作者:Scott E. Denmark、Robert A. Stavenger、Stephen B. D. Winter、Ken-Tsung Wong、Paul A. Barsanti
DOI:10.1021/jo981740h
日期:1998.12.1
A variety of chlorosilyl enolates has been prepared starting from esters, thiol esters, acylsilanes, and ketones. Two general methods are involved, direct enolsilylation with trichlorosilyl triflate and diisopropylethylamine, and a number of methods based on electrophilic substitution of either C- or O-silyl or stannyl carbonyl compounds. The most useful method is a Hg(OAc)(2)-catalyzed trans-silylation from trimethylsilyl to trichlorosilyl enol ethers, providing a wide range of ketone enolates in good to high yield.
The Chemistry of Chlorosilyl Enolates 3.: Variation of the Silyl Group and the Effect on Rate and Enantiomeric Excess of Acetate Aldol Additions
作者:Scott Denmark、Stephen Winter
DOI:10.1055/s-1997-1543
日期:1997.9
The rates of reaction of the silyl ketene acetals CH2=C(OMe)OSiCl2R (1a-d) with benzaldehyde and pivalaldehyde have been determined and follow the order R = H ~ Cl > Ph > Me. These reactions are promoted by catalytic amounts of a chiral phosphoramide; enantioselectivities of the products obtained show a high sensitivity towards variation of the silyl group. The reactions of the dialkyl substituted chlorosilyl enolates CH2=C(OMe)OsiClR2 (1e,f) with benzaldehyde are not promoted by HMPA.
甲硅烷基烯酮缩醛 CH2=C(OMe)OSiCl2R (1a-d) 与苯甲醛和新戊醛的反应速率已确定,并遵循 R = H ~ Cl > Ph > Me 的顺序。这些反应由催化量的手性磷酰胺促进;所得产物的对映选择性显示出对甲硅烷基变化的高敏感性。 HMPA 不促进二烷基取代的氯甲硅烷基烯醇化物 CH2=C(OMe)OsiClR2 (1e,f) 与苯甲醛的反应。