通过简便的路线,以良好的产率合成了一系列基于酰腙的N,N-螯合半夹心铱配合物。所制备的空气稳定铱配合物在温和的反应条件下催化一系列芳香族和脂肪族伯醇脱氢生成相应的羧酸。在敞口烧瓶条件下以高产率获得了羧酸,具有广泛的底物和对敏感官能团的良好耐受性。这种半夹心铱催化剂体系表现出较高的催化活性和稳定性,在催化剂负载量低至0.05 mol%的情况下即可实现316.7 h –1的高TOF。此外,这种可持续催化剂可以重复使用至少五次而不会明显失去活性,凸显了其在工业中的潜在应用。通过单晶X射线分析证实了铱配合物1的分子结构。
采用基于铜 (I)/NHC 配合物和胍有机催化剂的双功能催化剂,促进了以 H 2作为末端还原剂的催化酯还原成醇。这里采用的方法能够通过氢键同时活化酯,并从 H 2形成亲核的氢化铜 (I) ,从而导致氢化物催化转移到酯。由胍亚基介导的质子穿梭进一步促进了还原步骤。这种酯还原的双功能方法首次将通常认为的“软”氢化铜 (I) 的反应性转变为以前不反应的“硬”酯亲电子试剂,并为用催化剂和 H 2替代化学计量还原剂铺平了道路.
Electrocatalytic Hydrocarbon Hydroxylation by Ethylbenzene Dehydrogenase from Aromatoleum aromaticum
摘要:
We report the electrocatalytic activity of ethylbenzene dehydrogenase (EBDH) from the beta-proteobacterium Aromatoleum aromaticum. EBDH is a complex 155 kDa heterotrimeric molybdenum/ironsulfur/heme protein which catalyzes the enantioselective hydroxylation of nonactivated ethylbenzene to (S)-1-phenylethanol without molecular oxygen as cosubstrate. Furthermore, it oxidizes a wide range of other alkyl-substituted aromatic and heterocyclic compounds to their secondary alcohols. Hydroxymethylferrocenium (FM) is used as an artificial electron acceptor for EBDH in an electrochemically driven catalytic system. Electrocatalytic activity of EBDH is demonstrated with both its native substrate ethylbenzene and the related substrate p-ethylphenol. The catalytic system has been modeled by electrochemical simulation across a range of sweep rates and concentrations of each substrate, which provides new insights into the kinetics of the EBDH catalytic mechanism.
Catalytic access to ferrocenyl phosphines bearing both planar and central chirality – A kinetic resolution approach via catalytic asymmetric P(III)–C bond formation
作者:Abdul Sadeer、Tadayuki Kojima、Jia Sheng Ng、Kennard Gan、Renta Jonathan Chew、Yongxin Li、Sumod A. Pullarkat
DOI:10.1016/j.tet.2020.131259
日期:2020.6
A series of enantioenriched ferrocenyl monophosphines imbued with both central and planarchirality were obtained catalytically (80–99% ee) via the kinetic resolution of 1,2-disubstituted planarchiral ferrocenyl enone racemates. The synthetic approach utilized a chiral palladacycle to facilitate the asymmetric hydrophosphination (AHP) as a means to achieve high stereoselectivity. The enantioenriched
Hydrosilylation of aldehydes and ketones catalysed by nickel acetate and tricyclohexylphosphine as the catalytic system was demonstrated using polymethylhydrosiloxane as a cheap reducing reagent.
The development of catalysts based on earth abundant metals in place of noble metals is becoming a central topic of catalysis. We herein report a cobalt/tetraphosphine complex catalyzed homogeneous hydrogenation of polar unsaturated compounds using an air- and moisture-stable and scalable precatalyst. By activation with potassium hydroxide, this cobalt system shows both high efficiency (up to 24000
Reaction condition controlled nickel(<scp>ii</scp>)-catalyzed C–C cross-coupling of alcohols
作者:Meng-Juan Zhang、Hong-Xi Li、David J. Young、Hai-Yan Li、Jian-Ping Lang
DOI:10.1039/c9ob00418a
日期:——
methodology employing a Ni(II) 4,6-dimethylpyrimidine-2-thiolate cluster catalyst under different reaction conditions. This catalyst could tolerate a wide range of substrates and exhibited a high activity for the annulation reaction of secondary alcohols with 2-aminobenzyl alcohols to yield quinolines. This work is an example of precise chemoselectivity control by careful choice of reaction conditions.