A Silicon Tether Approach for Diastereocontrol in Radical Addition to Chiral Hydrazones
作者:Gregory K. Friestad
DOI:10.1021/ol991059h
日期:1999.11.1
A radical carbon-carbon bond construction approach to chiral a branched amines is presented. Stereocontrolled radical addition to chiral hydrazones can be achieved by virtue of conformational constraints imposed during cyclizations using a temporary silicon connection. Oxidative removal of the tether completes the hydroxymethylation process to afford anti-2-hydrazino-1,3-diols 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.
A Silicon Tether Approach for Addition of Functionalized Radicals to Chiral α-Hydroxyhydrazones: Diastereoselective Additions of Hydroxymethyl and Vinyl Synthons
作者:Gregory K. Friestad、Sara E. Massari
DOI:10.1021/jo035405r
日期:2004.2.1
Stereocontrolled additions of hydroxymethyl and vinyl groups to chiral α-hydroxyhydrazones can be achieved by radical cyclizations using bromomethyl or vinyl radical precursors tethered via a temporarysiliconconnection. Tin-mediated 5-exo radical cyclization of α-hydroxyhydrazones using a silicon-tethered bromomethyl group, followed by oxidative removal of the tether, provides anti-2-hydrazino 1