Date of Degree
Palladium Catalysis, Cross-Coupling Reactions, Enantioenriched Nucleophiles, Stille Cross-Coupling, Tricyclohexyl Tin, Carbastannatrane
Organic chemistry exists in all aspects of everyday life from polymers to pharmaceutics. Formation of carbon-carbon bonds is essential for the synthesis of complex organic compounds. This goal can be achieved by using transition metal catalysts. Second-row transition metals such as Pd, Pt, Rh, and Ir have shown remarkable efficacy in these reactions. Metal-catalyzed cross-coupling reactions form carbon-carbon bonds between electrophiles and nucleophiles using transition metal catalysts. Pd is mainly used in this reaction.
Transition metal-catalyzed cross-coupling reactions that form a bond between two C(sp2) carbons have been widely studied over the past decades. C(sp2)-C(sp3) cross-coupling, however, faces many complications that can result in unwanted products, including the formation of isomers, racemates, and elimination products. The Stille reaction uses organotin compounds as nucleophiles in cross-coupling reactions. Our lab has designed reaction conditions to avoid unwanted β-hydride elimination pathways and enable unactivated alkyl tin compounds to undergo transmetallation and proceed through the catalytic pathway to give the desired cross-coupling product. Furthermore, we show that our system is highly stereospecific.
While cross-coupling reactions between a C(sp3) organotin compound and an aryl C(sp2) electrophile have been previously studied, vinyl systems have not been used as electrophiles. The third chapter of this report focuses on our attempt to study the cross-coupling between vinyl systems as electrophiles.
Another challenge in Stille reaction arises from the undesired transmetallation of spectator ligands from tin to palladium. Our lab showed when using tricyclohexyl groups as spectator ligands on tin if the 4th ligand is slightly more activated than a secondary alkyl group, we can selectively transmetallate the desired ligand unto tin. The 5th and 6th chapter of this report addresses the formation and reactivity of several of these alkyl tin compounds.
Ghaemimohammadi, Pejman, "Stereospecific Cross-Coupling Reactions of Vinyl Triflates and An Investigation of the Synthesis and Reactivity of Activated Alkyltricyclohexylstannanes" (2024). CUNY Academic Works.