A silicon tether approach for diastereocontrol in radical addition to chiral hydrazones

A radical carbon-carbon bond construction approach to chiral a branched ami nes is presented. Stereocontrolled radical addition to chiral hydrazones ca n be achieved by virtue of conformational constraints imposed during cycliz ations using a temporary silicon connection. Oxidative removal of the tethe r completes the hydroxymethylation process to afford anti-2-hydrazino-1,3-d iols in good yield. The 1,2-induction increases with increasing A values of the appended groups, consistent with prediction by the Beckwith-Houk model for stereocontrol in 5-hexenyl radical cyclizations.