A new, practical route to enoxysilanes is described from simple enolizable aldehydes or ketones, using the trimethylchlorosilane-sodium iodide—tertiary amine reagent in acetonitrile. From certain aldehydes, an onium intermediate has been isolated. A conformational study of this onium intermediate and a thermal unimolecular syn-elimination process may explain the stereoselectivity of the reaction. Such
Kinetic Enolate Formation by Lithium Arylamide: Effects of Basicity on Selectivity
作者:Linfeng Xie、Keith Vanlandeghem、Kurt M. Isenberger、Carolyn Bernier
DOI:10.1021/jo0263465
日期:2003.1.1
Five ketones R1COCH2R2 (1a-e) were enolized in tetrahydrofuran solvent employing lithium arylamides with different electron-withdrawing and -donating substituents on the phenyl ring (4a-e). Enolate selectivity is unaffected by a moderate electron-releasing or -withdrawing group, but significantly enhanced by strong electron-withdrawing substituents to yield predominantly Z-enolate. Outstanding selectivity
Sur l'obtention hautement regio-et stereoselective d'enoxysilanes par action du bis(trimethylsilyl) acetamide en milieu hmpt sur les derives carbonyles enolisables
作者:James Dedier、Pierre Gerval、Emile Frainnet
DOI:10.1016/s0022-328x(00)85896-9
日期:1980.2
The authors describe a new and general method for the preparation of enoxysilanes by silylation of enolizable aldehydes and ketones by use of bis(trimethylsilyl) acetamide in HMPT, in the presence of very small quantities of sodium metal(or another basic agent) as catalyst. This method was found to proceed rapidly, with good yields, and is highly regio-and stereo-selective (giving the Z isomer, orientation
Potassium or ammonium carboxylates catalyzed Mannich-type reaction between trimethylsilyl enolates and aldimines proceeded smoothly to afford the corresponding β-amino carbonyl compounds in good to high yields with high anti selectivity.
The cross-aldol reaction between a ketone and an aldehyde proceeded smoothly with threo diastereoselection favorably mediated by ytterbium trifluoromethanesulfonate and tertiary amine in diethyl ether or in dichloromethane. A ytterbium enolate was trapped with chlorotrimethylsilane to afford a silyl enol ether.