Asymmetric Ketone Diene Coupling via Stereodivergent Copper Catalysis

We report herein the stereodivergent and enantioselective
coupling
of ketones with dienes. Under the developed conditions, the reactions
of 1,3-butadienyltriisopropylsilane with ketones provide syn-(E)-adducts with excellent enantioselectivities
via an α-silyl-(Z)-allylcopper intermediate.
By contrast, the reactions between 1,3-dienylboronate and ketones
involve an α-boryl-(E)-allylcopper intermediate
to give anti-(Z)-adducts with excellent
optical purity. The stereodivergence and enantioselectivity of the
reactions originate from the distinct allylcopper species involved
in the ketone addition step. DFT computational studies provide further
evidence to support the analyses.

本文报道了酮与二烯烃的立体发散性、对映选择性偶联反应。在优化得到的反应条件下，1,3-丁二烯基三异丙基硅烷与酮的反应，经由α-硅基-(Z)-烯丙基铜（α-silyl-(Z)-allylcopper）中间体，可生成具有优异对映选择性的顺式-(E)-加合物。与此相反，1,3-二烯基硼酸酯与酮的反应则通过α-硼基-(E)-烯丙基铜（α-boryl-(E)-allylcopper）中间体，得到光学纯度极佳的反式-(Z)-加合物。该反应的立体发散性与对映选择性，源于酮加成步骤中所涉及的不同烯丙基铜物种。密度泛函理论（DFT）计算研究为上述分析提供了进一步的佐证。