Diastereoselective construction of tetracyclic chromanes via a triply annulative strategy

A triple Michael/aldol cascade reaction has been established to construct tetracyclic chromanes in a diastereoselective fashion (≥5 : 1 dr). The polycyclic products were generated in 50–78% isolated yields under mild and metal-free conditions. Five reactive sites of enolate-tethered divinyl ketones were sequentially utilized to form four C–C bonds in a one-pot operation, leading to a construction of three new rings. Up to six consecutive stereocenters, including two quarternary stereogenic centers, were created in this domino process.