NHC-Catalyzed Enantioselective Synthesis of Tetracyclic δ-Lactones by (4 + 2) Annulation of -Quinodimethanes with Activated Ketones.

The N-heterocyclic carbene (NHC)-catalyzed generation of -quinodimethanes (-QDMs) from 9-fluorene-1-carbaldehydes followed by the interception with activated ketones resulting in the enantioselective synthesis of tetracyclic δ-lactones is presented. High diastereoselectivity of products, remote C(sp)-H functionalization, broad substrate scope, and mild reaction conditions are the notable features of the present (4 + 2) annulation.