Lewis acid-catalyzed enantioselective vinylsilane additions

ORGN 684

Yimon Aye, yimonaye@fas.harvard.edu, Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 and DA. Evans, fabio@chemistry.harvard.edu, Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138.

An enantioselective and stereospecific scandium(pybox)-catalyzed vinylsilane addition to glyoxamide has been developed. This represents the first chiral Lewis acid-catalyzed alkenylation with vinylsilanes as an approach to enantiopure allylic alcohols. Norephedrine-pybox, conveniently synthesized in a two-step sequence from a commercially available and inexpensive amino alcohol norephedrine, is employed as a chiral ligand. Both aliphatic and aromatic vinylsilanes bearing a range of substitution patterns are effective coupling partners. Twelve examples have been demonstrated so far, all with excellent enantioselectivites (>97% ee) and in good yields (>59-99%). All reactions utilize non-toxic, easily-prepared and air- and moisture-stable trimethyl-vinylsilanes and are efficient at room temperature. Reactions proceed with full retention in olefin geometry. All products are highly crystalline solids, ideally suited for pharmaceutical process chemistry.