TEMPO Catalyzed Oxidative Synthesis Of2-Aryl Quinazolines

This thesis deals with the studies on nitroxide-mediated heterocycle synthesis. It consists of two chapters:In the first chapter, the history and recent progress on TEMPO-mediated organic reactions and synthesis are briefly reviewed. The synthesis and physical properties of TEMPO are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis.In the second chapter, we report a novel and efficient method for the tandem oxidative synthesis of2-aryl quinazolines via sp3C-H amination using the TEMPO (2,2,6,6-tetramethylpiperidine N-oxyl radical) radical as the catalyst and oxygen as the terminal oxidant by a one-pot reaction of aryl methanamines with2-aminobenzaldehydes and2-aminobenzoketones, respectively. Although aminoxyl radical TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl radical) has been proved to be a powerful promoter for aerobic oxidation of alcohols, its application in C-H bond activation/functionalization and synthesis of heterocycles is rarely reported. Direct oxidative carbon hydrogen bond (C-H) activation/functionalization has received great attention for the facile formation of C-C/C-hetero bonds. However, most of this chemistry involves the use of transition metals as both the catalyst and the oxidant, and the C-H bond activation/functionalization under transitional metal-free conditions is much less explored. This chemistry provides an efficient and sustainable chemical process to synthesis of such heterocyclic compounds under metal-free and additive-free conditions. In addition, a mechanistic proposal is made on the basis of the kinetic isotope effects studies and isolation of the reaction intermediate1,2-dihydroquinazoline.