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。
Normal alkyl sp3 C―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 sp3 C―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 sp3 C―H bonds,without the assistance of directing groups have been rarely investigated.This review focuses on the functionalization of normal alkyl sp3 C―H bonds,such as methyl and primary sp3 C―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 dehyd
作者
赵梦迪
陆文军
ZHAO Mengdi;LU Wenjun(Department of Chemistry,Shanghai Jiao Tong University,Shanghai 200240,P.R.China.)
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2019年第9期977-988,共12页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(21372153)资助项目~~
关键词
烷烃
C―H活化
官能化
选择性
过渡金属
Alkane
C―H activation
Functionalization
Selectivity
Transition metal
