ASYMMETRIC SYNTHESIS MEDIATED BY NOVEL ORGANOCATALYSTS AND REACTIONS OF 2-ALKENYL-p-BENZOQUINONES

Abstract

The thesis entitled "Asymmetric Synthesis Mediated by Novel Organocatalysts and Reactions of 2-Alkenyl-p-benzoquinones" is divided into five chapters. Novel Camphor-based prolinamides have been synthesized and employed as efficient chiral organocatalysts for the C-C bond forming reactions such as aldol and Michael addition reactions. Furthermore, stereoselective domino reactions of alkenyl-l,4-benzoquinones with enol ethers have been carried out to furnish novel angular fused heterocyclic quinoid ring systems. CHAPTER-1: Introduction Enantioselective synthesis has become most important area in synthetic organic chemistry, medicinal chemistry, agricultural chemistry, natural products chemistry and pharmaceutical industries. New catalytic asymmetric reactions give us the opportunities to develop more efficient methods for the synthesis of various highly potent chiral compounds, with successful applications for the synthesis of various complex natural products as well as industrial production. However, in catalytic approach, catalytic amount of small organic molecules or chiral metal complexes is employed in the reaction and its regeneration and participation in parallel catalytic cycle complete the reaction. Though, metal catalysts have significant advantages in asymmetric synthesis over the organic molecules as wide substrate scope with catalytic acivity, they offer some troubles also such as potential heavy metals high price, toxicity, pollution, waste treatment, etc. On the other hand, metal free organocatalytic reactions unlike metal-ligand complexes, generally tolerate aerobic conditions and do not require rigorous exclusion of water. They enjoy a broad spectrum of substrates than enzymes and can be used in various organic solvents. Thus the development of enantioselective organocatalysts is one of the most challenging and formidable endeavors in modern science and technology. This chapter also details a brief review on reactions of p-benzoquinones and domino reactions. Benzoquinones are versatile intermediates in organic synthesis. Owing to functionalities such as enone, p-benzoquinones undergo Diels-Alder reactions and [3+2] cycloaddition reactions. These cross conjugated deienones can be utilized for the synthesis of carbocyclic and heterocyclic ring systems. in Abstract CHAPTER-2: Synthesis and Charaterization of Novel Camphorsulfonamide-based Prolinamide oreanocatalysts This chapter deals with synthesis and characterization of novel camphor-based prolinamide organocatalysts. Chiral monoterpene such as camphor, known to be used in several medicines antiseptics and insecticides having rigid bicyclic structure are widely used synthons in asymmetric synthesis. Camphor and its derivatives can afford a simple, inexpensive scaffold around which to build a chiral catalyst. Such molecules arouse our attention to use these molecules as chiral scaffold to develop proline-based chiral organocatalysts for asymmetric synthesis. For this purpose we synthesized camphor and proline based organocatalysts as shown in figure 1...................