Catalytic asymmetric β,γ activation of α,β-unsaturated γ-butyrolactams: direct approach to β,γ-functionalized dihydropyranopyrrolidin-2-ones.

Skeleton in the closet: The title reaction enables the development of the first catalytic β,γ-selective Diels-Alder [4+2] annulation of α,β-unsaturated γ-butyrolactams (see scheme; Boc=tert-butoxycarbonyl, Ts=4-toluenesulfonyl). This process provides a direct method for the enantioselective construction of bi- or tricyclic dihydropyranopyrrolidin-2-one skeletons in only one step.