Abstract
The thesis discusses a few transition metal-catalyzed reactions and their application in organic systhesis. For convenience and better understanding, the thesis is divided into four chapters. The first and the last two chapters deals with ruthenium-catalyzed reactions and application in organic synthesis. The synthesis of heterocyclic systems from acyclic or cyclic building blocks is typically achieved through the use of the heteroannulation or intramolecular cyclization process from organometallic complexes. The first chapter describes an efficient regioselective cyclization of 2-alkynyl-phenol-alkanol derivatives via 6-endo-dig mode catalyzed by Tp[Ru]PF6 catalyst. The synthetic utility of this cyclization is manifested in the synthesis of heterocylcles such as isochromene derivatives. These reactions are important and challenging topic in organic synthesis. The second chapter establishes a facile, effective route for synthesizing 2,5-disubstituted furans via [RhCl(CO2)]2-catalyzed cyclization of epoxyalkanes. These useful method could be applied to the synthesis of complex natural products. Furan molecules are essential part of some important natural products and pharmaceuticals. The third chapter describes the synthesis of 1,2-diketones via an efficient rearrangement of a,b-epoxyketones using a new catalytic system, Tp[Ru]PF6. These 1,2-diketone are key intermediates in the synthesis of a wide range of natural products. 1,2-Diketones and organic moieties could be subjected to a wide variety of further chemical transformations to give potential intermediates, as precursors for the synthesis of natural products as well biologically active compounds. The last chapter describes a new methodology involving Zn(OTf)2 as catalyst providing an easy and effective approach for synthesizing indoles, benzofurans, and oxazoles through the cyclization of propargyl alcohols with commercially available starting materials. For the synthesis oxazoles, we have used co-catalyst Tp[Ru]PF6 along with Zn(OTf)2. The mechanism of this process was completely elucidated. These significant methods are applicable to the heterocylces synthesis. Indoles, benzofurans, and oxazoles moieties represents an important substructures in many natural products, and development of novel synthetic approaches to these skeletons continues to be an important goal.