Ruthenium-catalyzed oxidative coupling/cyclization of isoquinolones with alkynes through C-H/N-H activation: Mechanism study and synthesis of dibenzoa,gquinolizin-8-one derivatives

摘要

The mechanism of {RuCl _2(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 Ru 0 sandwich complexes that undergo oxidation to regenerate the catalytically active Ru ~(II) complex with the copper oxidant and release the desired dibenzoa,gquinolizin-8-one derivatives. All of the relevant intermediates were fully characterized and determined by single crystal X-ray diffraction analysis. The {RuCl _2(p-cymene)} _2-catalyzed C-H bond functionalization of isoquinolones with alkynes to synthesize dibenzoa,gquinolizin-8-one derivatives through C-H/N-H activation was also demonstrated. All in the detail: A detailed study of the mechanism of the Ru ~(II)-catalyzed oxidative coupling/cyclization of isoquinolones with alkynes is reported (see scheme). All of the key stages were identified and intermediates were determined by X-ray crystallography. An efficient and highly regioselective {RuCl _2(p-cymene)} _2-catalyzed oxidative annulation of isoquinolones with alkynes to synthesize dibenzoa,gquinolizin-8- one derivatives with a broad substrate scope was also developed.