Carbon-carbon bond formation is one of the most important reactions in synthetic chemistry. In this thesis, with the aid of DFT calculations, mechanistic studies of different types of C–C bond formation reactions via organo- and metallo-catalysis were reported. In Chapter 2, indole C–H activations both at the C6 position and on a CH₃ substituent at the C2 position enabled by phosphoric acid were investigated. A kinetic-thermodynamic control scenario between the N1- and C6-alkylation was confirmed. For the indole C(sp³)–H activation, the initial instalment of the electrophile was found to be imperative for further transformations. Chapter 3 was about the cross-dehydrogenative coupling of 4-phenoxyl-2-coumarin. A novel double concerted-metalation-deprotonation mechanism was supported. The...[ Read more ]

Carbon-carbon bond formation is one of the most important reactions in synthetic chemistry. In this thesis, with the aid of DFT calculations, mechanistic studies of different types of C–C bond formation reactions via organo- and metallo-catalysis were reported. In Chapter 2, indole C–H activations both at the C6 position and on a CH₃ substituent at the C2 position enabled by phosphoric acid were investigated. A kinetic-thermodynamic control scenario between the N1- and C6-alkylation was confirmed. For the indole C(sp³)–H activation, the initial instalment of the electrophile was found to be imperative for further transformations. Chapter 3 was about the cross-dehydrogenative coupling of 4-phenoxyl-2-coumarin. A novel double concerted-metalation-deprotonation mechanism was supported. The C3–H of coumarin is activated first followed by the phenyl C–H. In Chapter 4, the origin of site-selective C–H bond cyanation enabled by Cu catalyst was studied. On the basis of experimental evidence and theoretical calculations, a Cu-bound N centered radical was found to exhibit amplifying effect during hydrogen atom transfer process. Chapter 5 was about the mechanism of iron-catalyzed 1,4-selective hydrovinylation with unactivated alkenes. Detailed mechanistic studies were performed, and the reaction was found to be enabled via the interplay between different spin states of catalyst. Chapter 6 provides summary of each chapter as well as future perspective.