Organocatalytic Asymmetric Synthesis of Functionalized 3,4‐Dihydropyran Derivatives

Organocatalysis can control both the chemo‐, diastereo‐ and enantioselectivity in the domino addition of 1,3‐cycloalkanediones to α,β‐unsaturated aldehydes providing optically active 3,4‐dihydropyrans (see scheme) with excellent enantioselectivies and good diastereoselectivities for a broad range of aryl‐ and aliphatic‐substituted α,β‐unsaturated aldehydes. The 3,4‐dihydropyrans were transformed to various important derivatives.