Stereoselective Quaternary Center Construction via Atom-Transfer Radical Cyclization Using Silicon Tethers on Acyclic Precursors

A novel strategy for the stereoselective construction of all-carbon quaternary centers on acyclic molecules using a two-step tandem process is reported. The first step involves an intramolecular and stereoselective atom transfer radical cyclization reaction from an allyl or vinyl subunit attached on a silyloxy, serving as a tether, to a tertiary radical α to an ester. A subsequent mild acidic elimination leads stereoselectively to a quaternary center bearing an allyl or a vinyl in high yield.