Ruthenium‐Catalyzed Oxidative Coupling/Cyclization of Isoquinolones with Alkynes through CH/NH Activation: Mechanism Study and Synthesis of Dibenzo[a,g]quinolizin‐8‐one Derivatives

• DOI: 10.1002/chem.201201862
• Publication Date: 2012-08-28T17:25:43Z
• Authors: Bin Li; Huiliang Feng; Nuancheng Wang; Jianfeng Ma; Haibin Song; Shansheng Xu; Baiquan Wang
• Keywords: Molecular Structure; Crystallography, X-Ray; Isoquinolines; 01 natural sciences; Catalysis; Ruthenium; 0104 chemical sciences; Cyclization; Alkynes; 0103 physical sciences; Organometallic Compounds; Oxidation-Reduction; Quinolizines

AbstractThe mechanism of [{RuCl2(p‐cymene)}2]‐catalyzed oxidative annulations of isoquinolones with alkynes was investigated in detail. The first step is an acetate‐assisted CH bond activation process to form cyclometalated compounds. Subsequent mono‐alkyne insertion of the RuC bonds of the cyclometalated compounds then takes place. Finally, oxidative coupling of the CN bond of the insertion compounds occurs to afford Ru0 sandwich complexes that undergo oxidation to regenerate the catalytically active RuII complex with the copper oxidant and release the desired dibenzo[a,g]quinolizin‐8‐one derivatives. All of the relevant intermediates were fully characterized and determined by single crystal X‐ray diffraction analysis. The [{RuCl2(p‐cymene)}2]‐catalyzed CH bond functionalization of isoquinolones with alkynes to synthesize dibenzo[a,g]quinolizin‐8‐one derivatives through CH/NH activation was also demonstrated.