The Experts below are selected from a list of 5721 Experts worldwide ranked by ideXlab platform
David Milstein - One of the best experts on this subject based on the ideXlab platform.
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direct synthesis of amides by acceptorless dehydrogenative coupling of benzyl alcohols and ammonia catalyzed by a manganese Pincer Complex unexpected crucial role of base
2019Co-Authors: Prosenjit Daw, Yehoshoa Bendavid, Amit Kumar, Noel Angel Espinosajalapa, David MilsteinAbstract:Amide synthesis is one of the most important transformations in chemistry and biology. The direct use of ammonia for the incorporation of nitrogen functionalities in organic molecules is an attractive and environmentally benign method. We present here a new synthesis of amides by acceptorless dehydrogenative coupling of benzyl alcohols and ammonia. The reaction is catalyzed by a Pincer Complex of earth-abundant manganese in the presence of a stoichiometric base, making the overall process economical, efficient, and sustainable. Interesting mechanistic insights based on detailed experimental observations, indicating the crucial role of the base, are provided.
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acceptorless dehydrogenative coupling using ammonia direct synthesis of n heteroaromatics from diols catalyzed by ruthenium
2018Co-Authors: Prosenjit Daw, Yehoshoa Bendavid, David MilsteinAbstract:The synthesis of N-heteroaromatic compounds via an acceptorless dehydrogenative coupling process involving direct use of ammonia as the nitrogen source was explored. We report the synthesis of pyrazine derivatives from 1,2-diols and the synthesis of N-substituted pyrroles by a multicomponent dehydrogenative coupling of 1,4-diols and primary alcohols with ammonia. The acridine-based Ru-Pincer Complex 1 is an effective catalyst for these transformations, in which the acridine backbone is converted to an anionic dearomatized PNP-Pincer ligand framework.
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highly selective efficient deoxygenative hydrogenation of amides catalyzed by a manganese Pincer Complex via metal ligand cooperation
2018Co-Authors: Youquan Zou, Alexander Nerush, Yehoshoa Bendavid, Subrata Chakraborty, Dror Oren, Yael Diskinposner, David MilsteinAbstract:Deoxygenative hydrogenation of amides to amines homogeneously catalyzed by a Complex of an Earth-abundant metal is presented. This manganese-catalyzed reaction features high efficiency and selectivity. A plausible reaction mechanism, involving metal-ligand cooperation of the manganese Pincer Complex, is proposed based on NMR studies and relevant stoichiometric reactions.
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direct synthesis of amides by dehydrogenative coupling of amines with either alcohols or esters manganese Pincer Complex as catalyst
2017Co-Authors: Amit Kumar, Gregory Leitus, Noel Angel Espinosajalapa, Yael Diskinposner, Liat Avram, David MilsteinAbstract:The first example of base-metal-catalysed synthesis of amides from the coupling of primary amines with either alcohols or esters is reported. The reactions are catalysed by a new manganese Pincer Complex and generate hydrogen gas as the sole byproduct, thus making the overall process atom-economical and sustainable.
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synthesis of cyclic imides by acceptorless dehydrogenative coupling of diols and amines catalyzed by a manganese Pincer Complex
2017Co-Authors: Noel Angel Espinosajalapa, Gregory Leitus, Amit Kumar, Yael Diskinposner, David MilsteinAbstract:The first example of base-metal-catalyzed dehydrogenative coupling of diols and amines to form cyclic imides is reported. The reaction is catalyzed by a Pincer Complex of the earth abundant manganese and forms hydrogen gas as the sole byproduct, making the overall process atom economical and environmentally benign.
Kálmán J. Szabó - One of the best experts on this subject based on the ideXlab platform.
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selective c h borylation of alkenes by palladium Pincer Complex catalyzed oxidative functionalization
2010Co-Authors: Nicklas Selander, Benjamin Willy, Kálmán J. SzabóAbstract:The C—H borylation of simple alkenes catalyzed by a palladium Pincer Complex is performed in the presence of hypervalent iodine and bis(pinacolato)diboron.
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selective c h borylation of alkenes by palladium Pincer Complex catalyzed oxidative functionalization
2010Co-Authors: Nicklas Selander, Benjamin Willy, Kálmán J. SzabóAbstract:Selective C-H Borylation of Alkenes by Palladium Pincer Complex Catalyzed Oxidative Functionalization
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synthesis and transformation of organoboronates and stannanes by Pincer Complex catalysts
2010Co-Authors: Nicklas Selander, Kálmán J. SzabóAbstract:Palladium Pincer-Complexes readily catalyze the formation of allylstannanes, allenylstannanes/silanes and allylboronates from easily available allylic and propargylic substrates and dimetallic reagents. The catalytic activity and selectivity of the Pincer-Complexes can efficiently be fine-tuned by changing the heteroatoms in the side arms. Pincer-Complexes with nitrogen, sulfur and selenium atoms in the side arms are very efficient for creating C-Sn, C-Si and C-B bonds, while phosphorus based Complexes can be employed for catalytic cleavage of C-Sn and C-B bonds. Most of the catalytic metallation (stannylation and borylation) processes can easily be combined with other reactions, and thus one-pot procedures can be designed for the synthesis of homoallylic alcohols, homoallylic amines and alpha-amino acids from simple precursors.
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stereoselective Pincer Complex catalyzed c h functionalization of benzyl nitriles under mild conditions an efficient route to β aminonitriles
2009Co-Authors: Juhanes Aydin, Cathrin S Conrad, Kálmán J. SzabóAbstract:An efficient palladium Pincer-Complex catalyzed reaction has been developed for alpha-C-H bond functionalization of benzyl nitriles. The studied coupling reaction with sulfonylimines affords beta-aminonitriles with usually high levels of stereoselectivity. The stereoselectivity of the process is highly dependent on the electronic effects of the ortho substituents of the benzyl moiety. Promising levels of enantiomeric excess are obtained using chiral Pincer Complexes as catalysts.
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chiral palladium Pincer Complex catalyzed asymmetric condensation of sulfonimines and isocyanoacetate
2009Co-Authors: Juhanes Aydin, Andreas Ryden, Kálmán J. SzabóAbstract:This thesis is focused on the development of new Pincer Complex-catalyzed transformations. Optimization of the catalytic properties (fine-tuning) was directed to increase the catalytic activity as well as the chemo-, stereo- and enantioselectivity of the Complexes. This was achieved by varying the heteroatoms in the terdentate Pincer ligand, by changing the electronic properties of the coordinated aryl moiety and by implementing chiral functionalities in the Pincer Complexes. In the cross-coupling reaction of vinyl epoxides and aziridines with organoboronic acids the chemoselectivity of the reaction could be increased by employment of Pincer Complexes instead of commonly used Pd(0) catalysts. Furthermore, the introduction of a methoxy substituent in the aromatic subunit of the Complex considerably increased the activity of the Pincer Complex catalyst. Fine-tuning of the enantioselectivity in electrophilic allylation reactions was achieved by using a wide variety of new BINOL- and biphenanthrol-based Pincer Complexes. The highest enantioselectivity (85% ee) was obtained by applying biphenanthrol-based Pincer Complexes. Stereoselective Pincer Complex-catalyzed condensation of sulfonylimines with isocyanoacetate could be achieved under mild reaction conditions. By application of chiral PCP catalysts, 2-imidazolines could be obtained with up to 86% ee. A new Pincer Complex-catalyzed C-H bond functionalization based reaction between organonitriles and sulfonylimines affords homoallylic amines and beta-aminonitriles in high yields. The asymmetric version of this process affords beta-aminonitriles with up to 71% ee. In the last chapter, a Pincer Complex-catalyzed redox coupling reaction is described. In this highly regio- and stereoselective process the integrity of the Pincer catalysts is fully retained. This catalytic reaction proceeds with a high level of functional group tolerance, as allylic acetate and aryl halide functionalities are retained.
Yehoshoa Bendavid - One of the best experts on this subject based on the ideXlab platform.
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direct synthesis of amides by acceptorless dehydrogenative coupling of benzyl alcohols and ammonia catalyzed by a manganese Pincer Complex unexpected crucial role of base
2019Co-Authors: Prosenjit Daw, Yehoshoa Bendavid, Amit Kumar, Noel Angel Espinosajalapa, David MilsteinAbstract:Amide synthesis is one of the most important transformations in chemistry and biology. The direct use of ammonia for the incorporation of nitrogen functionalities in organic molecules is an attractive and environmentally benign method. We present here a new synthesis of amides by acceptorless dehydrogenative coupling of benzyl alcohols and ammonia. The reaction is catalyzed by a Pincer Complex of earth-abundant manganese in the presence of a stoichiometric base, making the overall process economical, efficient, and sustainable. Interesting mechanistic insights based on detailed experimental observations, indicating the crucial role of the base, are provided.
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acceptorless dehydrogenative coupling using ammonia direct synthesis of n heteroaromatics from diols catalyzed by ruthenium
2018Co-Authors: Prosenjit Daw, Yehoshoa Bendavid, David MilsteinAbstract:The synthesis of N-heteroaromatic compounds via an acceptorless dehydrogenative coupling process involving direct use of ammonia as the nitrogen source was explored. We report the synthesis of pyrazine derivatives from 1,2-diols and the synthesis of N-substituted pyrroles by a multicomponent dehydrogenative coupling of 1,4-diols and primary alcohols with ammonia. The acridine-based Ru-Pincer Complex 1 is an effective catalyst for these transformations, in which the acridine backbone is converted to an anionic dearomatized PNP-Pincer ligand framework.
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highly selective efficient deoxygenative hydrogenation of amides catalyzed by a manganese Pincer Complex via metal ligand cooperation
2018Co-Authors: Youquan Zou, Alexander Nerush, Yehoshoa Bendavid, Subrata Chakraborty, Dror Oren, Yael Diskinposner, David MilsteinAbstract:Deoxygenative hydrogenation of amides to amines homogeneously catalyzed by a Complex of an Earth-abundant metal is presented. This manganese-catalyzed reaction features high efficiency and selectivity. A plausible reaction mechanism, involving metal-ligand cooperation of the manganese Pincer Complex, is proposed based on NMR studies and relevant stoichiometric reactions.
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direct synthesis of symmetrical azines from alcohols and hydrazine catalyzed by a ruthenium Pincer Complex effect of hydrogen bonding
2016Co-Authors: Jonathan O Bauer, Gregory Leitus, Yehoshoa Bendavid, David MilsteinAbstract:Azines (2,3-diazabuta-1,3-dienes) are a widely used class of compounds with conjugated C═N double bonds. Herein, we present a direct synthesis of azines from alcohols and hydrazine hydrate. The reaction, catalyzed by a ruthenium Pincer Complex, evolves dihydrogen and can be run in a base-free version. The dehydrogenative coupling of benzylic and aliphatic alcohols led to good conversions and yields. Spectroscopic evidence for a hydrazine-coordinated dearomatized ruthenium Pincer Complex was obtained. Isolation of a supramolecular crystalline compound provided evidence for the important role of hydrogen bonding networks under the reaction conditions.
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template catalysis by metal ligand cooperation c c bond formation via conjugate addition of non activated nitriles under mild base free conditions catalyzed by a manganese Pincer Complex
2016Co-Authors: Alexander Nerush, Matthias Vogt, Urs Gellrich, Gregory Leitus, Yehoshoa Bendavid, David MilsteinAbstract:The first example of a catalytic Michael addition reaction of non-activated aliphatic nitriles to α,β-unsaturated carbonyl compounds under mild, neutral conditions is reported. A new de-aromatized pyridine-based PNP Pincer Complex of the Earth-abundant, first-row transition metal manganese serves as the catalyst. The reaction tolerates a variety of nitriles and Michael acceptors with different steric features and acceptor strengths. Mechanistic investigations including temperature-dependent NMR spectroscopy and DFT calculations reveal that the cooperative activation of alkyl nitriles, which leads to the generation of metalated nitrile nucleophile species (α-cyano carbanion analogues), is a key step of the mechanism. The metal center is not directly involved in the catalytic bond formation but rather serves, cooperatively with the ligand, as a template for the substrate activation. This approach of “template catalysis” expands the scope of potential donors for conjugate addition reactions.
Karl Heinz Dötz - One of the best experts on this subject based on the ideXlab platform.
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a pyridine bridged bis benzimidazolylidene Pincer nickel ii Complex synthesis and practical catalytic application towards suzuki miyaura coupling with less activated electrophiles
2010Co-Authors: Han Mao, Christian Herbert, Karl Heinz DötzAbstract:A novel robust pyridine-bridged bis-benzimidazolylidene nickel Pincer Complex 3 accessible from inexpensive, commercially available precursors efficiently catalyzes the first practical Suzuki–Miyaura cross-coupling reactions with various less-reactive electrophiles ArX (X = Br, Cl, OTs and OMs) and even tolerates electron-rich, sterically demanding and heterocyclic arenes in the presence of catalytic amounts of PPh3.
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A Novel Pyridine-Bridged Bis-benzimidazolylidene Pincer Palladium Complex : Synthesis and Catalytic Properties
2008Co-Authors: Jagadeesh Malineni, Karl Heinz DötzAbstract:A novel pyridine-bridged bis-benzimidazolylidene CNC Pincer Complex 1 was synthesized from cheap, commercially available precursors under microwave assistance in moderate yield. It catalyzes cross-coupling reactions of aryl halides with alkyl acrylates (Heck reaction) and phenylboronic acid (Suzuki reaction) under aerobic conditions with extremely high turn-over numbers (frequencies) indicating that a planar extension of the π-system by benzannelation significantly increases the catalytic activity even with trace amounts of catalyst loading.
Nicolas Boutin - One of the best experts on this subject based on the ideXlab platform.
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suzuki miyaura cross coupling reactions of unactivated alkyl halides catalyzed by a nickel Pincer Complex
2014Co-Authors: Thomas Di Franco, Nicolas BoutinAbstract:A Nickel Pincer Complex is used to catalyze alkyl—alkyl and alkyl—aryl Suzuki—Miyaura cross coupling reactions of unactivated alkyl halides (I).
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suzuki miyaura cross coupling reactions of unactivated alkyl halides catalyzed by a nickel Pincer Complex
2013Co-Authors: Thomas Di Franco, Nicolas BoutinAbstract:A nickel(II) Pincer Complex, [(MeN2N)Ni-Cl], was used to catalyze alkyl–alkyl and alkyl–aryl Suzuki–Miyaura coupling reactions of unactivated alkyl halides. The coupling of 9-alkyl-9-borabicyclo[3.3.1]nonane and 9-phenyl-9-borabicyclo[3.3.1]nonane reagents with alkyl halides was achieved in modest to good yields. The reactions tolerated a variety of useful functional groups including ester, ether, furan, thioether, acetal, and Boc groups.
