Furthermore, the ligands of the prior art do not exhibit the C
2
axial symmetry of the BINAP molecule. In point of fact, it is known that polymeric ligands with C
2
axial symmetry result in excellent enantiomeric selectivities in the catalysis of asymmetric reactions.
The polymer of the invention which can be used as ligand in the preparation of catalyst complexes exhibits several optically active centers and a variable structure, which allows in particular the preparation of polymers exhibiting, as a whole, C
2
axial symmetry.
The polymer of the invention is composed of a linkage of two types of units.
The first type of unit is the residue of a chiral diphosphine exhibit a C
2
axis of symmetry, with the exclusion of any other element of symmetry, and carrying two identical polymerizable functional groups.
The second type of unit is the residue of a monomer which can polymerize with said functional groups, that is to say a monomer comprising two identical functional groups capable of reacting with the functional groups of the chiral diphosphine.
Due to the recurrence of the chiral unit in the polymer chain, much lower amounts of the corresponding metal catalyst are necessary for effective catalysis of the asymmetric reactions. Furthermore, starting from a polymerizable monomer also exhibiting a C
2
axis of symmetry, a polymer is obtained exhibiting, as a whole, C
2
axial symmetry, which leads to much better enantio-selectivity in comparison with the grafted polymers of the prior art.
More specifically, the invention relates to an optically active polymer which can be used as ligand in the preparation of metal complexes intended for asymmetric catalysis. These polymers can be obtained by polymerization of a chiral diphosphine exhibiting a C
2
axis of symmetry, with the exclusion of any other element of symmetry, with one or more polymerizable monomers. According to the invention, the chiral diphosphine is composed of a chiral body (or chiral backbone) carrying two identical functional groups capable of reacting with the polymerizable monomers.
The notion of C
2
axis of symmetry and plane of symmetry is described by Kurt Mislow in “Introduction to stereochemistry”, W. A. Benjamin Inc. New York, Amsterdam, 1965.
A molecule exhibiting a C
2
axis of symmetry is such that, by rotation of this molecule by 180° about the axis of symmetry, a molecule is obtained which is exactly superimposable on it.
The chiral diphosphines which can be used in the preparation of the polymers of the invention include molecules with a chirality which results from the spatial arrangement of the atoms constituting them (these molecules are described as atropisomers), molecules with a chirality carried by the phosphorus atoms and molecules with a chirality carried by carbon atoms.
The diphosphines of atropisomer type do not comprise an asymmetric carbon. In these molecules, rotation about single bonds is prevented or greatly slowed down.
Atropisomeric diphosphines which are particularly preferred are those having a chiral body (or backbone) corresponding to the following formula:
in which:
Ar
1
and Ar
2
are independently a saturated, unsaturated or aromatic carbocycle;
R
1
and R
2
are independently a hydrogen atom; a Z group; or an —XZ group where X is O, S or —NT; and
Z and T are selected independently from a saturated aliphatic hydrocarbonaceous group optionally interrupted by O, S and/or N; a saturated, unsaturated or aromatic carbocyclic group; or a saturated aliphatic hydrocarbonaceous group substituted by one or more saturated, unsaturated or aromatic carbocyclic groups, in which the aliphatic group is optionally interrupted by O, S and/or N; it being understood that T can additionally be a hydrogen atom; or else two R
1
and R
2
groups, attached to the same phenyl nucleus, together form an unsaturated or aromatic carbocycle or alternatively together form an unsaturated or aromatic heterocycle.
In the context of the invention, the term “carbocyclic radical” is understood to mean an optionally substituted monocyclic or polycyclic, preferably C
3
-C
50
, radical. It is advantageously a C
3
-C
18
radical, preferably a mono-, bi- or tricyclic radical.
When the carbocyclic radical comprises more than one ring (case of polycyclic carbocycles), the rings can be condensed two by two or attached two by two via &sgr; bonds. Two condensed nuclei can be orthocondensed or pericondensed.
The carbocyclic radical can comprise a saturated part and/or an aromatic part and/or an unsaturated part.
Cycloalkyl groups are examples of saturated carbocyclic radicals.
The cycloa
Colasson Benoît
Halle Rob Ter
Lamouille Thierry
Lemaire Marc
Saluzzo Christine
Burns Doane Swecker & Mathis L.L.P.
Rhodia Chimie
Truong Duc
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