Studies on the C-C and C-N bonds formation via C-H bond functionalization using rhodium and IRIDIum catalysts

Abstract

Part 1. Rh-N-Heterocyclic Carbene(NHC) Catalyst Systems in C-H Functionalization2.Rh(NHC)-Catalyzed Direct and Selective Arylation of Quinolines at the 8-Position A new catalytic protocol for the regioselective direct arylation of quinoline derivatives at the 8-position has been developed. The reaction is catalyzed by a Rh(NHC) system, and the choice of the NHC ligand was most important for achieving high reactivity and selectivity.3. Rollover Cyclometalation Pathway in Rhodium Catalysis: Dramatic NHC Effects in the C-H Bond Functionalization Organometallic chelates are readily obtained upon coordination of metal species to multidentate ligands. Because of the robust structural nature, chelation frequently serves as a driving force in the molecular assembly and chemical architecture, and they are used also as an efficient catalyst in numerous reactions. Described herein is the development of a Rh(NHC) catalytic system for the hydroarylation of alkenes and alkynes with 2,2′-bipyridines (bipy) and 2,2′-biquinolines; the most representative chelating molecules. Initially generated (bipy)Rh(NHC) chelates become labile because of the strong trans-effect of N-heterocyclic carbenes, thus weakening a rhodium-pyridyl bond, which is trans to the bound NHC. Subsequent rollover cyclometalation leads to the C-H bond activation, eventually giving rise to double functionalization of chelate molecules. Density functional calculations are in good agreement with our mechanistic proposal based on the experimental data. The present study elucidated for the first time the dramatic NHC effects on the rollover cyclometalation pathway enabling highly efficient and selective bisfunctionalization of 2,2′-bipyridines and 2,2′-biquinolines.4. Ir(III)-Catalyzed Mild C-H Amidation of Arenes and Alkenes: An Efficient Usage of Acyl Azides as the Nitrogen Source Reported herein is the development of the Ir(III)-catalyzed direct C-H amidation of arenes and alkenes using acyl azides as the nitr...