Synthetic Studies on the MARDi Cascade: Stereoselective Synthesis of Heterocyclic Seven-Membered Rings

A versatile stereoselective synthesis of substituted and functionalized heterocyclic seven-membered rings is described. The approach involves a formal two-carbon ring expansion of heterocyclic cyclopentanones through a base-induced anionic domino three-component transformation named the MARDi cascade leading either to oxa-, aza-, or thiacycloheptanes bearing up to five contiguous stereogenic centers.