Enantioselective Cyanation/Brook Rearrangement/C-Acylation Reactions of Acylsilanes Catalyzed by Chiral Metal Alkoxides
摘要:
New catalytic enantioselective cyanation/1,2-Brook rearrangement/C-acylation reactions of acylsilanes (4) with cyanoformate esters (7) are described. The products of the reaction are fully substituted malonic acid derivatives (8). Catalysts for this transformation were discovered via a directed candidate screen of 96 metal-ligand complexes. Optimization of a (salen)aluminum complex revealed significant remote electronic effects and concentration effects. The scope of the reaction was investigated by using a number of aryl acylsilanes and cyanoformate esters. Chemoselective reduction of the reaction products (8) afforded new enantioenriched alpha-hydroxy-alpha-aryl-beta-amino acid derivatives (32-34) and beta-lactams (35 and 36). This reaction provides a simple method for the construction of new nitrogen-containing enantioenriched chiral building blocks.
Mechanism and Scope of the Cyanide-Catalyzed Cross Silyl Benzoin Reaction
作者:Xin Linghu、Cory C. Bausch、Jeffrey S. Johnson
DOI:10.1021/ja044086y
日期:2005.2.1
the cross silyl benzoinreaction. A study of the influence of water on the KCN-catalyzed cross silyl benzoin addition revealed more practical reaction conditions using unpurified solvent under ambient conditions. A sequential silyl benzoin addition/cyanation/O-acylation reaction that resulted in two new C-C bonds was achieved in excellent yield. The mechanism of cross silyl benzoin addition is proposed
在这项工作中,描述了由金属氰化物催化的酰基硅烷 (1) 和醛 (2) 之间的交叉甲硅烷基安息香加成反应。不对称的芳基、杂芳基和烷基取代的安息香加合物可以以中等至极好的收率生成,使用氰化钾和相转移催化剂进行完全区域控制。从过渡金属氰化物配合物的筛选中,三氰化镧被确定为用于交叉甲硅烷基安息香反应的改进的第二代催化剂。水对 KCN 催化的交叉甲硅烷基安息香加成的影响的研究揭示了在环境条件下使用未纯化溶剂的更实用的反应条件。产生两个新的 CC 键的顺序甲硅烷基安息香加成/氰化/O-酰化反应以优异的产率实现。详细提出了交叉甲硅烷基安息香加成的机制,并得到了交叉研究和许多旨在确定关键步骤可逆性的明确实验的支持。更亲电子的醛组分的氰化不会产生生产性化学反应。碳-碳键的形成被证明是反应中最后的不可逆步骤。
Enantioselective Synthesis of Chiral 3-Substituted-3-silylpropionic Esters <i>via</i>
Rhodium/Bisphosphine-Thiourea-Catalyzed Asymmetric Hydrogenation
We have successfully developed the asymmetric hydrogenation of β‐silyl‐α,β‐unsaturatedesters to prepare chiral 3‐substituted‐3‐silylpropionic esterproducts catalyzed by rhodium/bisphosphine‐thiourea (ZhaoPhos) with excellent results (up to 97% yield, >99% ee, 1500 TON). Moreover, our hydrogenation products can be efficiently converted to other important organic molecules, such as chiral ethyl (R
Metallophosphites as Umpolung Catalysts: The Enantioselective Cross Silyl Benzoin Reaction
作者:Xin Linghu、Justin R. Potnick、Jeffrey S. Johnson
DOI:10.1021/ja0496468
日期:2004.3.1
metallophosphites as catalysts. As a result, nonenzymatic asymmetric cross silyl benzoin reactions have been achieved, giving optically active silyl ether-protected benzoin adducts. The reaction is general with respect to aryl, alkyl, and heterocyclic substrates with good to excellent yields and good to excellent enantioselectivities.
Asymmetric Synthesis of <i>cis</i>-2-Aminocyclopropanols by Intramolecular Mannich Addition of Silyloxy Benzyl Carbanions
作者:Bo Liu、Chong-Dao Lu
DOI:10.1021/jo200585r
日期:2011.5.20
highly diastereoselective method for the preparation of protected cis-2-aminocyclopropanols from N-tert-butanesulfinyl ketimines and various aryl acylsilanes is described. A tandem process for carbon–carbon bond formation via nucleophilic addition to acylsilanes, Brook rearrangement, and intramolecular Mannich reaction has been developed.
A highly stereoselective approach to tetrasubstituted (E)-β-hydroxy silyl enol ethers by addition of aryl-substituted oxiranyl anions to acylsilanes
作者:Cheng Wang、Zubao Gan、Ji Lu、Xia Wu、Zhenlei Song
DOI:10.1016/j.tetlet.2011.02.108
日期:2011.5
A highlystereoselective approach to tetrasubstituted (E)-β-hydroxy silyl enol ethers is described. The reaction proceeds via a sequential addition/[1,2]-Brook rearrangement/epoxide-opening process of aryl-substituted oxiranyl anions with acylsilanes.