A Density Functional Theory Study of the Mechanism of Cu(II)-Catalyzed Synthesis of Pyrido[1,2-a]benzimidazoles

作者：Du Lijuan^*; Wu Caihong; Gu Honghong; Li Juan

来源：Chinese Journal of Organic Chemistry, 2015, 35(8): 1726-1732.

DOI：10.6023/cjoc201501034

• density functional theory(DFT)
• Cu(II)-Catalyzed
• C-N cross coupling
• mechanistic study

The reaction mechanism of Cu(II)-catalyzed synthesis of pyrido[1,2-a]benzimidazoles was theoretically investigated with the aid of density functional theory calculations (DFT) at the B3LYP level. Five possible mechanisms for the synthesis were proposed: (1) C-H-bond-breaking step preceding deprotonation of imino group, and finally C-N bond formation (Pathway a), (2) deprotonation of imino group preceding C-H-bond-breaking step, and finally C-N bond formation (Pathway b), (3) C-H-bond-breaking as the first step, then C-N bond formation preceding deprotonation of imino group (Pathway c), (4) the anti-imino-cupration mechanism (Pathway d), (5) the Friedel-Crafts alkylation mechanism (Pathway e). The calculation results indicate that the most favorable pathway involves C-H bond breaking by concerted metalation/deprotonation (CMD), followed by N-H deprotonation along the triplet state and C-N bond formation (Pathway a). A clear understanding of the reaction mechanism of pyrido[1,2-a]benzimidazoles formation should lead to more efficient synthetic strategies.

• 出版日期2015-8
• 单位暨南大学