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1.
Gerlinde Mehler Pawel Linowski Dr. Javier Carreras Dr. Alessandro Zanardi Dr. Jonathan W. Dube Prof. Dr. Manuel Alcarazo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(43):15320-15327
A straightforward route for the preparation of a set of bis(cyclopropenium)‐substituted phosphines is reported. Due to their dicationic nature, these ligands depict an excellent π‐acceptor character. The effect of the ligand substituent pattern on the catalytic activity of the metal complexes thereof derived is also studied. Whereas sterically demanding biaryl groups directly attached to the phosphorus atom seem to facilitate elementary steps such as the product release from the catalyst, long chain dialkylamino groups on the cyclopropenium units maximize the catalysts solubility and, thus, allow the use of typical apolar solvents such as toluene. Importantly, all new ligands prepared can be easily handled in air. Finally, the impact of the newly prepared dicationic phosphines in hydroarylation reactions is demonstrated. In particular, their use in the synthesis of several naphtho[1,2‐b]furanes and naturally occurring naphthalene derivatives such as Calanquinone C is reported. 相似文献
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Two new binuclear cobalt(II) complexes, [Co2 L1 (μ2‐DPP)]2+ ( 1 ) (H L1 = N, N, N′, N′‐ tetrakis (2‐benzimidazolylmethyl)‐2‐hydroxyl ‐1,3‐diaminopropane; DPP = diphenylphosphinate) and [Co2 L2 (μ2‐BNPP)2]+ ( 2 ) (H L2 = 2,6‐bis‐[N,N‐di(2‐ pyridylmethyl)aminomethyl]‐4‐methylphenol, BNPP = bis(4‐nitrophenyl)phosphate) have been synthesized and their crystal structures and magnetic properties are shown. In 1 , each CoII atom has a distorted trigonal bipyramidal coordination sphere with a N3O2 donor set and the central two CoII atoms are bridged by one alkoxo‐O atom and one μ2‐DPP ion with the Co1‐Co2 separation of 3.542Å. In 2 , each CoII atom has a pseudo octahedral environment with a N3O3 donor set and the central two CoII atoms are bridged by a phenolic oxygen atom of L2 and two μ2‐BNPP ions with the Co1‐Co2 separation of 3.667Å. Susceptibility data of 1 and 2 indicate intramolecular antiferromagnetic coupling of the high‐spin CoII atoms. 相似文献
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Li‐Feng Tan Fang Wang Hui Chao Sheng Zhang Jun‐Jie Fei Liang‐Nian Ji 《Helvetica chimica acta》2008,91(7):1251-1260
A novel polypyridine ligand, dipyrido[3,2‐a:2′,3′‐c]phenazine‐11‐carboxylic acid methyl ester (=dppz‐11‐CO2Me), and its ruthenium(II) complex, [Ru(bpy)2(dppz‐11‐CO2Me)]2+ ( 1 ), were synthesized and characterized. The binding properties of this complex to calf‐thymus DNA (CT‐DNA) were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that the complex binds to DNA in an intercalative mode and serves as a molecular ‘light switch’ for DNA. When irradiated at 365 nm, the complex 1 promoted the photocleavage of plasmid pBR‐322 DNA. 相似文献
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A straightforward synthesis of orthogonally protected nucleoproline (Nup) amino acids and their coupling to oligomers are described. A key step is the attachment of alkynylated nucleobases to Fmoc‐protected 4‐azidoproline (Fmoc‐Azp‐OH) by a Cu‐catalyzed 1,3‐dipolar cycloaddition (‘click reaction’). The developed protocol allows preparation of the nucleoprolines in scales of >30 g. Solid‐phase peptide synthesis proved to be straightforward with these Nup amino acids. The resulting oligonucleoproline peptides adopt defined helices, are very well H2O soluble, and show comparable cell‐penetrating properties as recently reported α‐nucleoalanine peptides. 相似文献
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Kevin Salzmann Candela Segarra Martin Albrecht 《Angewandte Chemie (International ed. in English)》2020,59(23):8932-8936
An exceptionally efficient ruthenium‐based catalyst for olefin oxidation has been designed by exploiting N,N′‐bis(pyridylidene)oxalamide (bisPYA) as a donor‐flexible ligand. The dynamic donor ability of the bisPYA ligand, imparted by variable zwitterionic and neutral resonance structure contributions, paired with the redox activity of ruthenium provided catalytic activity for Lemieux–Johnson‐type oxidative cleavage of olefins to efficiently prepare ketones and aldehydes. The ruthenium bisPYA complex significantly outperforms state‐of‐the‐art systems and displays extraordinary catalytic activity in this oxidation, reaching turnover frequencies of 650 000 h?1 and turnover numbers of several millions. 相似文献
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Tomohiko Inagaki Le Thanh Phong Akihiro Furuta Jun‐ichi Ito Assist. Prof. Dr. Hisao Nishiyama Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(10):3090-3096
Chiral bis(oxazolinylphenyl)amines proved to be efficient auxiliary ligands for iron and cobalt catalysts with high activity for asymmetric hydrosilylation of ketones and asymmetric conjugate hydrosilylation of enones. 相似文献
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Qian‐Qian Lu Prof. Dr. Hai‐Zhu Yu Prof. Dr. Yao Fu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4584-4591
The mechanism of formic acid dehydrogenation catalyzed by the bis(imino)pyridine‐ligated aluminum hydride complex (PDI2?)Al(THF)H (PDI=bis(imino)pyridine) was studied by density functional theory calculations. The overall transformation is composed of two stages: catalyst activation and the catalytic cycle. The catalyst activation begins with O?H bond cleavage of HCOOH promoted by aluminum–ligand cooperation, followed by HCOOH‐assisted Al?H bond cleavage, and protonation of the imine carbon atom of the bis(imino)pyridine ligand. The resultant doubly protonated complex (H,HPDI)Al(OOCH)3 is the active catalyst for formic acid dehydrogenation. Given this, the catalytic cycle includes β‐hydride elimination of (H,HPDI)Al(OOCH)3 to produce CO2, and the formed (H,HPDI)Al(OOCH)2H mediates HCOOH to release H2. 相似文献
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Roberta Cacciapaglia Stefano Di Stefano Erik Kelderman Luigi Mandolini 《Angewandte Chemie (International ed. in English)》1999,38(3):348-351
Five components spontaneously self‐assemble to yield the productive complex 1 , where one barium ion delivers an ethoxide to the carbonyl group of an amide substrate anchored by means of a distal carboxylate moiety to the other barium ion. High substrate specificity, fairly high reaction rates with catalytic turnover, and competitive inhibition by inert substrates are observed. 相似文献
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An atom‐economic Pd0‐catalyzed synthesis of a series of pinacol‐type indolylboronates 3 from the corresponding bromoindole substrates 2 and pinacolborane (pinBH) as borylating agent was elaborated. The optimal catalyst system consisted of a 1 : 2 mixture of [Pd(OAc)2] and the ortho‐substituted biphenylphosphine ligand L‐3 (Scheme 4, Table). Our synthetic protocol was applied to the fast, preparative‐scale synthesis of 1‐substituted indolylboronates 3a – h in the presence of different functional groups, and at a catalyst load of only 1 mol‐% of Pd. 相似文献
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Keisuke Kato Prof. Satoshi Motodate Tomoyuki Mochida Prof. Takuya Kobayashi Hiroyuki Akita Prof. 《Angewandte Chemie (International ed. in English)》2009,48(18):3326-3328
Boxing clever : Direct conversion of a terminal alkyne group into a β‐methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid‐sensitive glycosidic bonds are not affected under the reaction conditions. The one‐pot synthesis of (±)‐dihydrokawain from the homopropargyl alcohol is also achieved. tfa=trifluoroacetate
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Zhenpin Lu Luca Schweighauser Dr. Heike Hausmann Prof. Dr. Hermann A. Wegner 《Angewandte Chemie (International ed. in English)》2015,54(51):15556-15559
The storage of energy in a safe and environmentally benign way is one of the main challenges of today’s society. Ammonia–borane (AB=NH3BH3) has been proposed as a possible candidate for the chemical storage of hydrogen. However, the efficient release of hydrogen is still an active field of research. Herein, we present a metal‐free bis(borane) Lewis acid catalyst that promotes the evolution of up to 2.5 equivalents of H2 per AB molecule. The catalyst can be reused multiple times without loss of activity. The moderate temperature of 60 °C allows for controlling the supply of H2 on demand simply by heating and cooling. Mechanistic studies give preliminary insights into the kinetics and mechanism of the catalytic reaction. 相似文献
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İsmail Özdemir Neslihan Şahin Bekir Çetinkaya 《Monatshefte für Chemie / Chemical Monthly》2007,138(3):205-209
Summary. Six [RuCl2(1-alkylbenzimidazole)(p-cymene)] complexes have been prepared and the new compounds characterized by C, H, N analyses, 1H NMR, and 13C NMR. The reduction of ketones to alcohols via transfer hydrogenation was achieved with catalytic amounts of the complexes in the presence of t-BuOK. 相似文献
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A novel class of chiral glycosyl‐triazole‐based P,N ligands were synthesized by ‘click chemistry’ and were applied to the Rh‐catalyzed asymmetric hydrosilylation of a range of substituted acetophenones. Enantioselective hydrosilylation of acetophenone gave (S)‐1‐phenylethanol in moderate enantioselectivity (72% ee) and in good conversion (93%). 相似文献
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Sachin Handa Prof. LeGrande M. Slaughter 《Angewandte Chemie (International ed. in English)》2012,51(12):3028-3028
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The asymmetric Friedel–Crafts alkylation of electron‐rich N‐containing heterocycles with nitroalkenes under catalysis of diphenylamine‐tethered bis(oxazoline) and bis(thiazoline)‐ZnII complexes was investigated. In the reaction of indole derivatives, the complex of ligand 4 f with trans‐diphenyl substitutions afforded better results than previously published ligand 4 e with cis‐diphenyl substitutions. Excellent yields (up to greater than 99 %) and enantioselectivities (up to 97 %) were achieved in most cases. The complex of ligand 4 d bearing tert‐butyl groups gave the best results in the reactions of pyrrole. Moderate to good yields (up to 91 %) and enantioselectivities (up to 91 %) were achieved in most cases. The origin of the enantioselectivity was attributed to the NH–π interaction between the catalyst and the incoming aromatic system in the transition state. Such an interaction was confirmed through comparison of the enantioselectivity and the absolute configuration of the products in the reactions catalyzed by designed ligands. 相似文献
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Highly Enantioselective Direct Synthesis of Endocyclic Vicinal Diamines through Chiral Ru(diamine)‐Catalyzed Hydrogenation of 2,2′‐Bisquinoline Derivatives 下载免费PDF全文
Wenpeng Ma Jianwei Zhang Cong Xu Fei Chen Yan‐Mei He Prof. Dr. Qing‐Hua Fan 《Angewandte Chemie (International ed. in English)》2016,55(41):12891-12894
An asymmetric hydrogenation of 2,2′‐bisquinoline and bisquinoxaline derivatives, catalyzed by chiral cationic ruthenium diamine complexes, was developed. A broad range of chiral endocyclic vicinal diamines were obtained in high yields with excellent diastereo‐ and enantioselectivity (up to 93:7 dl/meso and >99 % ee). These chiral diamines could be easily transformed into a new class of chiral N‐heterocyclic carbenes (NHCs), which are important but difficult to access. 相似文献