1174909-09-1Relevant articles and documents
γ-Silylated α,ss-unsaturated amides - Preparation by [1,5]-sigmatropic rearrangement and use as masked dienolate equivalents in carbonyl condensations
Green, James R.,Alo, Babajide I.,Majewski, Marek,Snieckus, Victor
experimental part, p. 745 - 759 (2009/12/04)
The reaction of lithium dienolates derived from N,N-dialkylsenecioamides (1a-1c) with triorganosilyl electrophiles occurs initially at the oxygen atom predominantly, and is followed by an O → C silicon migration to afford the γ-silylated senecioamides (4a-4h). The γ-silylated senecioamide Z-4a undergoes fluoride-ion-mediated condensations with aromatic aldehydes to give kinetic α-(6) and thermodynamic γ-(5) condensation product patterns comparable to lithium dienolates. The TiCl4-mediated reactions with aldehydes gives a-products (6) in a highly syn-selective manner. Possible transitionstate models for the syn-selective condensations are discussed and a chair-like transition state featuring bidentate coordination to titanium (11) is proposed.
