Efficient Two-Step Conversion of α,β-Unsaturated Aldehydes to Optically Active γ-Oxy-α,β-unsaturated Nitriles and Its Application to the Total Synthesis of (+)-Patulolide C

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Abstract
An efficient two-step conversion of α,β-unsaturated aldehydes into optically active γ-oxy-α,β-unsaturated nitriles is described. First, catalytic asymmetric cyanation−ethoxycarbonylation using (S)-YLi3tris(binaphthoxide) (YLB) afforded chiral allylic cyanohydrin carbonate. Second, a [3,3]-sigmatropic rearrangement proceeded without racemization under thermal conditions to give γ-oxy-α,β-unsaturated nitriles. Lewis acids were also effective for the rearrangement, and the reaction proceeded smoothly under mild conditions. To demonstrate the utility of the conversion, concise catalytic enantioselective total synthesis of (+)-patulolide C was performed.