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  Phase selective polymer supports for catalysisUSPTO Application #: 20070203019Title: Phase selective polymer supports for catalysis Abstract: Phase-selective soluble polymer supports for catalysts are described. The catalysts utilize polystyrene copolymers having enhanced solubility in nonpolar solvents. Other catalysts of the invention utilize polyisobutylene supports. Methods of catalyzing chemical reactions using latent biphasic solvents are also disclosed. (end of abstract) Agent: Howrey LLP - Falls Church, VA, US Inventors: David E. Bergbreiter, Chunmei Li, Jacqueline O. Besinaiz, Jun Li, Shayna D. Sung USPTO Applicaton #: 20070203019 - Class: 502150000 (USPTO) Related Patent Categories: Catalyst, Solid Sorbent, Or Support Therefor: Product Or Process Of Making, Catalyst Or Precursor Therefor, Organic Compound Containing The Patent Description & Claims data below is from USPTO Patent Application 20070203019. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application is a non-provisional of U.S. Provisional Patent Application Ser. No. 60/408,586, filed Sept. 6, 2003, which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The invention relates to methods and compositions useful for catalyzing chemical reactions. In particular, phase selective polymer supports for catalysts and methods of using these supports to facilitate the recovery of catalysts are disclosed. BACKGROUND OF THE INVENTION [0003] Polymer supported catalysts are widely used in chemical processes. Much of the technology that is presently available derives from the solid-phase peptide synthesis techniques developed by Merrifield. These techniques are based on insoluble cross-linked polystyrene supports. Catalysts supported on Merrifield resins can be recovered from reaction media using a solid/liquid separation technique such as filtration. [0004] With the growing interest in environmentally friendly, or "green" chemical processes, there is an emphasis on the ability to reuse materials and to minimize amounts of solvents required for a given process. Filtration is typically a relative solvent-intensive process, because the recovered solid is typically rinsed with additional solvent. Further, some polymer supported catalysts suffer from decreased activity once they are isolated via filtration. This impacts their potential to be reused multiple times. [0005] Soluble polymer supported catalysts have been developed. These catalysts can be recovered from the reaction medium either by precipitation followed by filtration, by liquid/liquid separation, or by ultrafiltration using a filtration membrane. Precipitation/filtration obviously suffers from the same drawbacks associated with the filtration of insoluble polymer supported catalysts, described above. Inadequate partitioning of the catalyst into the desired liquid phase often impairs liquid/liquid separations. For example, liquid/liquid separation is impractical if the catalyst and the product are both soluble in the same phase. Ultrafiltration of soluble catalysts using membranes has enjoyed some success, but the recycled catalysts often suffer from some loss of activity. [0006] An alternative way of using a soluble catalyst is to use a biphasic system wherein the catalyst is preferentially soluble in one phase and the substrate and/or products are soluble in the other phase. During reaction, the biphasic solvent system is vigorously mixed to ensure maximum contact between the catalyst and substrate. After reaction, the mixture is allowed to settle and the product phase is removed, leaving the catalyst phase available for recycling. The drawback to biphasic systems is that the presence of multiple phases introduces kinetic barriers to reaction. [0007] The drawbacks associated with biphasic solvent systems can be overcome by using a solvent system that is monophasic under one set of conditions and biphasic under a different set of conditions. For example, liquid-liquid biphasic systems that exhibit an increase in phase miscibility at elevated temperature together with soluble polymer-bound catalysts that have a strong phase preference at ambient temperature are described in "Palladium-Catalyzed C--C Coupling under Thermomorphic Conditions," by Bergbreiter, et al., J. Am. Chem. Soc., 2000, 122, 9058-64 and in "Nonpolar Polymers for Metal Sequestration and Ligand and Catalyst Recovery in Thermomorphic Systems," by Bergbreiter, et al., J. Am. Chem. Soc., 2001, 123, 11105-06. [0008] There is a need in the art for catalytic methods that allow for the efficient separation of the catalyst from the reaction product and the recycling of the catalyst. It is desirable that such methods operate with minimal additional solvent to effect the separation of the catalyst. SUMMARY OF THE INVENTION [0009] Accordingly, one aspect of the present invention is a method of catalyzing a reaction using a solvent system that is monophasic under one set of conditions and biphasic under a different set of conditions. The chemical reaction will occur when the solvent system is monophasic. At the end of the reaction, the solvent system is switched to the biphasic state. The reaction product is preferentially soluble in one of the phases and the polymer-supported catalyst is preferentially soluble in the other phase. [0010] According to one embodiment, the product-containing phase can be removed and replaced by a fresh polar phase and more reactants, allowing the catalyst to be recycled. [0011] A further aspect of the present invention is a catalytically active composition comprising a polystyrene copolymer, the polystyrene copolymer comprising styrene monomers substituted with one or more catalytically active functional groups and pendant styrene groups substituted with one or more functional groups that increase the solubility of the polystyrene copolymer in a non-polar solvent. [0012] A still further aspect of the present invention is a catalytically active composition comprising a catalytically active functional group bound to polyisobutylene. DETAILED DESCRIPTION OF THE INVENTION [0013] One aspect of the present invention is a method of catalyzing a chemical reaction using a latent biphasic liquid solvent system. As used herein, the term latent biphasic system refers to a mixture of solvents, wherein the mixture is monophasic under one set of conditions and biphasic under a different set of conditions. The liquid solvent components are miscible in the monophasic state. The biphasic state comprises a more polar phase and a less polar phase, with the two phases being layered, one on top of the other. The latent biphasic system facilitates separating the catalyst from the reaction products because the system is designed so that the catalyst is preferentially soluble in one phase of the biphasic mixture and the products are preferentially soluble in the other phase. Typically, the chemical reaction will occur when the solvent system is in the monophasic state. Because the reaction medium is in the monophasic state, the reaction is not impeded by phase transfer phenomena or other kinetic barriers associated with multiple phase reactions. Following the reaction, the solvent mixture is switched to the biphasic state to facilitate separating the products from the catalyst. [0014] According to one embodiment of the invention, the phase containing the catalyst is recycled and used for multiple reaction cycles. For example, if the catalyst is preferentially soluble in the less polar of the phases of the biphasic mixture and the reaction products are preferentially soluble in the more polar of the phases, then a recycling reaction protocol is defined by the following sequence: [0015] 1) A substrate and/or reactants are present in the latent biphasic system, along with the catalyst. The reaction proceeds while the latent biphasic system is in the monophasic state. [0016] 2) The latent biphasic system is perturbed to switch the system to the biphasic state comprising a more polar phase containing the reaction products and a less polar phase containing the catalyst. [0017] 3) The more polar phase containing the reaction products is separated from the less polar phase containing the catalyst. [0018] 4) Additional substrate and/or reactants, along with the more polar solvent components are added to the catalyst-containing phase. The solvent system is switched to the monophasic state and the reaction proceeds. The cycle is repeated. [0019] Mixtures of solvents have a spectrum of phase behavior. For example, ethanol and water are miscible in all proportions, as are ethanol and heptane. However, mixtures containing all three of these components vary in miscibility depending on several factors, including the proportions of each of the components, temperature, and the presence or absence of solute. For example, a 10.0:9.5:0.5 (vol:vol:vol) mixture of heptane, ethanol, and water is monophasic at 25.degree. C., but a mixture of the same components with a ratio of 10.0:9.5:1.0 is biphasic at the same temperature. Therefore, heptane, ethanol, and water can be used as components for a latent biphasic system. The monophasic state is a mixture having the composition of about 10.0:9.5:0.5 (vol:vol:vol). Adding an additional 0.5 volumetric equivalents of water perturbs the system and induces phase separation. [0020] Countless latent biphasic systems are possible. For example, a miscible mixture of 10 mL each of toluene and 95% ethanol/water becomes biphasic on addition of 0.5 mL of water. Likewise, a mixture of tert-butylmethylether, ethanol, and water having a volumetric ratio of 10.0:6.0:4.0 is miscible. Adding an additional 2.5 volumetric equivalents of water switches the mixture to a biphasic state. It is within the ability of one of skill in the art to derive other latent biphasic solvent systems without undue experimentation. [0021] Phase separations in many latent biphasic solvents can be initiated by adding a salt to the solvent. If a salt is a side product of the catalytic reaction of interest, then the production of the salt in situ can induce phase separation. [0022] Other examples of latent biphasic systems include mixtures of solvents that are homogeneous within one temperature range and biphasic within a different temperature range. Herein, these systems are referred to as thermomorphic latent biphasic systems. For example, a mixture of equal volumes of heptane and 90% ethanol/water are completely miscible at 70.degree. C. Cooling the mixture to 25.degree. C. produces a biphasic mixture with a less dense non-polar phase containing mostly heptane and a denser polar phase of mostly ethanol and water. Likewise, N,N-dimethylacetamide and heptane are immiscible at 25.degree. C. but are miscible in all proportions above 65.degree. C. [0023] In a separation scheme utilizing latent biphasic mixtures for catalytic reactions, it is desirable that the catalyst selectively partition into one of the two phases of the biphasic state. For example, if the catalyst is preferentially soluble in the non-polar phase, the ratio of the amount of catalyst that ends up in the non-polar phase compared to the amount that ends up in the polar phase is ideally greater than 10:1, more ideally greater than 100:1 and even more ideally greater than 200:1. If the catalyst-containing phase is to be recycled through multiple reaction cycles, it is desirable that the ratio be at least about 200:1. Continue reading... Full patent description for Phase selective polymer supports for catalysis Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Phase selective polymer supports for catalysis patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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