| In this thesis, we have synthesized and characterized a series of chiral NCN pincer Rh(III) complexes with bis(imidazolinyl)phenyl ligands. All these pincer rhodium complexes have been successfully applied to catalyze asymmetric alkynylation reactions of 1,3-diynes and ethyl or methyl trifluoropyruvates.1. Synthesis and characterization of chiral NCN pincer Rh(III) complexes with bis(imidazolinyl)phenyl ligands.Starting from commercially available isophthaloyl dichloride, 5-nitroisophthalic acid or 5-(tert-butyl)isophthalic acid, we have synthesized a series of chiral bis(imidazolinyl)phenyl ligands(Phebim) 5 after a three-step sequence.(Scheme 1) Then the ligands coordinates with rhodium source(from triply hydrated rhodium trichloride) via C-H bond activation, affording the corresponding chiral pincer Rh(III) choloride complexes(Phebim-Rh-Cl) 6. Subsequently, the pincer rhodium choloride complexes 6 react with excess silver acetate in dichloromethane, and convert to final products pincer rhodium acetate complexes 1. Additionally, complexes 1a-1c and(-)-1a-(-)-1c are enantiomers respectively. All these achieved new compounds have been fully characterized and by 1HNMR, 13 CNMR and high resolution mass spectrum(new metal complexes 6 and 1 have been characterized by elemental analysis instead). The characterization data have been analyzed to confirm the structures.2. The asymmetric alkynylation of 1,3-diynes with trifluoropyrates.We have explored the catalytic performance of the pincer Rh(III) complexes(Phebim-Rh-OAc) in the asymmetric alkynylation of 1,3-diynes with trifluoropyrates. Under the optimized conditions, we have extended 21 substrates. Optically active propargylic alcohols substituted by trifluoromethyl were prepared successfully with up to 99% yields and up to 99% ee values(Scheme 2). We have furnished two of the catalytic products and got the crystals of them to confirm their absolute configurations by X-ray diffraction analysis. The reactions catalyzed by 1a-1c and(-)-1a-(-)-1c give products with opposite absolute configurations. All these new compounds have been characterized by 1HNMR, 13 CNMR and high resolution mass spectrum to confirm their structures. |
