四川大学华西药学院陈应春团队报道了π-Lewis碱催化的环戊二烯酮和环庚三烯酮的不对称乙烯基多旋反应。相关研究成果发表在2021年10月7日出版的《德国应用化学》。

研究人员发现4-羟基-2-环戊烯酮的碳酸盐可以形成π-烯丙基钯基1,2-碳偶极子，其将异构化为有趣的η2-Pd(0)-环戊二烯酮络合物。与不稳定母体环戊二烯酮相比，通过Pd(0)作为π-Lewis碱的后键，相关η2-络合物的HOMO能显著提高，使得未配位的C=C键在与各种1-氮杂二烯的逆电子需求氮杂二烯-阿尔德型反应中作为电子丰富的亲二烯。在捕获重新生成的π-烯丙基钯物种后，乙烯基（aza）Morita–Baylis–Hillman或交叉Rauhut–Currier分别与（亚胺）羰基或活性烯烃加成，分别提供手性[4+2]或[2+2]环加合物。

研究人员开发了一种新的来自简单的手性源的C 1对称配体，通过一个不寻常的动态动力学拆分过程，即使与外消旋底物也表现出很高的立体选择性。此外，环庚三烯酮也可以被Pd(0)络合物激活。

附：英文原文

Title: π-Lewis Base-Catalyzed Asymmetric Vinylogous Umpolung Reactions of Cyclopentadienones and Tropone

Author: Ying-Chun Chen, Xing-Xing Yang, Ru-Jie Yan, Guang-Yao Ran, Chen Chen, Jing-Fei Yue, Xiao Yan, Qin Ouyang, Wei Du

Issue&Volume: 2021-10-07

Abstract: We disclosed the carbonates of 4-hydroxy-2-cyclopentenones could form π-allylpalladium-based 1,2-carbodipoles, which would isomerize to interesting η  2  -Pd(0)-cyclopentadienone complexes. Compared with the labile parent cyclopentadienone, the HOMO-energy of the related η  2  -complex was significantly raised via the back-bonding of Pd(0) as a π-Lewis base, rendering the uncoordinated C=C bond as an electron-richer dienophile in inverse-electron-demand aza-Diels–Alder-type reaction with diverse 1-azadienes. The vinylogous (aza)Morita–Baylis–Hillman or cross Rauhut–Currier addition to (imines)carbonyls or activated alkenes, respectively, was also realized to afford chiral [4+2] or [2+2] cycloadducts, respectively, after trapping the re-generated π-allylpalladium species. New C  1  -symmetric ligands from simple chiral sources were developed, exhibiting high stereoselectivity even with racemic substrates via an unusual dynamic kinetic resolution process. Besides, tropone could be similarly activated by a Pd(0) complex.

DOI: 10.1002/anie.202111708

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202111708