Explorative studies towards the synthesis of biocogically active carbocyclic and heterocyclic systems

Abstract

Beginning from the summer days of 2018, it took nearly five long years for me to finish the research work incorporated in this thesis entitled “EXPLORATIVE STUDIES TOWARDS THE SYNTHESIS OF BIOLOGICALLY ACTIVE CARBOCYCLIC AND HETEROCYCLIC SYSTEMS”. The work is mainly focused on development of efficient and environment benign methodologies for the synthesis of carbocyclic and heterocyclic compounds. The entire work depicted in this thesis has been divided into five chapters. In the beginning, Chapter I deals with a brief review on the development of novel reaction protocols for the transformation reaction on carbocyclic and heterocyclic compounds. These compounds have extensively been used in the designing of various pharmaceutically significant compounds. Apart from this, they are considered to be powerful building blocks for the construction of biologically active compounds. In Chapter II bio-based, environmental benign media ethyl lactate was used in synthesis of verities of unsymmetrical azobenzenes. The methodology proceeds without the use of toxic transition metal catalyst and avoids harsh reaction conditions. A green methodology is thus reported with synthesis of good yield of the product. In Chapter III a very simple, efficient and environment benign protocol for the synthesis of diverse array of 2,3-dihydroquinazolin-4(1H)-ones using wide range of aldehydes, isatoic anhydride with ammonium acetate was described. Eucalyptol, a bio-degradable solvent was used in this methodology which itself acted as a catalyst thus avoiding the use of toxic metals or hazardous materials. The activity of this bio-based reaction medium, eucalyptol was further extended towards the synthesis of isoxazolone derivatives using wide range of aldehydes, ethyl acetoacetate and hydroxyl amine hydrochloride. In Chapter IV synthesis of 1-amidoalkyl-2-naphthol and 1-thioamidoalkyl-2-naphthol is discussed. These derivatives carry great importance now a day as because they can easily be transformed to biologically potent heterocyclic entities via hydrolysis of amidic groups. In this chapter humic acid has been explored as catalyst with the association of operational simplicity of the method, mild reaction conditions, shorter reaction time. By this process, good yield of desired product 1-amidoalkyl-2-napthol is obtained by using aldehyde, β- napthol and acetamide. And 1-thioamidoalkyl-2-napthol is also prepared by using aldehyde, β-napthol and thioacetamide. In Chapter V inexpensive, environmental benign catalyst boric acid was used in synthesis of verities of bis-lawsones. The methodology proceeds without the use of toxic metal catalyst and avoids harsh reaction conditions. A green methodology is thus reported with synthesis of good yield of the product by reacting lawsone with wide range of aldehydes.