Catalytic Enantioselective Addition of MeMgBr and Other Grignard Reagents to Aldehydes
作者:Emilio Fernández-Mateos、Beatriz Maciá、Diego J. Ramón、Miguel Yus
DOI:10.1002/ejoc.201101283
日期:2011.12
Herein, we report an efficient catalyst for the challenging enantioselectiveaddition of MeMgBr to aldehydes. Unprecedented yields and enantioselectivities are achieved in the reaction with a broad range of aldehydes. Moreover, a variety of Grignard reagents can be also added to aromatic and aliphatic aldehydes in good yields and enantioselectivities in a simple one-pot procedure under mild conditions.
an efficient catalytic system for the enantioselectiveaddition of alkyl Grignard reagents to a broad range of aliphatic aldehydes with good yields and enantioselectivities. Remarkably, the challenging methylmagnesium bromide (MeMgBr) can also be added to a variety of aliphatic aldehydes, providing versatile chiral methyl carbinol units with unprecedented yields and enantioselectivities in a simple
Nucleophilic cleavages of acetals using organotitanium reagents. A new synthesis of chiral alcohols
作者:Atsunori Mori、Keiji Maruoka、Hisashi Yamamoto
DOI:10.1016/s0040-4039(01)81455-6
日期:1984.1
A highlychemo- and stereoselective cleavage of acetals derived from (−)-(2R,4R)-2,4-pentanediol with organotitanium reagents has been demonstrated. The reaction proceeds under mild conditions in excellent yield and high chemoselectivity to give, after removal of auxiliary, the chiral alcohols of high enantiopurities. In addition, complexation of chiral acetals and TiCl4 followed by treatment with
Enantioselective preparation of sec. Alcohols from aldehydes and dialkyl zinc compounds, generated in situ from Grignard reagents, using substoichiometric amounts of TADDOL-titanates
作者:Joanna Linda von dem Bussche-Hünnefeld、Dieter Seebach
DOI:10.1016/0040-4020(92)80023-9
日期:1992.7
the Schlenk trick (precipitation of MgX2 from ethereal solutions by the addition of 1,4-dioxane) mixtures of a Grignard reagent RMgX (X = Cl, Br, I) and 0.5 equiv. ZnCl2 in Et2O can be converted to zinc alkyls R2Zn which in turn are added with enantio-selectivities of up to 99 : 1 to aliphatic and aromatic aldehydes in the presence of Ti(OCHMe2)4 and a chiral titanate derived from an α,α,α′,α′-tetraaryl-1
Kinetic resolution of racemic allylic alcohols <i>via</i> iridium-catalyzed asymmetric hydrogenation: scope, synthetic applications and insight into the origin of selectivity
作者:Haibo Wu、Cristiana Margarita、Jira Jongcharoenkamol、Mark D. Nolan、Thishana Singh、Pher G. Andersson
DOI:10.1039/d0sc05276k
日期:——
Asymmetric hydrogenation is one of the most commonly used tools in organic synthesis, whereas, kineticresolution via asymmetric hydrogenation is less developed. Herein, we describe the first iridium catalyzed kineticresolution of a wide range of trisubstituted secondary and tertiary allylic alcohols. Large selectivity factors were observed in most cases (s up to 211), providing the unreacted starting
不对称氢化是有机合成中最常用的工具之一,而通过不对称氢化进行动力学拆分的开发较少。在此,我们描述了各种三取代仲和叔烯丙醇的第一次铱催化动力学拆分。在大多数情况下观察到较大的选择性因子(高达211),从而以良好的收率和高水平的对映体纯度(ee 高达 >99%)提供未反应的起始材料。该方法的实用性在一些生物活性天然产物的对映选择性正式合成中得到了强调,包括 pumiliotoxin A、inthomycin A 和 B。提出了 DFT 研究和关于选择性起源的选择性模型。