“Super Silyl” Group for Diastereoselective Sequential Reactions: Access to Complex Chiral Architecture in One Pot
摘要:
We have shown that the tris(trimethylsilyl)silyl (TTMSS) silyl enol ether of acetaldehyde undergoes aldehyde cross-aldol reactions with high selectivity and the extremely low catalyst loading (0.05 mol % of HNTf2) allows for one-pot sequential reactions where acidic or basic nucleophiles can be subsequently added. Various ketone-derived silyl enol ethers, Grignard reagents, and dienes succeeded, generating relatively complex molecular architectures in a single step. This represents the first case where, in a single pot, highly acidic conditions followed by very basic conditions were tolerated to give products with high diastereoselectivities and good yields.
The use of the tris(trimethylsilyl)silyl (TTMSS) group in aldehyde-derived silyl enol ethers affords aldehyde cross-aldol products with high yields and allows for unprecedented reactivity. The reaction is catalyzed by 0.05 mol % of HNTf2, and can easily be managed to give beta,delta-bis-, beta,delta,gamma-tris-, and beta,delta,zeta-tris-hydroxy-aldehydes with extremely high selectivity by simple stoichiometric control. High diastereoselectivity is obtained in all cases, and the use of chiral aldehydes affords Felkin products when there are nonchelating substituents, chelation products when there is a chelating sbustituent, and syn products when there is beta-substitution. HNTf2 is proposed to be an initiator, and highly Lewis acidic TTMSSNTf2 is the true catalyst.
Ketone Super Silyl Enol Ethers in Sequential Reactions: Diastereoselective Generation of Tertiary Carbinols in One Pot
作者:Matthew B. Boxer、Matsujiro Akakura、Hisashi Yamamoto
DOI:10.1021/ja7102586
日期:2008.2.6
Ketone super silyl enolethers are shown to be excellent nucleophiles in the Mukaiyama aldol reaction as well as in sequential one-pot diastereoselective reactions. High yields and diastereoselectivities are obtained with a variety of silyl enolether/aldehyde/Grignard combinations. The utility of this reaction is exemplified in a one-pot 4-component reaction generating two secondary and one tertiary
Controlling stereochemistry in polyketide synthesis: 1,3- vs. 1,2-asymmetric induction in methyl ketone aldol additions to β-super siloxy aldehydes
作者:Patrick B. Brady、Brian J. Albert、Matsujiro Akakura、Hisashi Yamamoto
DOI:10.1039/c3sc51183a
日期:——
The aldol addition of methyl ketones to β-siloxy and α-methyl β-siloxy aldehydes is described. Careful control of mechanistically distinct aldol reactions leverages 1,2- and 1,3-asymmetric induction, selectively forming syn and anti aldol adducts with excellent diastereocontrol. Experimental and theoretical investigations have provided insight to the factors governing diastereoselectivity.
Confinement-Controlled, Either <i>syn</i>- or <i>anti</i>-Selective Catalytic Asymmetric Mukaiyama Aldolizations of Propionaldehyde Enolsilanes
作者:Tynchtyk Amatov、Nobuya Tsuji、Rajat Maji、Lucas Schreyer、Hui Zhou、Markus Leutzsch、Benjamin List
DOI:10.1021/jacs.1c07447
日期:2021.9.15
Protected aldols (i.e., true aldols derived from aldehydes) with either syn- or anti- stereochemistry are versatile intermediates in many oligopropionate syntheses. Traditional stereoselectiveapproaches to such aldols typically require several nonstrategic operations. Here we report two highly enantioselective and diastereoselective catalytic Mukaiyama aldol reactions of the TBS- or TES- enolsilanes
具有顺式或反式立体化学的受保护醛醇(即来自醛的真正醛醇)是许多低聚丙酸酯合成中的通用中间体。这种醛醇的传统立体选择性方法通常需要几个非战略性操作。在这里,我们报告了丙醛的 TBS-或 TES-烯醇硅烷与芳香醛的两种高度对映选择性和非对映选择性催化 Mukaiyama 羟醛反应。我们的反应以催化剂控制的方式直接提供有价值的甲硅烷基保护的丙醛醛醇,无论是合成还是反异构体。我们已经确定了一种特权 IDPi 催化剂基序,该基序专为控制这些醛醇化反应而设计,具有出色的选择性。我们展示了 IDPi 催化剂内核中的单原子修饰,用CF 2 H 基团替换 CF 3基团,如何导致醛的对映面分化发生戏剧性的转变。这种显着效果的起源归因于通过 CF 2 H 基团的非常规 C-H 氢键使催化腔变紧。
Remarkable Tris(trimethylsilyl)silyl Group for Diastereoselective [2 + 2] Cyclizations
作者:Matthew B. Boxer、Hisashi Yamamoto
DOI:10.1021/ol0512334
日期:2005.7.1
[reaction: see text] Diastereoselective [2 + 2] cyclizations of aldehyde- and ketone-derived silyl enol ethers with acrylates is described. The use of the tris(trimethylsilyl)silyl group allows for unprecedented reactivity, yields, and selectivity for these cyclizations. The presence of silicon-silicon bonds proved to be important for this transformation, where typical silyl groups (TBS and TIPS) failed
Rapid Total Syntheses Utilizing “Supersilyl” Chemistry
作者:Brian J. Albert、Yousuke Yamaoka、Hisashi Yamamoto
DOI:10.1002/anie.201007210
日期:2011.3.7
In short order: The shortest total syntheses of natural product EBC‐23 (see scheme, PMB=para‐methoxybenzyl, TMS=trimethylsilyl) and a polymethoxy‐1‐alkene to date have been accomplished in just ten total steps each from commercially available chemicals. The syntheses took advantage of highly diastereoselective supersilyl‐directed cascade polyaldol reactions.