Catalytic Asymmetric Inverse‐Electron‐Demand Oxa‐Diels–Alder Reaction of In Situ Generated <i>ortho</i>‐Quinone Methides with 3‐Methyl‐2‐Vinylindoles

By selecting 3-methyl-2-vinylindoles as a class of competent dienophiles, this approach provides an efficient strategy to construct an enantioenriched chroman framework with three adjacent stereogenic centers in high yields and excellent stereoselectivities.

Abstract

The first catalytic asymmetric inverse-electron-demand (IED) oxa-Diels-Alder reaction of ortho-quinone methides, generated in situ from ortho-hydroxybenzyl alcohols, has been established. By selecting 3-methyl-2-vinylindoles as a class of competent dienophiles, this approach provides an efficient strategy to construct an enantioenriched chroman framework with three adjacent stereogenic centers in high yields and excellent stereoselectivities (up to 99 % yield, >95:5 d.r., 99.5:0.5 e.r.). The utilization of ortho-hydroxybenzyl alcohols as precursors of dienes and 3-methyl-2-vinylindoles as dienophiles, as well as the hydrogen-bonding activation mode of the substrates met the challenges of a catalytic asymmetric IED oxa-Diels-Alder reaction.