Studies Of Rhodium-catalyzed [6+2] Cycloaddition And Synthesis Of Chiral Ru-based Olefin Metathesis Complex

In recent years the transition-metal catalyst has been widely used in organicsynthesis as an efficient manner to prepare organic compounds, thereby attractingmany attentions. Especially, rhodium-metal complexes have played an increasinglyimportant role as its wide synthetic employment in carbon–carbon bond formationreactions. Rhodium-catalyzed cyclization/cycloaddition reactions, in particular, haveproven to be preferable in their ability to construct polycyclic carbo-andhetero-cycles. A rhodium catalyzed [6+2] cycloaddition of internal alkynes withcycloheptatriene is described. A series of substituted alkynes were cycloadded withcycloheptatriene through a [6+2] model to offer a variety of substituted bicycliccompounds in excellent yields. We found that the rhodium-catalyzed [6+2]cycloaddition underwent smoothly to give the corresponding ring products when[Rh(COD)Cl]2(5.0mol%) as the catalyst in combination with CuI (10mol%) asadditive and PPh3(10mol%) as ligand at120oC in xylene was selected as theoptimal catalytic system for the current transformation. Experimental data shows thatthe electronic effect as well as the steric hinders had significant effect on thecycloaddition reaction.What’s more, DFT calculations using Rh(I) model catalysthave also been carried out for further understanding of the mechanism.The olefin metathesis reaction was catalyzed by metal olefin complexes, alsoknown as metal carbene, on unsaturated carbon-carbon double bond or triple bond togive the products of carbon-carbon skeleton rearrangement reaction. As the Olefinmetathesis reactions undergo mild reaction conditions with high yield and almostindependent of the air and humid environments, and the vast majority of the organicgroups in the reaction need no protection, the reactoion has been attracting extensiveattention in recent years. The well-defined modern ruthenium catalysts had facilitatedthe application of this method in many fields, including polymer chemistry, organicsynthesis, and green chemistry and so on. Through the introduction of a large sterichindrance ligand in the chiral catalysts, we changed the steric hindrance of a chiralruthenium catalyst in order to improve the selectivity and activity of the catalyst.