Research On AuNPore-Catalyzed Semihydrogenation Of Alkynes

Selective semihydrogenation of internal alkynes to form cis-alkenes is an important method for synthesis of fine chemicals, such as vitamine, aromatic, pharmaceutical, and pesticide et al. Compared with the C=C bond, the C=C bond is more active in the hydrogen-nation reaction. Therefore, a great challenge still remained in the semihydrogenation of alkynes. In the reduction process, the most important is to choose a suitable system.In this thesis, hydrogenation gas (H2) and gold nanoporous (AuNPore) were used as the hydrogen source and the catalyst, respectively, in the semihydrogenation of alkynes. Heterolytic cleavage of H2 to form a Au-H active species was achieved by using a nitrogen-containing coordinating solvent, and thereby the semihydrogenation of alkynes was success-fully achieved.Selective semihydrogenation of diphenylacetylene was chosen as the model reaction to screening the reaction conditions. The desired cis-alkene product was obtained in 93% yield with 100% selectivity under the optimized conditions:5 mol% AuNPore,1.0 MPa H2,5.0 mL Et2NH, at 90℃ for 16 h. Then evaluated the applicable scope of substrates under the optimized conditions, the desired cis-alkene products were obtained in 55%-98% yields with 100% selectivity.The results obtained indicated that the yields were influenced by the electronic property of substituents linked on the C=C group. A relatively high yield were obtained from the reactions of alkynes bearing electron-withdrawing goups. The catalyst AuNPore could be reused at least 5 times without loss of catalytic activity.