A highly chemoselective conjugateaddition of alcohols in the presence of amines is described. The cooperative nature of the catalyst enabled chemoselective activation of alcohols over amines, allowing the conjugateaddition to soft Lewis basic α,β‐unsaturated nitriles. Divergent transformation of the nitrile functionality highlights the utility of the present catalysis.
A Metal-Ligand Cooperative Pathway for Intermolecular Oxa-Michael Additions to Unsaturated Nitriles
作者:Sébastien Perdriau、Douwe S. Zijlstra、Hero J. Heeres、Johannes G. de Vries、Edwin Otten
DOI:10.1002/anie.201412110
日期:2015.3.27
activation of the nitrile through metal–ligand cooperativity is a keystep. The nitrile‐derived Ru‐N moiety is sufficiently Brønsted basic to activate the alcohol and initiate conjugateaddition of the alkoxide to the α,β‐unsaturated fragment. This reaction proceeds in a concerted manner and involves a six‐membered transition state. These features allow the reaction to proceed at ambient temperature in the
Ruthenium Complexes with PNN Pincer Ligands Based on (Chiral) Pyrrolidines: Synthesis, Structure, and Dynamic Stereochemistry
作者:Johan Bootsma、Beibei Guo、Johannes G. de Vries、Edwin Otten
DOI:10.1021/acs.organomet.9b00765
日期:2020.2.24
Spectroscopic, crystallographic, and computational studies demonstrate that the C-centered chirality from the chiral pyrrolidine group exerts a small but non-negligible influence on the preferred stereochemistry at Ru (and N in the case of (R)-2-methylpyrrolidine) that is reflected in the equilibrium distribution of diastereomers of these Ru complexes in solution. Our data show that the N- and Ru-based
我们报告了基于N侧臂的非手性(吡咯烷)和手性((R,R)-2,5-二甲基吡咯烷和(R)-2-甲基吡咯烷)取代基的基于二甲基吡啶的PNN型金属钳配合物的合成钳配体。以具有芳香族吡啶配体主链的六配位饱和Ru钳(PNN)Ru(H)(CO)(Cl)为起始原料,用强碱(KO t Bu)处理生成相应的脱芳族钳分子(PNN')Ru(H)(CO)。光谱,晶体学和计算研究表明,手性吡咯烷基团的C中心手性对Ru(和N(在(R)-2-甲基吡咯烷)反映在溶液中这些Ru络合物的非对映异构体的平衡分布中。我们的数据显示,这类化合物中基于N和Ru的立体异构中心在立体化学上不稳定,并且讨论了差向异构化的机制。提出通过脱芳构化的Ru(0)中间体发生Ru芳构化复合物中Ru中心的转化,在该中间体中Ru结合的氢化物转移至配体。支持这一点的是通过与CO反应获得的密切相关的Ru(0)物种的光谱表征。在对映选择性oxa-Michael
Nitrile Biotransformations for the Synthesis of Highly Enantioenriched β-Hydroxy and β-Amino Acid and Amide Derivatives: A General and Simple but Powerful and Efficient Benzyl Protection Strategy To Increase Enantioselectivity of the Amidase
作者:Da-You Ma、De-Xian Wang、Jie Pan、Zhi-Tang Huang、Mei-Xiang Wang
DOI:10.1021/jo800074k
日期:2008.6.1
Biotransformations of a number of racemic beta-hydroxy and beta-amino nitrile derivatives were studied using Rhodococcus erythropolis AJ270, the nitrile hydratase and amidase-containing microbial whole cell catalyst, under very mild conditions. The overall enantioselectivity of nitrile biotransformations was governed predominantly by the amidase whose enantioselectivity was switched on remarkably by an O- and a N-benzyl protection group of the Substrates. While biotransformations of beta-hydroxy and beta-amino alkanenitriles gave low yields of amide and acid products of very low enantiomeric purity, introduction of a simple benzyl protection group on the beta-hydroxy and beta-amino of nitrile substrates led to the formation of highly enantioenriched beta-benzyloxy and beta-benzylamino amides and acids in almost quantitative yield. The easy protection and deprotection operations, high chemical yield, and excellent enantioselectivity render the nitrile biotransformation a useful protocol in the synthesis of enantiopure beta-hydroxy and beta-amino acids.
Dramatic Enhancement of Enantioselectivity of Biotransformations of β-Hydroxy Nitriles Using a Simple <i>O</i>-Benzyl Protection/Docking Group
作者:Da-You Ma、Qi-Yu Zheng、De-Xian Wang、Mei-Xiang Wang
DOI:10.1021/ol0610688
日期:2006.7.1
Catalyzed by the Rhodococcus erythropolis AJ270 whole cell catalyst, the O-benzylated beta-hydroxy alkanenitriles underwent remarkably high enantioselective biotransformations, whereas the biotransformations of free beta-hydroxy alkanenitriles gave very low enantioselectivity. The easy manipulations of O-protection and O-deprotection, excellent chemical and enantiomeric yields of biotransformations, along with the scalability render this enzymatic transformation attractive and practical for the synthesis of highly enantiopure beta-hydroxy alkanoic acids and their amide derivatives.