N-Heterocyclic Carbenes towards Designing Molecular Catalysis

Sreejyothi, P. (2022) N-Heterocyclic Carbenes towards Designing Molecular Catalysis. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Sreejyothi P (16RS012)) 16RS012.pdf - Submitted Version Restricted to Repository staff only Download (8MB)

Abstract

The research works presented in this PhD thesis entitled “N-Heterocyclic Carbenes towards Designing Molecular Catalysis” discusses the utilization of NHCs, including classical (NHC) as well as non-classical carbenes (aNHC) as potential ligands for the synthesis of transition metal as well as main-group based complexes and their catalytic applications towards various organic transformations. In addition, the application of aNHC as a metal-free catalyst has also been explored. This thesis aims to show the utility of NHCs in three major sections, which include; A) Ligand for transition metal complexes B) Ligand for stabilizing reactive main group species C) As a metal-free catalyst This thesis is divided into three chapters, the first of which is “Introduction”, which discusses an overview of NHC. This section describes the history and development of NHCs over time and provides an overview of how NHC chemistry flourished in literature. The second chapter, “Results and Discussion”, is subdivided into four sections that provide a detailed description of the dissertation work carried out during the PhD tenure. Section 1 describes the utilization of palladium-based aNHC complex toward dehydrogenative cross-coupling of heteroarenes for yield C-C coupled products. Section 2 describes the use of higher nucleophilic aNHC as an efficient metal-free catalyst for Markovnikov ring-opening of epoxides to give secondary alcohols via hydroboration under ambient reaction conditions. This work represents the first metal-free report in this category. Section 3 discusses about the utilization of NHC-stabilized low-valent phosphorus molecules to activate chemically inert greenhouse gas, CO2, in the presence of silane to form formates. In addition, the NHC-phosphinidenes were efficient towards the activation of primary amides and subsequently resulted in the formylation of primary amides using CO2 under ambient reaction conditions. In the fourth section, NHC-stabilized phosphinidene was used as an efficient catalyst for the synthesis of γ- butyrolactones under ambient reaction conditions The third chapter consists of the “Experimental Section”, where all the experimental procedures for chapter 2 are described in detail. This section includes all the synthetic and characterization data for all the compounds discussed in this thesis. The characterization details, such as HRMS, NMR spectroscopic data, and single crystal X-ray measurement data for all new compounds, have been provided in this chapter.

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