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Investigation and Comparison of the Mechanistic Steps in the [(Cp*MCl2)2] (Cp*=C5Me5; M=Rh, Ir)-Catalyzed Oxidative Annulation of Isoquinolones with Alkynes

Authors

  • Nuancheng Wang,

    1. State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (P.R. China), Fax: (+86) 22-2350-4781
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  • Prof. Dr. Bin Li,

    Corresponding author
    1. State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (P.R. China), Fax: (+86) 22-2350-4781
    • State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (P.R. China), Fax: (+86) 22-2350-4781
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  • Prof. Dr. Haibin Song,

    1. State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (P.R. China), Fax: (+86) 22-2350-4781
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  • Prof. Shansheng Xu,

    1. State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (P.R. China), Fax: (+86) 22-2350-4781
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  • Prof. Dr. Baiquan Wang

    Corresponding author
    1. State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (P.R. China), Fax: (+86) 22-2350-4781
    2. State Key Laboratory of Organometallic Chemistry, Chinese Academy of Sciences, Shanghai 200032 (P.R. China)
    • State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (P.R. China), Fax: (+86) 22-2350-4781
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Abstract

The mechanism of the [(Cp*MCl2)2] (M=Rh, Ir)-catalyzed oxidative annulation reaction of isoquinolones with alkynes was investigated in detail. In the first acetate-assisted C[BOND]H-activation process (cyclometalated step) and the subsequent mono-alkyne insertion into the M[BOND]C bonds of the cyclometalated compounds, both Rh and Ir complexes participated well. However, the desired final products, dibenzo[a,g]quinolizin-8-one derivatives, were only formed in high yield when the Rh species participated in the final oxidative coupling of the C[BOND]N bond. Moreover, a RhI sandwich intermediate was isolated during this transformation. The iridium complexes were found to be inactive in the oxidative coupling processes. All of the relevant intermediates were fully characterized and determined by single-crystal X-ray diffraction analysis. Based on this mechanistic study, a RhIII→RhI→RhIII catalytic cycle was proposed for this reaction.

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