Chen Ye-Wei, Liu Yang, Lu Han-Yu, Lin Guo-Qiang, He Zhi-Tao
CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Shanghai, China.
School of Physical Science and Technology, ShanghaiTech University, Shanghai, China.
Nat Commun. 2021 Sep 24;12(1):5626. doi: 10.1038/s41467-021-25978-6.
Transition metal-catalyzed asymmetric allylic substitution with a suitably pre-stored leaving group in the substrate is widely used in organic synthesis. In contrast, the enantioselective allylic C(sp)-H functionalization is more straightforward but far less explored. Here we report a catalytic protocol for the long-standing challenging enantioselective allylic C(sp)-H functionalization. Through palladium hydride-catalyzed chain-walking and allylic substitution, allylic C-H functionalization of a wide range of acyclic nonconjugated dienes is achieved in high yields (up to 93% yield), high enantioselectivities (up to 98:2 er), and with 100% atom efficiency. Exploring the reactivity of substrates with varying pK values uncovers a reasonable scope of nucleophiles and potential factors controlling the reaction. A set of efficient downstream transformations to enantiopure skeletons showcase the practical value of the methodology. Mechanistic experiments corroborate the PdH-catalyzed asymmetric migratory allylic substitution process.
过渡金属催化的、底物中带有适当预存离去基团的不对称烯丙基取代反应在有机合成中被广泛应用。相比之下,对映选择性烯丙基C(sp)-H官能化反应更为直接,但研究却少得多。在此,我们报道了一种用于长期以来具有挑战性的对映选择性烯丙基C(sp)-H官能化反应的催化方法。通过氢化钯催化的链行走和烯丙基取代反应,多种无环非共轭二烯的烯丙基C-H官能化反应得以实现,产率高(高达93%)、对映选择性高(高达98:2的对映体过量)且原子利用率达100%。研究具有不同pK值的底物的反应活性,揭示了亲核试剂的合理范围以及控制反应的潜在因素。一系列向对映纯骨架的高效下游转化展示了该方法的实用价值。机理实验证实了PdH催化的不对称迁移烯丙基取代过程。