摘要/Abstract

过渡金属催化的烯丙基取代反应是一类重要且实用的有机化学反应, 可以立体选择性地高效构建碳-碳键和碳-杂键. 可见光氧化还原催化可以利用绿色清洁的可见光能源在较为温和的条件下产生自由基或者自由基离子等高反应活性的反应中间体, 被广泛地应用于有机合成中, 逐渐发展成为一种重要的合成工具. 鉴于烯丙基取代反应的重要性, 过渡金属与光氧化还原协同催化的烯丙基取代反应逐渐引起化学家的兴趣. 该协同催化的策略可以实现单一过渡金属催化难以实现的烯丙基取代反应, 反应的区域选择性和立体选择性也体现出不同的特点, 有望发展成为单一金属催化的烯丙基取代反应的重要补充. 本文综述了近年来不同过渡金属与可见光氧化还原协同催化的烯丙基取代反应的研究进展.
关键词: 烯丙基取代反应, 过渡金属催化, 光氧化还原催化, 协同催化
Allylic substitutions catalyzed by transition metals are important and practical reactions, which can construct carbon-carbon bonds and carbon-heteroatom bonds efficiently and stereoselectively. Various transition metal catalysts, such as Pd, Ir, Cu, Ni, Rh and Ru, have been widely used in this reaction. To date, various “soft”, or stabilized nucleophiles (pKa<25), including malonates, acetoacetates and enolates, have been used in allylic substitutions. Conversely, the high reactivity of “hard”, or non-stabilized alkyl nucleophiles (pKa>25) has limited their utility in catalytic processes and their compatibility with functional groups. Visible light photoredox catalysis has been widely used in organic synthesis because it can generate high reactive intermediates, such as free radicals and radical ions, under mild conditions using green and clean energy, and has gradually developed into an important synthetic tool. Furthermore, merging photoredox catalysis with transition metal catalysts has become a popular strategy for expanding the synthetic utility of visible-light photocatalysis, and has led to the discovery of novel reaction modes. Due to the high activity of the intermediates in photoredox catalysis, the selectivity of these reactions, especially stereoselectivity, is still a challenge. In view of the importance of allyl substitutions, the allyl substitution co-catalyzed by transition metals and photoredox has attracted the interest of chemists. The synergistic strategy can realize allylic substitutions which are difficult to be achieved by single transition metal catalysis. The regioselectivity and stereoselectivity of these reactions also show different characteristics. It is expected to become an important complement to allylic substitution catalyzed by single metal. In this review, recent advances on allylic substitution co-catalyzed by different transition metals and photoredox are summarized. Meanwhile, the mechanism of representative transformations will be briefly introduced and the prospective in this area will be given.
Key words: allylic substitution, transition metal catalysis, photoredox catalysis, cooperative catalysis


PDF全文下载地址:

点我下载PDF