Chin. J. Org. Chem. ›› 2007, Vol. 27 ›› Issue (05): 656-662. Previous Articles     Next Articles

Reports

溶剂对钯催化的叔丁基乙炔低聚反应化学选择性的调控作用

程金生*,a,b,赵进a,黄锁义a,江焕峰*,c   

  1. (a右江民族医学院基础医学院 百色 533000)
    (b中国科学院广州生物医药与健康研究院 广州 510665)
    (c华南理工大学化学科学学院 广州 510641)
  • 收稿日期:2006-01-04 修回日期:2006-08-03 发布日期:2007-05-10

Solvent-Controlled Chemoselective Palladium-Catalyzed Oligomerization of tert-Butyl Acetylene

CHENG Jin-Sheng*,a,b, ZHAO Jina, HUANG Suo-Yia, JIANG Huan-Feng*,c   

  1. (a School of Basic Medical Science, Youjiang Medical College for Nationalities, Baise 533000)
    (b Guangzhou Institute of Biomedicine & Health, Chinese Academy of Sci-ences, Guangzhou 510650)
    (c School of Chemistry Science, South China University of Technology, Guangzhou 510641)
  • Received:2006-01-04 Revised:2006-08-03 Published:2007-05-10

A novel solvent-controlled chemoselective palladium-catalyzed oligomerization of tert-butyl acetylene was reported in this paper. The reaction was carried out in benzene/n-BuOH binary solvent system smoothly. When benzene was preponderating component in the binary solvent system, a cyclotrimerization process occurred to give 1,3,5-tri-tert-butylbenzene via a mechanism of three acetylene molecular stepwise insertions forming σ-butadienyl-Pd and σ-hexatrienyl-Pd intermediates. While when the polar, protic and strong coordinating solvent, n-BuOH, which could help to cleave the C—Pd σ-bonds and solvate Pd(II) cation, Cu(II) cation, halo anion and σ-butadienyl-Pd inter-mediate etc., was increased to a certain ratio in the binary solvent system, the reaction proceed readily via n-BuOH promoted mechanism to give (3Z,5Z)-2,2,7,7-tetramethyl-3,6-dichloro-3,5-octadiene or (3Z,5Z)-2,2,7,7-tetramethyl-3,6-dibromo-3,5- octadiene, respectively, instead of cyclotrimerization product. Possible weak hydrogen bonds and n weak force between n-BuOH and tert-butyl acetylene (or σ-butadienyl-Pd intermediate) were also in favor of the n-BuOH promoted pathway. Mean-while, a coupling product 2,2,7,7-tetramethyl-3,5-octadiyne was given exclusively when the reaction was conducted in singular polar H2O. Influences of the solvent, catalysts, and possible mechanism were discussed.

Key words: tert-butyl acetylene, palladium, oligomerization, chemoselectivity, solvent