Enantioselective Synthesis of Fused Butyrolactones via Organocatalytic Formal [2 + 2 + 2] Annulation of γ-Butenolides, Methylene Indolinones, and Nitroolefins.

An organocatalyzed asymmetric synthesis of fused butyrolactones via formal [2 + 2 + 2] annulation between γ-butenolides, methylene indolinones, and nitroolefins in a one-pot process has been established. Products containing six contiguous stereocenters could be obtained in good yields (up to 95%) with excellent enantioselectivities (up to &gt;99% ee) catalyzed by a l-<i>tert</i>-leucine-derived bifunctional thiourea catalyst.