Nonpolar phase-soluble methathesis catalysts

Abstract

One embodiment of the invention provides polyisobutylene (PIB) oligomers that are end-functionalized with ruthenium (Ru) catalysts. Such nonpolar catalysts can be dissolved in nonpolar solvents such as heptane, or any other nonpolar solvent that is otherwise not latently biphasic (i.e., if two or more solvent components are present, they remain miscible with each other throughout the entire reaction process, from the addition of substrate through to the removal of product). Substrate that is dissolved in the nonpolar solvent with the catalyst is converted into product. The lower solubility of the product in the nonpolar solvent renders it easily removable, either by extraction with a more polar solvent or by applying physical means in cases where the product precipitates from the nonpolar solvent. In this manner the catalysts are recycled; since the catalysts remain in the nonpolar solvent, a new reaction can be initiated simply by dissolving fresh substrate into the nonpolar solvent.

Description

[0001]This application claims the benefit of priority to U.S. Provisional Application No. 60 / 997,093, filed Oct. 1, 2007, which is herein incorporated by reference in its entirety.FIELD OF THE INVENTION[0002]The invention relates to methods and compositions useful for catalyzing chemical reactions. In particular, the invention is drawn to reactions that afford efficient catalyst recycling and reusability. Even more particularly, the compositions and methods provided by the invention relate to the provision of a single nonpolar reaction solvent that is not latently biphasic and a catalyst that is soluble therein.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 reacti...

AI Technical Summary

Benefits of technology

[0011]One embodiment of the present invention is directed to a reaction composition that comprises a nonpolar solvent that is not latently biphasic, a catalyst that is complexed to a nonpolar support (i.e., catalyst-support complex), and a molecule that is a substrate for the catalyst. With this embodiment, the catalyst-support complex and substrate molecule are both dissolved in the nonpolar solvent; however, the product of the reaction is less soluble in the solvent compared to the molecule. In other embodiments of the composition, the product is completely insoluble in the solvent. The partial or complete insolubility of the product in the reaction solvent, coupled with the complete solvency of the catalyst-support complex, allows for the facile separation of the product from the catalyst; the latter component can thus be recycled for another round of substrate-to-product conversion.

[0013]The nonpolar support of the inventive composition can comprise, for example, polyisobutylene, polyethylene, poly(N-octadecylacrylamide), polysiloxane, polyamidoamine, poly(1-alkene), or polypropylene. An N-heterocyclic carbene moiety or benzylidene moiety, for example, can be used to bridge the catalyst to the support. Components that are chosen to attach to the support and act as a ligand for the catalyst should not impede the ability of the resulting catalyst-support complex to dissolve in a nonpolar solvent.

[0016]In a particularly preferred embodiment of the instant invention, the reaction composition comprises heptane as the solvent, a ruthenium catalyst that is in complex with a polyisobutylene-containing support, and a heptane-soluble substrate molecule. In this embodiment, the catalyst-support complex is heptane-soluble, and the substrate molecule is a substrate for ruthenium. The product of the reaction occurring between the ruthenium catalyst and substrate has little or no solubility in heptane. This feature permits facile separation of the product from the catalyst, the latter of which can then be used in a reaction with newly added substrate. Certain aspects of this embodiment may also incorporate an N-heterocyclic carbene moiety as a bridge between the polyisobutylene support and the ruthenium complex.

[0017]The instant invention is also drawn to a method of catalyzing a chemical reaction having the steps of providing a reaction composition as described above, allowing the substrate molecule to be catalyzed into product, and separating the product from the reaction composition. The product separation step can be performed in different ways. One strategy for separation is through the use of physical means, such as siphoning, filtering, or decanting, all of which can be employed if the product is nearly or totally insoluble in the solvent. Another strategy for separation is through extraction of the product by adding and removing a second solvent to the reaction composition; the second solvent can be a polar organic solvent such as acetonitrile, for example. In this latter aspect of the inventive method, the product is preferably soluble in the second solvent compared to the nonpolar solvent of the reaction composition. Throughout either process (physical separation or extraction), the catalyst-support complex remains dissolved in the nonpolar solvent. This feature allows for the step of reusing the catalyst-support complex by dissolving fresh substrate into the nonpolar solvent.

Problems solved by technology

With this embodiment, the catalyst-support complex and substrate molecule are both dissolved in the nonpolar solvent; however, the product of the reaction is less soluble in the solvent compared to the molecule.

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