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.