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Catalytic Enantioselective Allylation of Dienals
P. Zhang, J. P. Morken*
Boston College, Chestnut Hill, USA
20 November 2009 (online)
The authors describe nickel-catalyzed 1,2-allylation of α,β,γ,δ-unsaturated aldehydes using allylboronic acid pinacol ester. This transformation is believed to proceed via an unsaturated π-allyl complex 1 which undergoes 3,3′-reductive elimination; this mechanistic scheme explains the fact that simple enones are unreactive under the reaction conditions. Inversion of the α,β-double bond configuration is a remarkable feature of the described method. Under optimized conditions the protocol was applied to a number of substrates with various δ-substituents, which gave the corresponding products with good yields (75-92%) and high enantioselectivities (73-94% ee). The developed procedure can provide rapid buildup of molecular complexity.