Saegusa Oxidation of Enol Ethers at Extremely Low Pd-Catalyst Loadings under Ligand-free and Aqueous Conditions: Insight into the Pd(II)/Cu(II)-Catalyst System

2021 ◽  
Author(s):  
Quan Zhu ◽  
Yunsong Luo ◽  
Yongyan Guo ◽  
Yushun Zhang ◽  
Yunhai Tao
Keyword(s):  
Catalyst System ◽  
Pd Catalyst ◽  
Enol Ethers ◽  
Ligand Free ◽  
Aqueous Conditions ◽  
Insight Into

Experimental and computational evidence for C=O π-bonding in [CH2OH]+ and related oxonium ions

2020 ◽  
Vol 26 (3) ◽  
pp. 187-194
Author(s):  
Richard D Bowen ◽  
William HC Martin ◽  
Charles E Hudson ◽  
David J McAdoo
Keyword(s):  
Charge Distribution ◽  
Related Species ◽  
Experimental Information ◽  
Enol Ethers ◽  
Bond Lengths ◽  
Atoms And Molecules ◽  
Oxonium Ions ◽  
Insight Into ◽  
Oxygen Atoms

The question of whether [CH2OH]+ should be described as the hydroxymethyl cation, +CH2OH, or protonated formaldehyde, CH2=OH+, is reconsidered in the light of experimental information and new computational evidence. Previous arguments that the charge distribution in [CH2OH]+ may be probed by considering the incremental stabilisation of [CH2OH]+ induced by homologation on carbon (to give [CH3CHOH]+) or oxygen (to produce [CH2OCH3]+) are critically examined. Cation stabilisation energies are shown to be better indicators of the nature of these oxonium ions. Further insight into the structure of larger CnH2n+1O+ oxonium ions is obtained by considering the site of protonation of enol ethers and related species. Computational information, including AIM (Atoms and Molecules) and NBA (Natural Bond Analysis) charges on the carbon and oxygen atoms in [CH2OH]+ and related species, is considered critically. Particular attention is focused on the calculated bond lengths and barriers to rotation about the C–O bond(s) in [CH2OH]+, [CH3CHOH]+, [(CH3)2COH]+, CH3OH and [CH2OCH3]+ and the C–N bond in [CH2NH2]+. Trends in these data are consistent with appreciable π-bonding only in the C–O connections which correspond to the C=O bond in the parent aldehyde or ketone from which the oxonium ion may be considered to be derived by protonation or alkyl cationation.

PEPPSI-SONO-SP2: a new highly efficient ligand-free catalyst system for the synthesis of tri-substituted triazine derivatives via Suzuki–Miyaura and Sonogashira coupling reactions under a green approach

2016 ◽  
Vol 40 (6) ◽  
pp. 5135-5142 ◽  
Author(s):  
Motakatla Venkata Krishna Reddy ◽  
Peddiahgari Vasu Govardhana Reddy ◽  
Cirandur Suresh Reddy
Keyword(s):  
Palladium Catalyst ◽  
Cross Coupling ◽  
Catalyst System ◽  
Coupling Reactions ◽  
Sonogashira Coupling ◽  
Reaction Conditions ◽  
Cross Coupling Reactions ◽  
Green Approach ◽  
Ligand Free ◽  
Triazine Derivatives

Consecutive Suzuki–Miyaura and Sonogashira cross coupling reactions catalyzed by a new competent palladium catalyst PEPPSI-SONO-SP2 under mild and green reaction conditions.

scholarly journals Local Decomposition of Hybridization Functions: Chemical Insight into Correlated Molecular Adsorbates

2021 ◽  
Author(s):  
Marc Philipp Bahlke ◽  
Michaela Schneeberger ◽  
Carmen Herrmann
Keyword(s):  
Transition Metal ◽  
Kondo Effect ◽  
Valuable Insight ◽  
Cluster Approach ◽  
Molecular Adsorbates ◽  
Metal Atoms ◽  
Transition Metal Atoms ◽  
Ligand Free ◽  
Single Transition ◽  
Insight Into

Hybridization functions are an established tool for investigating the coupling between a correlated subsystem (often a single transition metal atom) and its uncorrelated environment (the substrate and any ligands present). The hybridization function can provide valuable insight into why and how strong correlation features such as the Kondo effect can be chemically controlled in certain molecular adsorbates. To deepen this insight, we introduce a local decomposition of the hybridization function, based on a truncated cluster approach, enabling us to study individual effects on this function coming from specific parts of the systems (e.g., the surface, ligands, or parts of larger ligands). It is shown that a truncated-cluster approach can reproduce the Co 3<em>d</em> and Mn 3<em>d</em> hybridization functions from periodic boundary conditions in Co(CO)<sub>4</sub>/Cu(001) and MnPc/Ag(001) qualitatively well. By locally decomposing the hybridization functions, it is demonstrated at which energies the transition metal atoms are mainly hybridized with the substrate or with the ligand. For the Kondo-active the 3d<sub>x2−y2</sub> orbital in Co(CO)<sub>4</sub>/Cu(001), the hybridization function at the Fermi energy is substrate-dominated, so we can assign its enhancement compared with ligand-free Co to an indirect effect of ligand–substrate interactions. In MnPc/Ag(001), the same is true for the Kondo-active orbital, but for two other orbitals, there are both direct and indirect effects of the ligand, together resulting in such strong screening that their potential Kondo activity is suppressed. A local decomposition of hybridization functions could also be useful in other areas, such as analyzing the electrode self-energies in molecular junctions.

scholarly journals Efficient nickel-catalysed N-alkylation of amines with alcohols

2018 ◽  
Vol 8 (21) ◽  
pp. 5498-5505 ◽  
Author(s):  
Anastasiia Afanasenko ◽  
Saravanakumar Elangovan ◽  
Marc C. A. Stuart ◽  
Giuseppe Bonura ◽  
Francesco Frusteri ◽  
...  
Keyword(s):  
Catalyst System ◽  
Highly Active ◽  
Ligand Free

A highly active and easy-to-prepare Ni based catalyst system is presented for the selective N-alkylation of amines with alcohols that is in situ generated from Ni(COD)2 and KOH under ligand-free conditions.

scholarly journals Relative to Quinine and Quinidine, Their 9-Epimers Exhibit Decreased Cytostatic Activity and Altered Heme Binding but Similar Cytocidal Activity versus Plasmodium falciparum

2012 ◽  
Vol 57 (1) ◽  
pp. 365-374 ◽  
Author(s):  
Alexander P. Gorka ◽  
Katy S. Sherlach ◽  
Angel C. de Dios ◽  
Paul D. Roepe
Keyword(s):  
Lethal Dose ◽  
Protoporphyrin Ix ◽  
Structural Diversity ◽  
Cytostatic Activity ◽  
Content Type ◽  
Article Type ◽  
Wide Range ◽  
Aqueous Conditions ◽  
Similar Affinity ◽  
Insight Into

ABSTRACTThe 9-epimers of quinine (QN) and quinidine (QD) are known to exhibit poor cytostatic potency againstP. falciparum(Karle JM, Karle IL, Gerena L, Milhous WK, Antimicrob. Agents Chemother. 36:1538–1544, 1992). We synthesized 9-epi-QN (eQN) and 9-epi-QD (eQD) via Mitsunobu esterification-saponification and evaluated both cytostatic and cytocidal antimalarial activities. Relative to the cytostatic activity of QN and QD, we observed a large decrease in cytostatic activity (higher 50% inhibitory concentration [IC50s]) against QN-sensitive strain HB3, QN-resistant strain Dd2, and QN-hypersensitive strain K76I, consistent with previous work. However, we observed relatively small changes in cytocidal activity (the 50% lethal dose), similar to observations with chloroquine (CQ) analogues with a wide range of IC50s (see the accompanying paper [A. P. Gorka, J. N. Alumasa, K. S. Sherlach, L. M. Jacobs, K. B. Nickley, J. P. Brower, A. C. de Dios, and P. D. Roepe, Antimicrob. Agents Chemother. 57:356–364, 2013]). Compared to QN and QD, the 9-epimers had significantly reduced hemozoin inhibition efficiency and did not affect pH-dependent aggregation of ferriprotoporphyrin IX (FPIX) heme. Magnetic susceptibility measurements showed that the 9-epimers perturb FPIX monomer-dimer equilibrium in favor of monomer, and UV-visible (VIS) titrations showed that eQN and eQD bind monomer with similar affinity relative to QN and QD. However, unique ring proton shifts in the presence of zinc(II) protoporphyrin IX (ZnPIX) indicate that binding of the 9-epimers to monomeric heme is via a distinct geometry. We isolated eQN- and eQD-FPIX complexes formed under aqueous conditions and analyzed them by mass, fluorescence, and UV-VIS spectroscopies. The 9-epimers produced low-fluorescent adducts with a 2:1 stoichiometry (drug to FPIX) which did not survive electrospray ionization, in contrast to QN and QD complexes. The data offer important insight into the relevance of heme interactions as a drug target for cytostatic versus cytocidal dosages of quinoline antimalarial drugs and further elucidate a surprising structural diversity of quinoline antimalarial drug-heme complexes.

New Tantalum Ligand-Free Catalyst System for Highly Selective Trimerization of Ethylene Affording 1-Hexene: New Evidence of a Metallacycle Mechanism

2009 ◽  
Vol 131 (15) ◽  
pp. 5370-5371 ◽  
Author(s):  
Rocío Arteaga-Müller ◽  
Hayato Tsurugi ◽  
Teruhiko Saito ◽  
Masao Yanagawa ◽  
Seiji Oda ◽  
...  
Keyword(s):  
Catalyst System ◽  
Ligand Free ◽  
New Evidence

scholarly journals Generation and agglomeration behaviour of size-selected sub-nm iron clusters as catalysts for the growth of carbon nanotubes

2011 ◽  
Vol 2 ◽  
pp. 734-739 ◽  
Author(s):  
Ravi Joshi ◽  
Benjamin Waldschmidt ◽  
Jörg Engstler ◽  
Rolf Schäfer ◽  
Jörg J Schneider
Keyword(s):  
Carbon Nanotubes ◽  
Iron Nanoparticles ◽  
Surface Coverage ◽  
Size Range ◽  
Iron Clusters ◽  
Median Size ◽  
Initial Cluster ◽  
Ligand Free ◽  
Cvd Growth ◽  
Insight Into

Mass-selected, ligand-free Fe N clusters with N = 10–30 atoms (cluster diameter: 0.6–0.9 nm) were implanted into [Al@SiO x ] surfaces at a low surface coverage corresponding to a few thousandths up to a few hundredths of a monolayer in order to avoid initial cluster agglomeration. These studies are aimed towards gaining an insight into the lower limit of the size regime of carbon nanotube (CNT) growth by employing size-selected sub-nm iron clusters as catalyst or precatalyst precursors for CNT growth. Agglomeration of sub-nm iron clusters to iron nanoparticles with a median size range between three and six nanometres and the CNT formation hence can be observed at CVD growth temperatures of 750 °C. Below 600 °C, no CNT growth is observed.

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