Mechanism of Copper Catalyzed Diazo Coupling and its Applications & Reactions of Multiynes
thesisposted on 21.07.2015, 00:00 by Phani Raja P. Mamidipalli
This thesis has two main parts. Part I is composed of two chapters which describes mechanistic investigation of copper catalyzed reactions of diazo compounds followed by their applications in click chemistry. Part II consists of three chapters describing new methods for the generation of functionalized arenes from multiynes via transition metal catalyzed reactions. Chapter 1 consists of the mechanistic study of copper catalyzed reaction of diazo compounds with terminal alkynes. In this work, with the help of kinetic preference of the catalyst, crossover experiments data and hammett plots, we gathered substantial evidence for the copper acetylide mechanism over the Cu-carbenoid-mediated C–H insertion mechanism for the reaction between terminal alkyne and diazo compounds with CuI. Chapter 2 describes a novel three component coupling reaction for the preparation of 1,4,5-trisubstituted-1,2,3-triazoles by in-situ trapping of 5-copper-1,2,3-triazole intermediate with diazo compounds. Selected examples are highlighted to demonstrate the scope of the reaction along with the electronic effects of the alkyne and azides on the three component coupling reaction. This methodology is further extended for the preparation of fused triazole motifs in a single step. In part II, chapter 3 discuss a brief survey in the recent developments of HDDA based aryne chemistry and its applications. Chapter 4 discloses an unprecedented dual reactivity of C–H bonds on the -carbon of the silyl group in the aryne intermediates. In this 2° and 3° C–H bonds to the silicon exclusively undergoes 1,5-hydride transfer, whereas aryne 1° C–H bonds were participated in the insertion reaction. This dichotomy of the reaction is supported by the DFT calculations. Extension of this work on the sp2 C–H insertion reaction provides us a new methodology for the preparation of biaryl moieties from the alkyne building blocks. Finally, in chapter 5 we disclose conceptually distinctive method and new benzannulation reaction to generate functionalized arynes from triynes. By using this silyl substituted triynes, we prepared pharmaceutically important functionalized aryl trifluoromethylthio compounds Ar-SCF3 from aliphatic starting materials.