Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2003-01-09
2004-11-09
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S102000, C502S103000, C502S104000, C502S109000, C502S159000, C502S232000, C502S400000, C502S402000, C502S406000, C502S407000, C502S514000, C422S091000, C204S290060, C546S002000
Reexamination Certificate
active
06815390
ABSTRACT:
This invention relates to a new catalyst system for fluorous biphasic catalysis processes which comprises functionalized plastic beads, monodisperse SiO
2
or SiO
2
flakes together with the catalyst in the fluorous phase. These functionalized particles are used as a support for catalysts in catalytic processes, especially in fluorous biphasic catalysis (FBC).
There is an increasing interest in the development of new liquid-liquid biphasic catalytic systems. One of the most interesting recent developments in homogeneous catalysis is the concept and application of fluorous biphase catalysis (FBC, I. T. Horváth and J. Rábai, Science, 1994, 266, 72). The principle of FBC is based on the limited miscibility of common organic solvents with perfluorinated compounds. A very attractive aspect of FBC is that it provides, by means of phase separation, an elegant solution of the catalyst/product separation problem associated with homogeneous catalysis. The FBC method shows appealing general features, such as the employment of nontoxic, reusable perfluorocarbons and the easy separation of the catalyst from reactants and products. Moreover, the inertness of perfluorocarbons and the high solubility of oxygen in these fluids would be particularly helpful in oxidation reactions.
Catalytic and stoichiometric reactions can be carried out in the fluorous biphase system, the simplest version being a two-phase mixture consisting of a perfluorcarbon (PFC) and a non-fluorinated solvent. The catalyst (or one of the reagents) is immobilized in the perfluorocarbon phase while the substrate (or substrates) and the product (or products) are dissolved in the organic solvent. Alternatively it is also possible to carry out the reaction under homogeneous conditions, by choosing a PFC/organic solvent couple that shows a thermally controlled miscibility.
In both cases when the reaction is finished the fluorous phase is easily recovered through simple phase separation, and can be reused without further treatment in a new reaction cycle.
The FBC technique is particularly adapted to reactions where the apolar substrates are converted to products of greater polarity, in that these are very easily expelled from the fluorous phase. Other positive aspects of the FBC technique are: the use of non-toxic PFC as a reaction medium, the lack of chemical coordination with catalysts, i.e. the possible improvement of the chemical stability of the homogeneous catalyst due to “site isolation”, and the easy separation of the catalyst and/or the exhausted reagents form the products. The future developments of the FBC approach are closely connected to the availability of efficient catalysts having, simultaneously, high solubility in the perfluorinated phase and electronic characteristics like those of analogous products soluble in normal organic solvents.
Successful application of FBC depends on rational design of catalysts that show high affinities to the fluorous phase, that are highly efficient and easy to prepare. Until now, there are some suitable catalysts known such as for example flurorous soluble metal catalysts that are based on molecular metal complexes containing conventional ligands modified with fluorinated groups (see Horváth, Acc. Chem. Res., 1998, 31, 641; or de Wolf et al., Chem. Soc. Rev., 1999, 28, 37). The best known such catalysts are perhaps rhodium trialkylphosphine complexes appended with fluorous ponytails such as [RhH(CO){P(CH
2
CH
2
C
6
F
13
)
3
}
3
]. The applicability of these complexes has been convincingly demonstrated by Horváth and Gladysz in the fluorous biphase hydroformylation (see Horváth et al., J. Am. Chem. Soc., 1998, 120, 3133), hydrogenation (see Rutherford et al., Catal. Today, 1998, 42, 381) and hydroboration (see Juliette et al., J. Am. Chem. Soc., 1999, 121, 2696).
Further Pozzi et al., prepared among others fluorous tetraarylporphyrin complexes with cobalt and manganese (see Chem. Commun., 1997, 69 and Tetrahedron, 1997, 52, 6145). Further examples of fluorous oxidation catalysts are Ru and Ni complexes of the fluorinated acetylacetonate anion {[(C
7
F
15
)C(O)CHC(O)(C
7
F
15
)]
−
} reported by Klement et al., Angew. Chem. Int. Ed. Engl., 1997 36, 1454.
A fluorous palladium complex [Pd{P(C
6
H
4
C
6
F
13
)
3
}
4
] turned out to be active in a cross-coupling of arylzinc bromides and aryl iodides (Betzemeier and Knochel, Angew. Int. Ed. Engl., 1997 36, 2623).
Bergbreiter and Franchina (Chem. Commun, 1997, 1531) described the synthesis of a fluorous phase soluble fluorocarbon polymer that covalently bind amine-containing reagents and that react with and separate from reagents in aqueous and hydrocarbon solvents.
Fluorous soluble polymer ligands have also been prepared and shown to be active and selective catalysts when combined with rhodium for the fluorous biphase hydroformylation of various olefins by Chen et al., Chem. Comm., 2000, 839.
However, the use of perfluorocarbons may have some disadvantages. Well known are the C
1
- and C
2
-fluorocarbons (freons) which are greenhouse gases and have become a major environmental problem because of their inertness. The higher perfluoroalkanes have lower vapor pressures and might therefore cause less environmental problems than their smaller chain analogues. About the impact, however, of longer perfluoroalkanes on the greenhouse effect, less is known. Therefore, it would be desirable and necessary to reduce the volume of the perfluorocarbons (PFC).
Furthermore, there is still a great need of suitable catalyst systems that are highly efficient, highly soluble in the fluorous phase, easy to prepare and easily recovered as the future developments of the FBC approach are closely connected to the availability of efficient catalysts having those advantages.
Surprisingly it has been found that functionalized plastic beads, monodisperse SiO
2
or SiO
2
flakes together with the catalyst in the fluorous phase are highly suitable as a new catalyst system for fluorous biphasic catalysis processes and for catalytic processes in general.
Thus, the subject of the present invention is a new catalyst system for fluorous biphasic catalysis processes comprising functionalized plastic beads, monodisperse SiO
2
or SiO
2
flakes associated with the catalyst in the fluorous phase.
Subject of this invention is also the use of plastic beads, monodisperse SiO
2
or SiO
2
flakes which are functionalized, as a support material for catalysts in catalytic processes.
The plastic beads, the monodisperse SiO
2
particles or the SiO
2
flakes are initially functionalized to facilitate interaction with the corresponding catalyst. This allows the chemistry to be performed in a thin film of liquid adhering to the surface of the beads or SiO
2
particles. As a result, a vastly reduced volume of the fluorinated solvent—which is expensive and not environmentally friendly—is required whilst continuing to facilitate a continuous process and to maintain the advantages of the FBC approach.
As mentioned before Bergbreiter and Franchina (Chem. Commun, 1997, 1531) and Chen et al., Chem. Comm., 2000, 839 described a similar approach using a fluorous soluble polymer catalyst or a fluorpolymer support for fluorous phase chemistry. In these cases the reagent is either covalently bonded (Bergbreiter) or already contains ligands which only require the introduction of a metal (Xiao). However, in the case of the support material of the present invention, the full catalyst (i.e. metal plus ligands) are added later. This allows variations to both the metal and ligands using one support material.
Furthermore, the polymeric beads of the present invention have no chemical bond between the support material and the catalyst.
Unlike the polymers of the prior art, the beads or the SiO
2
particles are not soluble in the fluorous layer—they associate with it due to the functionality on the surface. This decreases the incidence of emulsion formation when the hydrocarbons and fluorocarbons mix which is a disadvantage of the prior art approa
Hope Eric George
Pellatt Martin G.
Sherrington James
Vaughan Julian F. S.
Bell Mark L.
Brown Jennine M.
Merck Patent GmbH
Millen White Zelano & Branigan P.C.
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