Asymmetric copper-catalyzed allylic alkylation between allyl bromides and alkyl Grignard reagents using a P-chiral monophosphorus ligand is described. A range of terminal olefins bearing tertiary or quaternary carbon centers were formed in good branched/linear selectivities and excellent enantioselectivities at copper loadings as low as 0.5 mol %.
An efficient and practical protocol for the enantioselective cobalt‐catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2 bar) pressure has been developed. As precatalysts, stable [L2CoCl2] complexes are employed that are activated in situ with Et2AlCl. A modular chiral TADDOL‐derived phosphine–phosphite ligand was identified that allows the conversion of a broad spectrum of substrates
Bidentate Hydroxyalkyl NHC Ligands for the Copper-Catalyzed Asymmetric Allylic Substitution of Allyl Phosphates with Grignard Reagents
作者:Magaly Magrez、Yann Le Guen、Olivier Baslé、Christophe Crévisy、Marc Mauduit
DOI:10.1002/chem.201203969
日期:2013.1.21
Demonstrating their potential: Bidentate alkoxy NHC ligands have been used in the copper‐catalyzed asymmetricallylic alkylation of allylphosphates with Grignard reagents (see scheme). The method provides access to tertiary and quaternary chiral centers with high regio‐ and enantioselectivity. The system is also applied to the synthesis of chiral E,E‐dienes, a key structural motif prevalent in natural
Improvements and Applications of the Transition Metal-Free Asymmetric Allylic Alkylation using Grignard Reagents and Magnesium Alanates
作者:David Grassi、Alexandre Alexakis
DOI:10.1002/adsc.201500495
日期:2015.10.12
Two new N-heterocyclic carbene (NHC) ligands have been synthesized and employed in the transition metal-free asymmetric allylic alkylation (AAA) mediated by Grignardreagents and magnesium alanates. The employment of these ligands showed high yields and improved regio- and enantioselectivity in the formation of tertiary and quaternary stereocenters. Moreover, the low catalyst loading (up to 0.3 mol%)
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