Mechanistic study on the Cp*iridium-catalyzed N-alkylation of amines with alcohols

作者：Zhao, Guo-Ming; Liu, Hui-ling^*; Huang, Xu-ri; Zhang, Dan-dan; Yang, Xue

来源：RSC Advances, 2015, 5(29): 22996-23008.

DOI：10.1039/c5ra02052b

• HIGHLY SELECTIVE HYDROAMINOMETHYLATION
• BORROWING HYDROGEN
• IR COMPLEX
• INTRAMOLECULAR HYDROAMINATION
• RUTHENIUM HYDRIDE
• ROOM-TEMPERATURE
• INTERNAL ALKENES
• SECONDARY AMINE
• BASIS-SETS
• SULFONAMIDES

DFT calculations have been performed to study the mechanism of the N-alkylation of amines with alcohols catalyzed by [Cp*IrCl2](2) (Cp* = eta(5)-C5Me5) in the presence of K2CO3. The energetic results show that this N-alkylation reaction proceeds via the hydrogen autotransfer mechanism and the catalytic cycle includes three sequential stages: (1) alcohol oxidation to produce aldehyde, (2) aldehyde-amine condensation to form an imine and (3) imine reduction to afford the secondary amine product. For stages 1 and 3, the most favorable pathways are the inner-sphere hydrogen transfer pathway under the catalysis of Cp*Ir(NHPh)Cl (C) and the inner-sphere hydrogen transfer pathway with KHCO3 as the proton donor. Thermodynamically, both stages 1 and 2 are endergonic, but stage 3 is highly exergonic. Thus stage 3 is the driving force for the catalytic cycle. The energetic span model has also been used to assess the catalytic cycle, and it is found that the turnover frequency-determining intermediate (TDI) and the turnover frequency-determining transition state (TDTS) are the 18e complex Cp*Ir(kappa(2)-CO3K)Cl (A) and the transition state BC-TS5i for beta-H elimination, respectively. The calculated turnover frequency (TOF), 4.68 h (-1), agrees with the experimentally determined TOF and, therefore, provides strong support for the proposed catalytic cycle.

• 出版日期2015
• 单位吉林化工学院; 吉林大学