Abstract
ABSTRACT Transition-metal-catalyzed direct conversions of unreactive, less polar CH bonds into numerous organic functional groups by uniting commercially available π-components, which brought a revolution recently in synthetic methodologies for the production of pharmaceuticals, natural products and for opening new routes to organic reactions. Because it can introduce simple conversions, consumes low catalyst loading, inexpensive, readily available starting materials and environmentally friendly conditions. A large variety of metal catalysts, especially rhodium, palladium and ruthenium catalysts are now useful for the efficient catalytic conversion of CH bonds. The uses of rhodium and ruthenium complexes for CH activation via insertion of unsaturated substrates to generate new CC bonds are considerable interest in organic synthesis. In this regard, this thesis describes seven new reactions that focus on the various directing groups with various alkynes and alkenes by rhodium and ruthenium catalyzed CH activations. The CH functionalization reaction affords various functionalized heterocyclic compounds and yields out new five membered and six membered rings. On the other hand carbocyclization, annulation, and insertion reactions of ketone, aldehyde, azo, hydrazine hydrochloride and pyridine containing arenes with simple alkynes and alkenes afforded biologically active indenols, isocoumarins, cinnolinium salts, indoles and amide derivatives in one-pot manner. For better perceptive, I divided this thesis into six chapters. The first four chapters describe about rhodium(III)-catalyzed CH bond activation of aryl ketones, aryl aldehydes, azobenzenes, and aryl hydrazine hydrochlorides with internal alkynes. The fifth chapter describes about rhodium(III)-catalyzed ortho alkenation and cyclization of azobenzenes with alkenes. The final chapter deals with ruthenium-catalyzed amidation of 2-arylpyrindes with isocyanates by CH activation. Chapter 1 describes a regioselective synthesis of indenols by rhodium-catalyzed CH activation and carbocyclization of aryl ketones and alkynes. The catalytic system proceeds via CH activation followed by regioselective insertion of alkynes to give biologically useful, substituted indenols in excellent yields. Chapter 2 deals about a synthesis of highly substituted isocoumarin derivatives from aryl aldehydes and alkynes via C−H activation as a result of rhodium catalyst. This methodology shows in-situ oxidation of aldehydes affords acid and ortho CH activation. This simple method offers an alternative and less expensive way to the synthesis of isocoumarins. Chapter 3 illustrates the rhodium (III)-catalyzed synthesis of cinnolinium salts starting with azobenzenes and alkynes: application to the synthesis of indoles and cinnolines. The reaction path way appears to be the first example employing rhodium catalyzed CH activation and annulation to the synthesis of cinnolinium salts. In addition, the cinnolinium salt products have been successfully applied to the synthesis of three important classes of bioactive compounds and advanced materials namely indole, indoloindole and cinnoline derivatives. Chapter 4 elaborates an efficient regioselective synthesis of indoles from aryl hydrazine hydrochlorides and alkynes via CH activation. This reaction proceeds through the hydrazone group directed selective ortho CH bond activation and insertion of NN bond gave indoles in highly regioselective manner. Chapter 5 reveals a new insertion and aromatization of azobenzenes with alkenes via RhCp*-catalyzed CH activation. The present rhodium catalyzed CH activation reaction is successfully applied to various acrylates and acrylamides to synthesize aminoindole-2-carboxylates and 2-carboxyindoles. Chapter 6 shows a Ru(II)-catalyzed amidation of 2-arylpyridines with isocyanates via CH activation. This method provides an opportunity for the synthesis of various amidated 2-arylpyridines using less expensive ruthenium catalyst under mild reaction condition.