Transition Metal-Catalyzed Chemistry in Water at Room Temperature

University Of California Santa Barbara, Santa Barbara CA

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Abstract

DESCRIPTION (provided by applicant): A new paradigm for Pd-catalyzed cross-couplings between alkyl and aryl halides in water at room temperature will be further developed. Reactive, highly water-sensitive sp3-based organozinc reagents can be generated in situ and used as coupling partners, protected from their aqueous surroundings by a micellar environment. A study on the use of alkyl bromides as a less costly alternative to iodides will be undertaken. This new micellar nanotechnology will be applied to related cross-couplings of stereo-defined alkenyl halides. Such couplings would be an especially attractive alternative to Suzuki-Miyaura couplings that normally require prior formation of boronic acids or the equivalent. The stereochemistry of the products resulting from these couplings in water relative to that seen in organic solvents will also be compared. Related couplings applied to heteroaromatic halides will be studied, given the importance of heterocycles to the pharmaceutical industry. Novel transition metal-catalyzed tandem processes will be developed, both reactions of in this sequence to be conducted in water at room temperature. Stille couplings involving organostannane intermediates will also be investigated as coupling partners in micellar media. The first cases of couplings using nickel catalysis will also be further investigated in reactions of alkenyl halides with in situ-generated organozinc halides. A newly designed, inexpensive yet healthy surfactant has been identified and will be developed that enables room temperature couplings for several name reactions to be done in water. Higher levels of conversion relative to those seen in previous studies can be achieved, and hence, better yields of cross-coupling products are to be expected. The secret to this success is based on proper engineering of particle size, which better accommodates the intended chemistry.