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。
Photoreaction of Acetoacetate
作者:Masaru Tada、Tadayoshi Kokubo、Tadashi Sato
DOI:10.1246/bcsj.43.2162
日期:1970.7
Methyl acetoacetate was irradiated in the presence of cyclohexene to afford methyl 3-cyclohexyl-3-hydroxybutyrate (VIII), methyl 3-cyclohexenyl-3-hydroxybutyrate (IX), two oxetanes (Xa and Xb), and cyclohexene dimers. In contrast to acetylacetone, acetoacetate behaves as a saturated ketone rather than as an α,β-unsaturated ester on photoreaction. We concluded that the n-π* excitation of the enol-form of β-dicarbonyl compound is responsible for photo-cycloaddition, and no effective n–π* excitation is accesisble on irradiaron of the enol-form of acetoacetate, since the enol form of acetoacetate has its n–π* and π-π* absorptions in the same region.