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CO2-activation for γ-butyrolactones and its application in the total synthesis of (±)-heteroplexisolide E.

An efficient nickel(0)-catalyzed highly regio- and stereoselective hydrocarboxylation of homopropargylic alcohols with ZnEt(2) in the presence of CO(2) (1 atm, balloon) to synthesize α-alkylidene-γ-butyrolactones is described. The catalyst is highly active and can be applied for the synthesis of (optically active) mono- or bicyclic α-alkylidene-γ-butyrolactones with excellent regio- and stereoselectivity and good functional group tolerance. The potential of the reaction has been demonstrated in the first synthesis of (±)-heteroplexisolide E.