Improved Conditions for the Proline-Catalyzed Aldol Reaction of Acetone with Aliphatic Aldehydes
作者:Benjamin List、Alberto Martínez、Kristina Zumbansen、Arno Döhring、Manuel van Gemmeren
DOI:10.1055/s-0033-1340919
日期:——
The proline-catalyzed asymmetric aldol reaction between aliphatic aldehydes and acetone has, to date, remained underdeveloped. Challenges in controlling this reaction include avoiding undesired side reactions such as aldol condensation and self-aldolization. In recent years we have developed optimized conditions, which enable high yields and good to excellent enantioselectivities, and which are presented
Proline-Catalyzed Asymmetric Aldol Reactions between Ketones and α-Unsubstituted Aldehydes
作者:Benjamin List、Peter Pojarliev、Chris Castello
DOI:10.1021/ol006976y
日期:2001.2.1
[reaction: see text] With this communication we extend the methodology of proline-catalyzed direct asymmetric aldol reactions to include alpha-unsubstituted aldehydes as acceptors. This important aldehyde class gives the corresponding aldols in 22-77% yield and up to 95% ee when the reactions are performed in pure acetone or in ketone/chloroform mixtures. On the basis of these results we have developed
Direct Asymmetric Aldol Reactions of Acetone Using Bimetallic Zinc Catalysts
作者:Barry M. Trost、Elliad R. Silcoff、Hisanaka Ito
DOI:10.1021/ol0161211
日期:2001.8.9
[reaction: see text] The enantioselective aldolreaction using a novel binuclear zinccatalyst of acetone with several aldehydes gave products in good yields (62-89%) with a high level of enantioselectivity (ee = 76-92%).
as competing nucleophiles. D6 turned out to be the key residue that enabled activity with non‐hydroxylated nucleophiles. Altogether 25 single‐ and double‐site variants (D6X and D6X/T26X) were discovered that show useful synthetic activity and a varying preference for ketone or aldehyde as the aldol nucleophiles. Remarkably, all of the novel variants had completely lost their native activity for cleavage
Enantioselective Synthesis of Cyclic Enol Ethers and All-Carbon Quaternary Stereogenic Centers Through Catalytic Asymmetric Ring-Closing Metathesis
作者:Ai-Lan Lee、Steven J. Malcolmson、Alessandra Puglisi、Richard R. Schrock、Amir H. Hoveyda
DOI:10.1021/ja058428r
日期:2006.4.1
enriched form. Thus, Mo-catalyzed enantioselective transformations allow access to various five- and six-membered cyclic enol ethers in up to 94% ee fromreadilyavailable achiral startingmaterials. The first examples of catalytic ARCM that lead to the formation of all-carbon quaternary stereogenic centers are also disclosed. Mechanistic models that offer a plausible rationale for the identity of major
报道了烯醇醚催化不对称闭环复分解 (ARCM) 反应的第一个例子。为了确定最有效的催化剂,筛选了各种手性 Mo 和 Ru 基催化剂。尽管手性 Ru 催化剂(那些不带有膦配体的催化剂)在某些情况下会促进 ARCM,但这种转化以 <10% ee 进行。相比之下,基于钼的亚烷基产生高效的 ARCM,并以光学富集的形式提供所需的产品。因此,Mo 催化的对映选择性转化允许从容易获得的非手性起始材料中获得高达 94% ee 的各种五元和六元环烯醇醚。还公开了导致形成全碳四元立体中心的催化ARCM的第一个例子。提供了为主要对映异构体的身份以及观察到的对映选择性水平提供合理依据的机械模型。代表性实例表明,ARCM 产物的烯醇醚部分和未反应的烯烃可以以优异的位点选择性 (>98%) 区分。