Study On The Mechanism Of Hydrogenation Catalyzed By Rhodium Complex

The activation of C-H bond is an effective way for the concise construction ofC-C, C-N and C-O bonds, which plays an important role in the organicsynthesis. In the past decades, intermolecular cyclization and transition metalcatalyzed C-H bond activation and functionalization have received greatattention and made great progress for their convenient, atom economical, thelow yield of addition reaction and satisfaction the green chemical concept. Theresearch of the mild Rhodium-catalyzed C-H activation and intermolecularannulation with allenes from the microscope level contribute to the knowledgeof catalytic reaction process. The explanation of experimental phenomena andthe revelation of the relationship between catalyst structure and catalyticactivity, which could provide theoretical guidance for the development of newand efficient catalyst with an importan theoretical and practical significance.In our dissertation of graduation, from the third to the fourth chapter twoexperimental reported transition metal Rh and Pd complexes catalyzedbenzamide and amino phenol with iodobenzene intermolecular annulationwere selected as our research object. We carried out a computational studybased on density functional theory (DFT) from the microscope level revealingthe reaction mechanism of catalytic activation，thus reveal the essence of thecatalysis in the process of N-H deprotation and C-H activation. The studygradually provide theoretical guidance for the synthesis of the more complexcompound.The valuable research work in this paper are summarized as follows:The reaction mechanism of mid Rhodium-catalyzed C-H activation andintermolecular annulation with allenes was investigated by density functionaltheory. The calculation results suggest that The study uncovers the origin ofC-H activation and reaction selectivity for the reaction. The whole reactionconducts in three stages as (1) C-H activation induced by Rh-catalystinteracting with benzamide derivatives,(2) allene carborhodation, and (3) the dissociation of the catalyst. The results indicate that the N-H deprotonation firstmakes the C-H activation more feasible. The reaction stereoselectivitydepends on the type of C=C of allene coordinating into the Rh center forreaction1a and2a. The trans insertion for allene terminal C=C bond into Rhcenter is the most favorable one. In addition, regioselectivity presented incarborhodation is controlled mainly by the steric hindrance effect for reaction1b and2b. The reaction mechanism of1c with2a is similar to1a and2a.Because OPiv group is replaced by OMe, OMe transfers from N to Rh directlywith a three-membered transition state. The stabilization effect presented inC=O bond of OPiv with a five-membered transition state is lost, so that thebarrier is much higher than that with OPiv group.These results have reference value for the research and design of new highefficient catalyst for C-H activation and intermolecular annulation reaction.