Synthesis Of The NNO-ruthenium Complexes And Their Catalytic Alkylations Of Indoles And Ketones With Alcohols

The alkylations of indoles and ketones with alcohols catalyzed by transition metal complexes have emerged as an important repertoire for the synthesis of structurally diverse indole derivatives and carbonyl compounds.The design of transition metal catalysts with high catalytic activity and selectivity to efficiently construct C-C bonds between indoles,ketones with alcohols to prepare indole and ketone derivatives with high added value is one of the research hotspot in the field of catalysis.Deprotonated bipyridyl alcohol ligands have multiple coordination sites and can form stable chemical bonds with metals.Ruthenium is often used in the development of highly active catalysts because of its various oxidation states.Combining the advantages of bipyridyl alcohol ligands and ruthenium can construct efficient and stable ruthenium complex.In addition,the catalytic activity of ruthenium complexes can be regulated by adjusting the steric and electronic effects of substituents on bipyridyl alcohol ligands.Based on this,a series of bipyridyl alcohol ligands were synthesized,and five Ru（II）complexes were obtained by reaction with[Ru（CO）₂Cl₂]_n.The catalytic properties of the series of ruthenium complexes for the alkylations of indoles and ketones with alcohols were investigated.The main work of this paper is as follows:1.In the presence of stoichiometric trimethylamine,bipyridyl alcohol ligands2-（C₅H₄N）-6-[CMe₂OH]C₅H₃N（L1H）、2-（C₅H₄N）-6-[CMe Ph OH]C₅H₃N（L2H）、2-（C₅H₄N）-6-[C（C₆H₅）₂OH]C₅H₃N（L3H）、2-（6-OMe C₅H₃N）-6-[CMe₂OH]C₅H₃N（L4H）、2-（6-OMe C₅H₃N）-6-[C（C₆H₅）₂OH]C₅H₃N（L5H）and[Ru（CO）₂Cl₂]_n reflux in tetrahydrofuran under the action of stoichiometric triethylamine,two Two-ligand and dinuclear chlorine-bridged ruthenium complexes Ru（L1）（CO）（μ-Cl）₂Ru（L1）（CO）（1a）、Ru（L2）（CO）（μ-Cl）₂Ru（L2）（CO）（1b）and three mononuclear ruthenium complexes Ru（L3）（CO）₂Cl（1c）、Ru（L4）（CO）₂Cl（1d）、Ru（L5）（CO）₂Cl（1e）were obtained.The five complexes were characterized by high resolution mass spectrometry and infrared spectroscopy.Moreover,the crystal structures of complexes 1c and 1e were determined by X-ray single-crystal determination.The results showed that 1c and 1e belonged to monoclinic system,with a spatial group type of P21/c,and the coordination environment of the central metal Ru is a twisted octahedron.2.The catalytic activity of complexes 1a-1c for the synthesis of bisindolylmethanes from indoles and alcohols was studied,and the possible mechanism of the reaction was explored.The results showed that 1a-1c exhibited good catalytic activity in the alkylation reaction.Among them,1c had the best catalytic performance,and the substrate scope of the catalytic system was wide.It was not only suitable for various primary alcohols,but also for aromatic secondary alcohols and aliphatic secondary alcohols.The isolation of products with yields up to94%.3.The catalytic activity of complexes 1a-1e for theα-alkylation of ketones was studied with PPh₃ as a co-catalyst,and the possible mechanism of the reaction was explored.The results showed that all the catalytic systems composed of 1a-1e and PPh₃ exhibited good catalytic activity in theα-alkylation of ketones.Among them,the catalytic system composed of 1e and PPh₃ had the best catalytic performance.The catalytic system was suitable for various ketones and aromatic alcohols.The yields of the products were 41-96%.