Inexpensive Metals-Catalyzed/Mediated Tandem Cyclization Of 1,6-diynes

Cyclic compounds are widely found in natural products,pharmaceutical molecules,and functional materials.The tandem cyclization of 1,6-diynes is one of the most efficient protocols for the construction of polycyclic compounds.These reactions are generally catalyzed by noble metal complexes such as ruthenium,rhodium,and palladium complexes.Non-noble metal-catalyzed/mediated tandem cyclization of 1,6-diynes has been less studied.N-Heterocyclic carbenes(NHCs)are strong a-coordination heterocyclic ligands and translation metal complexes of NHCs have wide important applications in catalysis,medicine and materials.In this thesis,we describe non-noble metal initiated cyclization of 1,6-diynes and the synthesis and characterization of rhodium-NHC complexes,major progresses are presented.1.Manganese-catalyzed sequential annulation between indoles and 1,6-diynesMn(CO)5Br-catalyzed selective annulation reaction between 1-(pyridin-2-yl)-1H-indoles and 1,6-diynes under oxidative condition is described.A number of fused carbazole derivatives were obtained in moderate to good yields.This reaction involves the construction of three C-C bonds in one-pot through C-H bond activation,alkyne insertion,and oxidative dehydrogenation.It offers an efficient protocol to prepare fused carbazole compounds using cheap metal catalyst and easily available materials2.Synthesis of cyclic gem-dinitro compounds via radical nitration of 1,6-diynesNitration of 1,6-diynes was studied,and a number of cyclic gem-dinitro compounds were selectively obtained in high yields.The reaction proceeds at room temperature using cheap and relatively safe nitrating agent Fe(NO3)·9H2O.A number of gem-dinitro compounds and nitro-substituted indenes were obtained in moderate to good yields.The regioslectivity is determined by the stability and activity of the alkenyl radical intermediates.The reaction offers an easy and convenient protocol to prepare gem-dinitro compounds,which are not easily obtained via the known procedures.3.Unbridged Rh(Ⅱ)-Rh(Ⅱ)complexes of N-heterocyclic carbenes and their reactionsA few dimeric Rh(Ⅱ)-Rh(Ⅱ)complexes supported by NHC ligands with an unsupported Rh-Rh bond and dirhodium-NHC peroxide complexes were prepared.The structures of the dimeric rhodium(Ⅱ)complexes consist of two rhodium ions in octahedron geometry,which are bound together by an unsupported Rh(Ⅱ)-Rh(Ⅱ)bond.The structurally characterized dirhodium(Ⅲ)(μ-η1:η1-O2)complexes are formed via the insertion of one molecule of O2 into the Rh-Rh bonds in the presence of monodentate phosphorus ligands.Such a reaction has not been known for Rh(Ⅱ)-Rh(Ⅱ)complexes supported by NHC ligands.