Studies on the Synthesis of Modified Carbazole Scaffolds via Pd(II)-Catalyzed C-H Functionalization

Abstract

Carbazole scaffolds are an important nitrogen-containing heterocyclic compound, known to possess an extensive range of application in various fields of chemical sciences. Several carbazole embedded naturally occurring alkaloids have profound biological activities such as anticancer, anti-Alzheimer, anti-HIV etc. Various FDA approved drug molecules such as alectinib, carvedilol, carazolol etc constituting the carbazole moiety are well utilized for their treatment in hypertensive disorders, metastatic breast cancer and small cell lung cancer. Apart from being a bio-active molecule, it is well recognized as a vital component in material sciences displaying a significant role in organic light-emitting diodes, photovoltaics and solar cells. Owing to widespread applications, there exists several methods for the synthesizing carbazole motifs via classical routes, transition metal catalysed C-C and C-N oxidative coupling. In particular, cross-coupling reactions are well utilized for the synthesis as well functionalization of carbazole scaffolds. Although these reactions have led to essential discoveries, but these are often associated with certain limitations. In contrast, transition-metal catalysed C-H activation/functionalization has surfaced as an alternative to various traditional approaches developed in the past. This protocol generally involves the functionalization of organic molecules by activating the unreactive carbon hydrogen bonds via transition metal catalyst, thereby making the synthesis more site-selective and step-economical. Keeping in mind the significance of this approach and varied applications of carbazole scaffold, this thesis aims to synthesize carbazole-based unnatural amino acids, functionalized carbazole motifs, biaryl-based carbazoles, unsymmetrical bis carbazoles and π-extended bis carbazoles using palladium-catalyzed bidentate directing group-assisted C-H functionalization approach.