Stereogenic-at-Metal Zn- and Al-Based N-Heterocyclic Carbene (NHC) Complexes as Bifunctional Catalysts in Cu-Free Enantioselective Allylic Alkylations
作者:Yunmi Lee、Bo Li、Amir H. Hoveyda
DOI:10.1021/ja904654j
日期:2009.8.19
detailed herein demonstrate the ability of chiral bidentate N-heterocyclic carbenes to promote directly-without the need for a Cu salt-site- and enantioselective C-C bond forming reactions. Within this context, catalytic allylic alkylations of various allylic phosphates with dialkylzinc and trialkylaluminum reagents, performed with chiral bidentate imidazoliniumsalts and in the absence of a Cu salt, are
本文详述的研究证明了手性双齿 N-杂环卡宾直接促进的能力 - 无需 Cu 盐位 - 和对映选择性 CC 键形成反应。在此上下文中,描述了使用二烷基锌和三烷基铝试剂在手性双齿咪唑啉盐和不存在 Cu 盐的情况下进行的各种烯丙基磷酸酯的催化烯丙基烷基化。无铜转化提供带有三级或(全碳)四级立体中心的产品,具有特殊的位点 - (>98:<2 S(N)2':S(N)2) 和高对映选择性 [高达 97.5:2.5对映体比率(er)]。分离并充分表征了一种手性锌基 N-杂环卡宾 (NHC) 配合物,该配合物用作对映选择性烯丙基烷基化反应的催化剂。光谱和 X 射线晶体学研究表明,在 Zn 双齿复合物中的磺酸盐基团与 NHC 主链的近端苯基取代基同步(相对于最初预期的反)。对相关 NHC-Al 复合物的调查揭示了类似的结构属性。概述的研究提供了关于无铜烯丙基烷基化反应机制的合理原理,该反应涉及二烷基锌或三烷基
Cu-Catalyzed Asymmetric Allylic Alkylations of Aromatic and Aliphatic Phosphates with Alkylzinc Reagents. An Effective Method for Enantioselective Synthesis of Tertiary and Quaternary Carbons
作者:Monica A. Kacprzynski、Amir H. Hoveyda
DOI:10.1021/ja0478779
日期:2004.9.1
Efficient enantioselective Cu-catalyzed allylicalkylations of aromatic and aliphatic allylic phosphates bearing di- and trisubstituted olefins are disclosed. Enantioselective C-C bond forming reactions are promoted in the presence of 10 mol % readily available chiral amino acid-based ligand (5 steps, 40% overall yield synthesis) and 5 mol % (CuOTf)2 x C6H6. Reactions deliver tertiary and quaternary stereogenic
公开了带有二和三取代烯烃的芳族和脂族烯丙基磷酸酯的有效对映选择性Cu催化的烯丙基烷基化。在 10 mol% 容易获得的手性氨基酸基配体(5 步,40% 总产率合成)和 5 mol% (CuOTf)2 x C6H6 存在下,对映选择性 CC 键形成反应得到促进。反应区域选择性地以 78-96% ee 传递叔和四元立体碳中心。提供了有关配体结构变化对烷基化过程的效率和对映选择性的影响的数据,以及机械工作模型。建议的模型涉及手性 Cu 络合物的双重作用:Cu(I) 中心与烯烃的结合是通过配体羰基之间的两点结合来促进的
Enantioselective Synthesis of Alkyne-Substituted Quaternary Carbon Stereogenic Centers through NHC−Cu-Catalyzed Allylic Substitution Reactions with (<i>i</i>-Bu)<sub>2</sub>(Alkynyl)aluminum Reagents
作者:Jennifer A. Dabrowski、Fang Gao、Amir H. Hoveyda
DOI:10.1021/ja2010829
日期:2011.4.6
A catalyticenantioselective method for the formation of alkyne-substituted all-carbon quaternary stereogenic centers is reported. Additions of alkynylaluminums to alkyl-, aryl-, carboxylic ester-, or silyl-substituted allylic phosphates are promoted by 1.0-5.0 mol % loadings of NHC-Cu complexes derived from air-stable and commercially available CuCl(2)·2H(2)O. The requisite Al-based reagents are prepared
Synthesis of Quaternary Carbon Stereogenic Centers through Enantioselective Cu-Catalyzed Allylic Substitutions with Vinylaluminum Reagents
作者:Fang Gao、Kevin P. McGrath、Yunmi Lee、Amir H. Hoveyda
DOI:10.1021/ja106829k
日期:2010.10.13
efficiently (66-97% yield of isolated products) and in high site (>98% S(N)2')- and enantioselectivity [up to 99:1 enantiomer ratio (er)]. To the best of our knowledge, the present report puts forward the first cases of allylic substitution reactions that result in the generation of all-carbon quaternarystereogeniccentersthrough the addition of a vinyl unit. The aryl- and vinyl-substituted vinylaluminum
公开了催化对映选择性烯丙基取代 (EAS) 反应,其涉及使用烷基或芳基取代的乙烯基铝试剂并提供在其 C-3 位点含有季碳立体中心的 1,4-二烯。CC 键形成转化由 0.5-2.5 mol% 的带有手性双齿 N-杂环卡宾 (NHC) 配合物的磺酸盐促进,有效地提供所需的产物(66-97% 的分离产物产率)和高位点(>98 % S(N)2')- 和对映选择性 [高达 99:1 的对映异构体比 (er)]。据我们所知,本报告提出了烯丙基取代反应的第一个案例,该反应导致通过添加乙烯基单元产生全碳四元立体中心。芳基和乙烯基取代的乙烯基铝试剂,不能通过与二异丁基氢化铝直接反应高效制备,可以通过最近引入的相应末端炔烃与相同廉价金属氢化物的 Ni 催化反应获得。连续的 Ni 催化加氢金属化和 Cu 催化的 CC 键形成反应允许有效和选择性地合成一系列富含对映异构体的 EAS 产品,这些产品无法通过先前公
Bidentate NHC-Based Chiral Ligands for Efficient Cu-Catalyzed Enantioselective Allylic Alkylations: Structure and Activity of an Air-Stable Chiral Cu Complex
作者:Andrew O. Larsen、Wenhao Leu、Christina Nieto Oberhuber、John E. Campbell、Amir H. Hoveyda
DOI:10.1021/ja046245j
日期:2004.9.1
Cu-catalyzed addition of alkylzincreagents to a range of allylic phosphates is promoted efficiently and with high enantioselectivity to afford tertiary as well as quaternarycarbon centers (up to 98% ee). Reactions proceed to completion with 0.5-5 mol % catalyst loading and are best promoted by commercially available CuCl2.2H2O. The X-ray structure of the chiral NHC-Ag(I) complex used in the study
Cu催化的烷基锌试剂向一系列烯丙基磷酸酯的加成得到有效促进,并具有高对映选择性,以提供叔和季碳中心(高达 98% ee)。反应在 0.5-5 mol% 的催化剂负载下进行到完成,最好由市售的 CuCl2.2H2O 促进。还报告了研究中使用的手性 NHC-Ag(I) 配合物以及具有催化活性的 NHC-Cu(II) 配合物的 X 射线结构;两种复合物都是空气稳定的,并且以 >/=95% 的分离产率形成。可在空气中处理的分离出的 Cu 络合物具有催化活性。本报告为使用手性 NHC 配体进行有效的铜催化烯丙基烷基化提供了第一个先例。