Regioselective and Stereospecific Rhodium-Catalyzed Allylic Substitution Reactions With Nitrile-Stabilized Anions: Construction Of Acyclic Remote Stereocenters and Chemoselective Hydrogenation of Nitroarenes to Anilines using Heterogeneous Nickel Foams

Abstract

The thesis is divided into three chapters, featuring a comprehensive literature review, followed by two research chapters that are split into two different areas of research in homogeneous rhodium and heterogeneous nickel catalysis. Chapter 1 commences with a brief introduction on nitrile-stabilized anions and historical developments on the transition metal-catalyzed allylic alkylation reaction, which is followed by a detailed account on nitrile-stabilized anions in asymmetric transition metal-catalyzed allylic alkylation reactions. The review is divided into three major subsections focused on the type of selectivity, namely, diastereoselective, enantiospecific and enantioselective transformations featuring nitrile-stabilized anions and delineates the achievements in each area. Chapter 2 features the development of silyl-stabilized nitrile anions in the regioselective and stereospecific rhodium-catalyzed allylic alkylation reaction for the construction of remote stereocenters. The chapter opens with the discovery and development of the rhodium-catalyzed allylic substitution reaction and follows by highlighting the utility of organosilicon compounds with particular focus on their utility as nucleophiles in transition metal-catalyzed allylic substiution reactions. The following two sections will discuss our work on the regioselective and stereospecific rhodium catalyzed allylic cyanomethylation using a silyl-stabilized acetonitrile equivalent for the construction of acyclic β-quaternary and ternary stereogenic nitriles. Finally, our initial progress towards the development of a regioselective and stereospecific rhodium-catalyzed allylic substitution reaction with γ-silyl allylic α-amino nitrile as homoenolate equivalents for the construction of acyclic γ-functionalized carboxylic acids shall be discussed. Chapter 3 highlights our efforts towards the chemoselective hydrogenation of substituted nitroarenes to anilines using heterogeneous open-pore nickel foams. After a brief introduction on the hydrogenation of nitroarenes to anilines using heterogeneous catalysis, our development of a highly chemoselective nickel foam variant of this process is discussed. We showcase the utility of the transformation for the synthesis of highly substituted anilines using mild conditions. Additionally, the structural integrity and morphology of the nickel foams are analyzed using scanning electron microscopy (SEM), which give insight into the unique etching pattern of the heterogeneous nickel catalyst.