不对称三烯胺催化的发展

The Development of Asymmetric Trienamine Catalysis

手性胺可以与多不饱和羰基化合物原位生成三烯胺中间体,其给电子效应根据插烯规则可通过共轭不饱和体系传递,进而提高三烯胺体系的HOMO能量,并能够在远端β,ε-或δ,ε-位与多种缺电子烯烃发生Diels-Alder环加成反应。采用这种合成策略,可以制备许多结构多样和复杂的环状手性化合物。这种策略除了能够高效地在羰基化合物远端直接实现官能团化,更重要的是ε-反应位点即使距离催化剂手性中心达七个键之远,仍能获得优秀的立体选择性控制,这在不对称合成中具有重要的研究价值。本文将总结近年来不对称三烯胺催化机制的发现及发展,重点介绍2,4-二烯醛、多种二烯酮、含羰基芳香化合物经由三烯胺、交叉共轭三烯胺或形式三烯胺进行的不对称反应,并对手性胺催化的进一步应用进行展望。

A chiral amine catalyst can generate polyconjugated trienamine intermediates with polyunsaturated carbonyl compounds. As such, the electron-donating property of the amine catalyst can be transmitted along the C=C bonds, raising the HOMO energy of the polyconjugated enamine systems. As a result, highly asymmetric Diels-Alder cycloaddition reactions with a variety of electron-deficient alkenes could occur at the remote β, ε- or δ, ε-positions of trienamines, which can efficiently produce a wide range of chiral cyclic substances with highly structural diversity and complexity. This catalytic strategy not only successfully realizes the direct functionalizations of carbonyl compounds at the remote ε-position, but also excellent diastereo- and enantioselectivity could be obtained even though the reactive ε-site is seven bounds away from the chiral center of amine catalyst. In this respect, this catalytic protocol is of great usefulness and importance in organic synthesis because the related compounds are hard to be prepared using the conventional methods. In the review, we summarize the discovery and the development of asymmetric trienamine catalysis over the past few years, with emphasis on the asymmetric reactions of 2, 4-dienals, various types of dienones, and aromatic compounds specifically functionalized with a carbonyl group, via trienamine, cross-conjugated trienamine or formal trienamine catalysis. In addition, the future development of chiral amines is also discussed.