摘要/Abstract

过渡金属催化是现代有机合成化学中精准构建化学键最重要的工具之一.有机小分子催化是21世纪初开始蓬勃发展的一个新兴研究领域.两者在不对称烯丙基化反应中的完美结合有意义地解决了该领域亲核试剂的普适性、立体选择性控制等挑战性问题.本文综述了过渡金属与有机小分子协同催化的不对称烯丙基化反应研究进展.按照不同的手性控制方式（过渡金属催化剂控制手性、有机小分子催化剂控制手性以及两者共同控制手性）对这些反应进行了梳理和总结，同时对代表性反应的机理以及该领域仍然存在的问题与未来发展进行了简单阐述.
关键词: 不对称烯丙基取代反应, 协同催化, 过渡金属催化, 有机催化
Transition metal catalysis is one of the most important tools to accurately forge chemical bonds in modern organic synthesis. Organocatalysis, a biomimetic catalysis usually with metal-free small organic molecules, is a relatively young research area that started to flourish at the beginning of this century. Catalytic allylic substitutions are a kind of versatile reactions in organic chemistry; the combination of transition metal catalysis and organocatalysis in these reactions not only significantly expands the scope of nucleophiles, but also helps to resolve the stereocontrol issues. This paper will summarize the advance in the field of catalytic asymmetric allylic substitutions through synergetic transition metal-and organocatalysis. According to the source of chirality, these advances will be classified to three types. The first type is the catalytic asymmetric allylic substitutions induced by chiral transition metal catalysts. For these reactions, chiral ligands, including phosphine ligands and hybrid P, N ligands, have been used to achieve the high enantioselectivity. The non-chiral organocatalysts, such as pyrrolidine, Brønsted acids and boron reagents, were only used to activate the nucleophile or assist the generation of π-allyl metal intermediates. The second type is the catalytic asymmetric allylic substitutions induced by chiral organocatalysts. For the reaction of this type, various chiral organocatalysts, including chiral amines, chiral ureas and others, not only activate the substrates, but also control the enantioselectivity of allylic substitutions well through covalent and non-covalent bonds. Non-chiral ligands were only used to improve the catalytic capacity of transition metals. The last type is the catalytic asymmetric allylic substitutions induced by both of chiral transition metal catalysts and chiral organocatalyst. This strategy can not only realize the excellent stereo-control, but also achieve the challenging diastereo-diversity, if there exist continuous chiral centers. Overall, the joint utilization of transition metals and organocatalysts can achieve many significant asymmetric allylic substitutions that were previously difficult to realize through single transition metal catalysis. Meanwhile, the mechanism of representative transformations will be briefly introduced and at last, the prospective in this area will be given, such as simpler allylic sources and greener catalyst system.
Key words: asymmetric allylic substitution, synergetic catalysis, transition metal catalysis, organocatalysis


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