Catalytic Asymmetric [3 + 2] Cycloaddition of Exocyclic Enol Ethers for the Synthesis of Spiroketals

Abstract

High Resolution Image Download MS PowerPoint Slide An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric [3 + 2] cycloaddition of exocyclic enol ethers with p -quinones was achieved. The transformation was enabled by a chiral N, N ′-dioxides/Tm III complex as the Lewis acid catalyst and afforded a series of enantiomerically enriched benzannulated spiroketal derivatives in good yields (up to 99%) and enantioselectivities (up to 98% ee). Topographic steric maps and distribution of the buried volumes of the catalysts via Cavallo’s SambVca 2 tool were used to elucidate the enantioinduction raised by the ligands and the metal ions.

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