物理化学学报 >> 2019, Vol. 35 >> Issue (9): 977-988.doi: 10.3866/PKU.WHXB201811045

所属专题: 碳氢键活化

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普通烷烃C―H键的活化官能化

赵梦迪,陆文军*()   

  • 收稿日期:2018-11-30 录用日期:2019-01-15 发布日期:2019-01-18
  • 通讯作者: 陆文军 E-mail:luwj@sjtu.edu.cn
  • 作者简介:陆文军,1987年在华东化工学院获学士学位后,到中国科学院大连化学物理研究所工作八年。1997年在香港科技大学获硕士学位。1998年至2001年在日本九州大学,师从Yuzo Fujiwara教授获博士学位。随后在美国University of Colorado at Boulder跟随Josef Michl教授从事博士后工作近两年。现为上海交通大学化学系教授。一直从事惰性C—H键功能化反应以及高效、温和与环境友好的化学反应的研究工作
  • 基金资助:
    国家自然科学基金(21372153)

Alkanes Functionalization via C―H Activation

Mengdi ZHAO,Wenjun LU*()   

  • Received:2018-11-30 Accepted:2019-01-15 Published:2019-01-18
  • Contact: Wenjun LU E-mail:luwj@sjtu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21372153)

摘要:

普通烷烃C―H键是指不受杂原子和碳不饱和官能团影响的sp3C―H键,如甲烷、链烷烃和环烷烃的C―H键等。它们具有较大的键能和较小的酸碱性,因而呈现惰性,通常不易在温和条件下发生断裂。同时,除个别烷烃以外,普通烷烃往往具有不同性质和不同位置的C―H键,其反应选择性也是一个难点。近半个世纪以来,金属参与的惰性C―H键活化及官能化反应得到了重视与发展。其中,在没有官能团导向作用下,过渡金属催化剂对甲烷C―H键和普通烷烃一级C―H键进行选择性亲电活化和氧化加成,从而导致官能化反应发生是比较有效的。本文介绍了这些方法的研究进展,包含机理分析以及相关反应的建立。

关键词: 烷烃, C―H活化, 官能化, 选择性, 过渡金属

Abstract:

Normal alkyl sp3C―H bonds are ubiquitous in compounds such as methane, linear alkanes, and cycloalkanes that are not linked directly to heteroatoms or other functional groups. These unactivated bonds are not broken readily under mild conditions because their bond dissociation energy values are high and acidity values are low. Moreover, in the radical processes at high temperatures, reaction selectivity is not good for an alkane substrate with various alkyl sp3C―H bonds, which is commonly methyl < 1° < 2° < 3°. In the past five decades, C―H activation by transition-metal species to give C-metal bonds under mild conditions was intensively studied; all efforts were undertaken to provide new methods that can be applied in both chemical synthesis and chemical industry. However, the effective transformations of inert C―H bonds, particularly alkyl sp3C―H bonds, without the assistance of directing groups have been rarely investigated. This review focuses on the functionalization of normal alkyl sp3C―H bonds, such as methyl and primary sp3C―H bonds, via electrophilic activation or oxidative addition by using homogenous transition-metal catalysts, which are two main strategies in the study of inert C―H activation. The selectivity on C―H bond is methyl > 1° > 2° > 3° in both the reactions. Neither heterogeneous catalysis nor biocatalysis is mentioned in this review. Some remarkable progress is described on the study of reaction mechanisms and the establishment of novel reactions. For example, several selective oxidations of methane or linear alkanes have been introduced to afford new C―O, C―Cl, or even C―C bonds in the presence of Pt or Pd catalysts. The Shilov chemistry, which combines electrophilic activation of the C―H bond by the transition-metal complex, oxidation of the transition-metal intermediate, and nucleophilic substitution of organometallic species, has been emphasized in these reactions. Other transition-metal catalysts including Rh, Ir, Re, and W have been employed successfully in the carbonylation, borylation, and dehydrogenation of alkanes at moderate temperatures. The reaction pathways normally involve oxidative addition of the C―H bond with the transition-metal complex followed by insertion-elimination, reductive elimination, or β-H elimination. In the cascade reactions consisting of dehydrogenation of alkanes and addition of alkenes, new C―C or C―Si bonds can also be formed at terminal sites of linear alkanes. However, most of the above-mentioned reactions are still under investigation because of limited scope of the substrate, excess loading of the alkane, low efficiency of the catalyst, and high cost of the reaction operation. Breakthroughs in this promising field of alkane functionalization are possible when new concepts and technology are realized and applied.

Key words: Alkane, C―H activation, Functionalization, Selectivity, Transition metal

MSC2000: 

  • O643