soluble in halogenated organic solvents such as
methylene chloride, chloroform, carbon tetrachloride; sparingly
soluble in hydrocarbon and ethereal solvents.
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.
Lewis Base Catalyzed, Enantioselective Aldol Addition of Methyl Trichlorosilyl Ketene Acetal to Ketones
作者:Scott E. Denmark、Yu Fan、Martin D. Eastgate
DOI:10.1021/jo0506276
日期:2005.6.1
addition of an acetate enolate equivalent to ketones is described. Methyl trichlorosilyl ketene acetal reacts with a wide range of ketones in the presence of pyridine N-oxide to afford the aldol addition products in excellent yields. Chiral 2,2‘-pyridyl bis-N-oxides bearing various substituents at the 3,3‘- and 6,6‘-positions also provide excellent yields of the aldolproducts with variable enantioselectivities
Catalytic, Enantioselective Aldol Additions to Ketones
作者:Scott E. Denmark、Yu Fan
DOI:10.1021/ja025670e
日期:2002.4.1
(possessing both axial and central chiral elements) the aldol addition takes place again in excellent yield and with good stereoselectivity. The enantioselectivities of the additions are highly variable (7-86% ee) and are strongly dependent on the structure of the ketone acceptor. Aromatic methylketones gave the highest selectivity, whereas olefinic ketones were the least selective.
已经证明了三氯甲硅烷基乙烯酮缩醛对酮的催化、对映选择性加成。在催化量的吡啶 N-氧化物存在下,乙酸甲酯的三氯甲硅烷基烯醇化物与多种酮(芳香族、烯烃、炔属、脂肪族)发生快速和高产率的羟醛加成反应。此外,在催化量(10 mol%)的手性双吡啶双 N 氧化物(具有轴性和中心手性元素)存在下,醛醇加成再次以优异的产率和良好的立体选择性发生。添加物的对映选择性变化很大(7-86% ee)并且强烈依赖于酮受体的结构。芳族甲基酮的选择性最高,而烯酮的选择性最低。
Synthesis of new bipyridine N,N′-dioxides and their application in asymmetric allylation of benzaldehyde and aldol addition to acetophenone
AbstractTwo methods for the synthesis of newaxiallychiral bipyridine N,N′-dioxides based on catalytic [2+2+2] cyclotrimerization of diynes with nitriles were developed. The N,N′-dioxides were used as catalysts in enantioselectiveallylation of benzaldehyde with allyltrichlorosilane and aldol reaction of trichlorosilyl ketene acetal of methyl acetate with acetophenone. Graphical abstract
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 =C(OMe)OSiClR2 (1e,f) 与苯甲醛的反应。
The synthesis and the rearrangement of O-silyl-O-alkyl keteneacetals into esters of silylacetic acid
1.The conditions of dual reactivity of the esters of α-metalated carboxylic acids with the halides of some organosilicon compounds were examined.2.The rearrangement of O-silyl-O-alkylketeneacetals into esters of silylaceticacid is reported.