Highly Enantioselective Transfer Hydrogenation of Prochiral Ketones Using Ru(II)-Chitosan Catalyst in Aqueous Media
作者:György Szőllősi、Vanessza Judit Kolcsár
DOI:10.1002/cctc.201801602
日期:2019.1.23
Unprecedentedly high enantioselectivities are obtained in the transferhydrogenation of prochiral ketones catalyzed by a Ru complex formed in situ with chitosan chiral ligand. This biocompatible, biodegradable chiral polymer obtained from the natural chitin afforded good, up to 86 % enantioselectivities, in the aqueous‐phase transferhydrogenation of acetophenone derivatives using HCOONa as hydrogen donor. Cyclic
在与壳聚糖手性配体原位形成的Ru络合物催化的前手性酮的转移氢化中,获得了前所未有的高对映选择性。这种从天然几丁质中获得的生物相容性,可生物降解的手性聚合物,在使用HCOONa作为氢供体的苯乙酮衍生物的水相转移氢化中,提供了高达86%的良好对映选择性。环酮的对映选择性更高,超过90%,而在杂环酮的转移氢化中,进一步增加,最高可达97%。手性催化剂前体制备易地通过扫描电子显微镜,FT-中期和-far-IR光谱法检测。原位结构通过1 H NMR光谱和使用各种壳聚糖衍生物研究了形成的催化剂。结果表明,Ru预催化剂是通过氨基将生物聚合物与金属配位而形成的。加入氢供体后,该前体转化为水不溶性钌氢化物络合物。通过以高收率和光学纯度制备二十多种手性醇,验证了所开发方法的实用价值。在单次结晶后,将催化剂用于以克为单位获得光学纯的手性醇。
Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by the TolBINAP/DMAPEN−Ruthenium(II) Complex: A Significant Effect of <i>N</i>-Substituents of Chiral 1,2-Diamine Ligands on Enantioselectivity
mode of enantioface selection was interpreted by using transition state models based on the X-ray structure of the catalyst precursor. The chiral catalyst effected the hydrogenation of alkyl aryl ketones and arylglyoxal dialkyl acetals to afford the chiral alcohol in >99% ee in the best cases. Hydrogenation of racemic benzoin methyl ether with the chiral catalyst through dynamic kinetic resolution gave
Heterogeneous Enantioselective Hydrogenation in a Continuous-flow Fixed-bed Reactor System: Hydrogenation of Activated Ketones and Their Binary Mixtures on Pt–Alumina–Cinchona Alkaloid Catalysts
racemic (Cr) hydrogenations of all three compounds and enantioselectivities (ee) were determined under the same experimental conditions (under 4 MPa H2 pressure, at room temperature using toluene/AcOH 9/1 as solvent).The order of the rates of the enantioselectivehydrogenations of the three substrates studied is MBF > PA > DAP, and the order of their ee values is MBF ~ PA > DAP. The hydrogenation rate and
在 Orito 反应的实验条件下,苯甲酰甲酸甲酯 (MBF)、丙酮醛二甲缩醛 (PA) 和 2,2-二乙氧基苯乙酮 (DAP) 的三种二元混合物在辛可尼丁改性的铂-氧化铝催化剂上的单独加氢和竞争加氢、辛可宁、奎宁和奎尼丁(Pt-CD、Pt-CN、Pt-QN、Pt-QD)首次使用连续流固定床反应器系统进行了研究。所有三种化合物的手性 (Cc) 和外消旋 (Cr) 氢化的转化率和对映选择性 (ee) 在相同的实验条件下(在 4 MPa H2 压力下,在室温下使用甲苯/AcOH 9/1 作为溶剂)确定。研究的三种底物的对映选择性氢化速率的顺序是 MBF > PA > DAP,并且它们的ee值的顺序是MBF~PA>DAP。加氢速率和速率对 ee 的影响取决于所用金鸡纳的结构:MBF 和 PA 的加氢可能产生超过 90% 的 ee 值,但是,在存在 Pt-QN 的情况下,ee 值非常低,尤其Pt-QD
Heterogeneous Enantioselective Hydrogenation of Activated Ketones Catalyzed by Modified Pt‐Catalysts: A Systematic Structure‐Selectivity Study
1–5 and 8, all carrying an sp3 carbon next to the keto group) or toluene (6 and 7, with an sp2 carbon next to the ketone). The presence and nature of the substituent R' at the quinuclidine significantly affected the ee (positive and negative effects). Certain combinations of an aromatic system and an amino function were preferred: For the quinuclidine moiety, quinoline and to a somewhat lesser extent
进行了系统的结构选择性研究,用手性改性的Pt / Al 2 O 3催化剂对活化的酮进行对映选择性加氢。为此,有18种改性剂,它们含有能与Pt表面形成强吸附复合物的扩展的芳族体系,以及合适的具有氨基官能团的手性基团,能够与底物的酮基相互作用(HCd,Qd,HCn,Qn在标准条件下,在AcOH和甲苯中的8种不同的活化酮上制备并测试了半合成衍生物以及合成类似物。发现底物和/或改性剂结构的相对较小的结构变化强烈影响对映选择性,并且对于所有底物都不存在“最佳”改性剂。在组合奎宁环衍生的改性剂与萘或喹啉环,获得对于所有底物的最高EES,无论是在AcOH(基板1 - 5和8中,所有承载SP 3旁边碳酮基)或甲苯(6和7,带有sp 2碳旁边的酮)。奎宁环上取代基R'的存在和性质显着影响ee(正效应和负效应)。优选芳族体系和氨基官能团的某些组合:对于喹核苷部分,喹啉和程度较小的萘是更好的匹配,而对于吡咯烷基
Synthesis of enantiomerically pure α-hydroxyaldehydes from the corresponding α-hydroxycarboxylic acids: novel substrates for Escherichia coli transketolase
作者:Andrew J. Humphrey、Nicholas J. Turner、Raymond McCague、Stephen J. C. Taylor
DOI:10.1039/c39950002475
日期:——
Enantiomerically pure (R)-α-hydroxyaldehydes (>95% ee) are prepared from the corresponding α-hydroxyesters by silyl protection, reduction with diisobutylaluminium hydride, and finally deprotection under acidic conditions; subsequent coupling of these aldehydes with lithium hydroxypyruvate, catalysed by Escherichia coli transketolase, leads to novel optically pure triols.