Connective synthesis of polysubstituted tetrahydropyrans by a novel and stereocontrolled metallo-ene/Intramolecular Sakurai Cyclization sequence.

A novel methodology based upon the allylmetalation step followed by an Intramolecular Sakurai Cyclization (IMSC) provides an efficient access to a variety of tetrahydropyran derivatives. This new strategy nicely complements our initial protocol that embodied a tandem ene reaction/IMSC sequence. Both mono- and dihydroxy-tetrahydropyrans could be easily assembled with complete stereocontrol at the various chiral centers.