Investigation of graphene oxide and Au based monometallic and alloy nanoparticles as nanocatalysts for coupling and oxidative organic transformations

Abstract

The development of green and sustainable chemical processes towards meeting the increasing demands of synthetic functional materials, while balancing the rapidly depleting natural resources has been a key focus area of research activities. Nanoparticles have attracted bulk of the interest towards the development of heterogeneous catalytic systems due to their large surface to volume ratio, tunable catalytic properties by controlling the structural and compositional complexities, possibilities of surface functionalization as required and stabilization of various active catalytic agents (such as free radicals, enzymes etc.) on their surface.The objective of this thesis is to explore the inherent catalytic activity of an important carbonaceous material graphene oxide and Au based monometallic and alloy nanoparticles towards the development of greener and highly efficient synthetic methods for useful organic transformations. The rationale for these studies is to exploit the structural and compositional intricacies of the nanoparticles for catalytic organic reactions with high activity, selectivity, atomefficiency and step-efficiency.In this direction, we have developed the following nanocatalytic systems for various important organic transformations under mild reaction conditions: 1) Graphene oxide based metal-free carbocatalytic system for multicomponent coupling reactions under solvent free condition. 2) Self-assembled monolayer coated gold nanoparticles through thiol binding which catalyze the aerobic oxidation of aryl substituted α-hydroxy ketones to aryl 1,2-diketones as well as one-pot synthesis of quinoxalines via in situ oxidation of α-hydroxy ketones and subsequent condensation with aryl 1,2-diamines in water.3) Bimetallic AuPd nanoparticle catalyzed selective oxidation of α-hydroxy esters and phosphonates as well as aerobic oxidative cross-dehydrogenative coupling for the synthesis of α-ketamide. 4) Aerobic Oxidative cross-dehydrogenative C-C coupling reaction catalyzed by shape controlled Au-Pd bimetallic Nanoparticles. The thesis is divided into the following chapters based on nanocatalytic systems used for various organic transformations.