Abstract

The development of new catalysts for organic synthesis is an important pursuit that enables the discovery of new and more efficient reactions and the identification of new reaction mechanisms. Cooperative catalytic systems and bimetallic catalysts represent unique approaches to catalyst development that achieve reactivity that cannot be obtained with a single catalyst or metal. These types of catalysts can activate substrates in unique ways, facilitate reactions under mild conditions, increase substrate scope, and provide access to completely new transformations. The first part of this work describes the development of a cooperative nickel-titanium-catalyzed amination of allylic alcohols. The cooperative effects of the two metals allow for mild reaction conditions that tolerate a larger substrate scope. A unique tandem cyclization amination is also shown that only takes place using both metals. Additionally, the benefits of using boron tethers are shown in the boron templated dimerization of allylic alcohols. This dimerization forms boron-protected 1,3-diols. Derivatization studies were performed that show the synthetic utility of this new transformation. The second portion of this work focuses on the development of a novel bimetallic rhodium complex and its use in organic synthesis. Using a 2-phosphinoimidazole ligand in the presence of carbon monoxide, a bimetallic Rh(II) complex is formed and purified in high yield. This complex shows versatile reactivity and performs reactions that are traditionally catalyzed by both Rh(I) and Rh(II) complexes. An X-ray crystal structure and DFT calculations confirm the bimetallic nature of this catalyst. Our catalyst shows a unique ability to perform reductive eliminations with weak nucleophiles where other rhodium catalysts perform ï¢-hydrogen elimination. The utility of this catalyst is shown in the intramolecular hydroamination of allenes to form small and medium sized nitrogen heterocycles. We also describe the development of a bimetallic trifluoroacetoxylation of allenes. This reaction only occurs with our bimetallic catalyst and over 30 examples are shown.

Degree

PhD

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

Rights

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