Abstract
In recent years, transition metal-catalyzed C–H bond activation and annulation reactions were emerged as an important strategy in the synthesis of natural product, bioactivity molecules and material compounds. In this context, our group also focus on the hot research field of C–H bond activation reaction. The thesis concentrated on the synthesis of polycyclic pyridinium, quinolizinium, and pyridinium salts by rhodium- and ruthenium- catalyzed C–H bond activation and annulation reactions. In addition, copper promoted quinoline synthesis from benzylazides and alkynes through arylmethyl azides rearrangement is demonstrated in the final chapter. Chapter 1 describes an efficient and convenient method for the synthesis of highly substituted polycyclic pyridinium salts from various 2-arylpyridines and alkynes via a Rh(III)-catalyzed C–H bond activation and annulation reactions under an atmosphere of O2. The proposed mechanism is supported by the isolation of a five membered rodacycle. Primary photophysical studies were also performed on the new pyridinium salts compound in OLED materials. Chapter 2 introduces effectual methods to the synthesis of quinolizinium salts from 2-vinylpyridines and alkynes via Rh(III) or Ru(II)-catalyzed C–H activation and annulation reactions. The present quinolizinium salts can be readily converted to the corresponding tetrahydroquinolizinium compounds by hydrogenation. Chapter 3 elaborates a synthetic method for highly substituted pyridinium salts from the multicomponent reaction of vinyl ketones, amines, and alkynes using a rhodium catalyst. The catalytic reaction proceeds via an in situ generated imine-assisted Rh(III)-catalyzed vinylic C–H activation reaction. Synthesis of highly substituted pyridines from pyridinium salts also was demonstrated. Chapter 4 illustrates a new route for quinolizinium salts synthesis from 2-ethylpyridines and alkynes using cooperative catalysis by copper and rhodium with high yields, broad substrate scope and functional group tolerance. Detailed mechanistic studies suggest that the 2-vinylpryridine is formed in situ from 2-ethylpyridine by a copper promoted C(sp3) –H hydroxylation followed by dehydration. Later, a Rh(III)-catalyzed pyridine directed vinylic C(sp2) –H activation and [4+2] annulation with alkynes provide the final product. Chapter 5 shows a technique toward the synthesis of quinolines via copper promote azide rearrangement and intermolecular cycloaddition reaction with internal alkynes. In addition, the method was applied to the synthesis of biological active quinoline compounds.