Stereoselective Synthesis of (E)-Enol Borinates via Borylation of Lithum Enolates
Truong, Tram Tu 1992-
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Aldol reactions of enol borinates constitute one the most powerful and reliable methods for asymmetric synthesis. Crucial to this success is the stereoselective preparation of enol borinates and ‘soft enolization’ is by far the most popular method; however, limitations in substrate scope have been reported, particularly with sterically hindered ketones and those incompatible with the Lewis acidic reagents. Borylation of lithium enolates was found to be a general and efficient approach to enol borinates that can overcome many of the above limitations. Under appropriate conditions, the (E)-enol borinate is produced with high diastereoselectivity regardless of the starting geometry of the precursor Li enolate. The mechanism of the underlying isomerization process is unusual. The method has been implemented successfully across a range of ketone substrates and is complementary to ‘soft enolization’ with the advantages that reactivity is dependent on lithium enolate formation and stereoselectivity is independent of the geometry of lithium enolate.
DegreeMaster of Science (M.Sc.)
CommitteeBowles, Richard; Gravel, Michel; Dimmock, Jonathan
Copyright DateDecember 2018