The use of a chiral borate counteranion as a 1H NMR shift reagent for cationic copper(I) complexes

2003 ◽  
Vol 81 (11) ◽  
pp. 1280-1284 ◽  
Author(s):  
David B Llewellyn ◽  
Bruce A Arndtsen
Keyword(s):  
Key Words ◽  
Asymmetric Catalysis ◽  
1H Nmr ◽  
Copper Complex ◽  
Ion Pairing ◽  
Shift Reagent ◽  
Copper Salt ◽  
Chiral Ligands ◽  
H Nmr ◽  
Wide Range

The chiral borate counteranion bis[(R)-1,1′-bi-2-naphtholato]borate (1–) has been found to be a competent chiral 1H NMR shift reagent for cationic copper(I) complexes. This has been demonstrated by the addition of the Cu(NCMe)4+ salt of 1– to two classes of common chiral ligands in asymmetric catalysis: 2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl (tol-BINAP) (2) and 2,2′-isopropylidenebis(4-phenyl-2-oxazoline) (3). In the case of ligand 2, the addition of 1 equiv. of either (R,R)-2 or (S,S)-2 to Cu(NCMe)4+1– results in well-resolved 1H NMR resonances for the two enantiomers. Examination of standard solutions of non-enantiopure 2 shows that the copper complex can be an effective NMR shift reagent of a wide range of enantiomeric compositions. Cu(NCMe)4+1– also generates distinct 1H NMR resonances for the two separate enantiomers of 2,2′-isopropylidenebis(4-phenyl-2-oxazoline) (3). However, attempts to employ this copper salt as a chiral NMR shift reagent for rac-3 led to the discovery of a new and unexpected equilibrium: [(R,R)-3]Cu+ + [(S,S)-3]Cu+ [Formula: see text] [(R,R)-3][(S,S)-3]Cu+ + Cu+. Key words: chiral counteranion, copper, chiral NMR shift reagent, ion pairing.

1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Part II: Ethosuximide, 3-Ethyl-3-Methyl-2,5-Pyrrolidinedione, and Comparisons with Analogs

1986 ◽  
Vol 40 (4) ◽  
pp. 531-537 ◽  
Author(s):  
John Avolio ◽  
Suzanne Thomson Eberhart ◽  
Robert Rothchild ◽  
Paul Simons
Keyword(s):  
1H Nmr ◽  
Nmr Spectra ◽  
Shift Reagent ◽  
Ethyl Group ◽  
Molar Ratios ◽  
H Nmr ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents

The 60 MHz 1H NMR spectra of racemic ethosuximide, 1, have been studied in detail with the achiral shift reagent, tris(6,6,7,7,8,8,8-hepta-fiuoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, and the chiral tris(3-trifluoromethylhydroxymethylene)- d-camphorato]europium(III), 3. Enantiomeric shift differences, ΔΔδ, were clearly observed for the CH3 of the ethyl group of 1 at molar ratios of 3:1 as low as 0.0385, with ΔΔδ valaues of about 12 Hz seen at a 3:1 ratio of 0.340 for CDCl3 solutions at 28°, 0.634 molal in 1. Smaller ΔΔδ values were also seen for the quaternary methyl and for one of the hydrogens at C-4. Parallel studies with 2 were performed to support assignments. Results are compared with a group of important drugs that are structurally related, including ethotoin, mephenytoin, glutethimide, methsuximide, phensuximide, and paramethadione, in terms of steric and basicity effects. Correlations of both lanthanide-induced shift (Δδ) and ΔΔδ could generally be made from simple electronic considerations related to infrared carbonyl stretching frequencies. Of the 28 sets of Δδ values assigned for the substrates, 3 gave significantly larger values than 2 in only two cases.

Optical Purity Determination and 1H NMR Spectral Simplification with Lanthanide Shift Reagents III: Ethotoin, 3-Ethyl-5-Phenyl-2, 4-Imidazolidinedione

1984 ◽  
Vol 38 (5) ◽  
pp. 734-737 ◽  
Author(s):  
John Avolio ◽  
Robert Rothchild
Keyword(s):  
1H Nmr ◽  
Nmr Spectra ◽  
Optical Purity ◽  
Shift Reagent ◽  
Methine Proton ◽  
Molar Ratio ◽  
Purity Determination ◽  
H Nmr ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents

The 60 MHz 1H NMR spectra of racemic ethotoin, a, have been studied with the achiral shift reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimeth-yl-3,5-octanedionato) europium (III), b, and the chiral tris[3-(rrifluoromethylhydroxymethylene)- d-camphorato] europium (III), c Appreciable values of the enantiomeric shift difference, ΔΔδ, were observed for the NH, CH3, CH, and ortho aryl protons in CDCl3 solutions at 28°C with the use of samples about 045 molal in a Optical purity assays should be feasible with the use of the NH or CH3 absorptions that display ΔΔδ of 224 and 70 Hz, respectively, at a c:a molar ratio of about 03, with the former resonance being optimal With a c:a ratio between 04–05, the methine proton can be used, with ΔΔδ 11 – 13 Hz Results are interpreted in terms of major coordination of the europium at the C-2 oxygen

Solvent-Ligand Interactions in Colloidal Nanocrystals

2018 ◽  
Author(s):  
Jonathan De Roo ◽  
Nuri Yazdani ◽  
Emile Drijvers ◽  
Alessandro Lauria ◽  
Jorick Maes ◽  
...  
Keyword(s):  
Direct Method ◽  
Line Broadening ◽  
H Nmr ◽  
Size Dependent ◽  
Line Shape Analysis ◽  
Wide Range ◽  
Nanocrystal Synthesis ◽  
Ligand Interactions ◽  
Indispensable Tool ◽  
Theoretical Evidence

<p>Although solvent-ligand interactions play a major role in nanocrystal synthesis, dispersion formulation and assembly, there is currently no direct method to study this. Here we examine the broadening of <sup>1</sup>H NMR resonances associated with bound ligands, and turn this poorly understood descriptor into a tool to assess solvent-ligand interactions. We show that the line broadening has both a homogeneous and a heterogeneous component. The former is nanocrystal-size dependent and the latter results from solvent-ligand interactions. Our model is supported by experimental and theoretical evidence that correlates broad NMR lines with poor ligand solvation. This correlation is found across a wide range of solvents, extending from water to hexane, for both hydrophobic and hydrophilic ligand types, and for a multitude of oxide, sulfide and selenide nanocrystals. Our findings thus put forward NMR line shape analysis as an indispensable tool to form, investigate and manipulate nanocolloids.</p>

Novel Chiral Ligands for Palladium-catalyzed Asymmetric Allylic Alkylation/ Asymmetric Tsuji-Trost Reaction: A Review

2019 ◽  
Vol 23 (11) ◽  
pp. 1168-1213 ◽  
Author(s):  
Samar Noreen ◽  
Ameer Fawad Zahoor ◽  
Sajjad Ahmad ◽  
Irum Shahzadi ◽  
Ali Irfan ◽  
...  
Keyword(s):  
Asymmetric Catalysis ◽  
Enantioselective Synthesis ◽  
Chiral Ligands ◽  
Allylic Alkylation ◽  
Research Groups ◽  
Asymmetric Allylic Alkylation ◽  
Catalytic Potential ◽  
Long Time ◽  
Palladium Catalyzed ◽  
Alkylation Reactions

Background: Asymmetric catalysis holds a prestigious role in organic syntheses since a long time and chiral inductors such as ligands have been used to achieve the utmost desired results at this pitch. The asymmetric version of Tsuji-Trost allylation has played a crucial role in enantioselective synthesis. Various chiral ligands have been known for Pdcatalyzed Asymmetric Allylic Alkylation (AAA) reactions and exhibited excellent catalytic potential. The use of chiral ligands as asymmetric inductors has widened the scope of Tsuji-Trost allylic alkylation reactions. Conclusion: Therefore, in this review article, a variety of chiral inductors or ligands have been focused for palladium catalyzed asymmetric allylic alkylation (Tsuji-Trost allylation) and in this regard, recently reported literature (2013-2017) has been described. The use of ligands causes the induction of enantiodiscrimination to the allylated products, therefore, the syntheses of various kinds of ligands have been targeted by many research groups to employ in Pd-catalyzed AAA reactions.

Application of Nitrogen Heterocyclic Carbenes in Organocatalysis

2020 ◽  
Vol 09 ◽  
Author(s):  
Minita Ojha ◽  
R. K. Bansal
Keyword(s):  
Asymmetric Catalysis ◽  
Building Blocks ◽  
Structural Features ◽  
Heterocyclic Carbenes ◽  
Stetter Reaction ◽  
Metal Pollutants ◽  
Synthetic Strategy ◽  
Wide Range ◽  
Benzoin Condensation ◽  
Nitrogen Heterocyclic

Background: During the last two decades, horizon of research in the field of Nitrogen Heterocyclic Carbenes (NHC) has widened remarkably. NHCs have emerged as ubiquitous species having applications in a broad range of fields, including organocatalysis and organometallic chemistry. The NHC-induced non-asymmetric catalysis has turned out to be a really fruitful area of research in recent years. Methods: By manipulating structural features and selecting appropriate substituent groups, it has been possible to control the kinetic and thermodynamic stability of a wide range of NHCs, which can be tolerant to a variety of functional groups and can be used under mild conditions. NHCs are produced by different methods, such as deprotonation of Nalkylhetrocyclic salt, transmetallation, decarboxylation and electrochemical reduction. Results: The NHCs have been used successfully as catalysts for a wide range of reactions making a large number of building blocks and other useful compounds accessible. Some of these reactions are: benzoin condensation, Stetter reaction, Michael reaction, esterification, activation of esters, activation of isocyanides, polymerization, different cycloaddition reactions, isomerization, etc. The present review includes all these examples published during the last 10 years, i.e. from 2010 till date. Conclusion: The NHCs have emerged as versatile and powerful organocatalysts in synthetic organic chemistry. They provide the synthetic strategy which does not burden the environment with metal pollutants and thus fit in the Green Chemistry.

Conformational study on ribonucleoside O-phosphonylmethyl derivatives by 1H NMR spectroscopy

1985 ◽  
Vol 50 (8) ◽  
pp. 1899-1905 ◽  
Author(s):  
Milena Masojídková ◽  
Jaroslav Zajíček ◽  
Miloš Buděšínský ◽  
Ivan Rosenberg ◽  
Antonín Holý
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Conformational Study ◽  
H Nmr ◽  
Conformational Properties

Conformational properties of ribonucleoside 5'-O-phosphonylmethyl derivatives have been determined by 1H NMR spectroscopy and compared with those of natural nucleosides and 5'-nucleotides.

119Sn, 13C and 1H NMR Spectra of Tris(1-butyl)stannyl D-Glucuronate

1997 ◽  
Vol 62 (8) ◽  
pp. 1169-1176 ◽  
Author(s):  
Antonín Lyčka ◽  
Jaroslav Holeček ◽  
David Micák
Keyword(s):  
Chemical Shift ◽  
Carbonyl Group ◽  
1H Nmr ◽  
Equatorial Plane ◽  
Title Compound ◽  
Nmr Spectra ◽  
Hydroxyl Groups ◽  
Carboxylic Group ◽  
H Nmr ◽  
Oxygen Atoms

The 119Sn, 13C and 1H NMR spectra of tris(1-butyl)stannyl D-glucuronate have been measured in hexadeuteriodimethyl sulfoxide, tetradeuteriomethanol and deuteriochloroform. The chemical shift values have been assigned unambiguously with the help of H,H-COSY, TOCSY, H,C-COSY and 1H-13C HMQC-RELAY. From the analysis of parameters of 119Sn, 13C and 1H NMR spectra of the title compound and their comparison with the corresponding spectra of tris(1-butyl)stannyl acetate and other carboxylates it follows that in solutions of non-coordinating solvents (deuteriochloroform) the title compound is present in the form of more or less isolated individual molecules with pseudotetrahedral environment around the central tin atom and with monodentately bound carboxylic group. The interaction of tin atom with oxygen atoms of carbonyl group and hydroxyl groups of the saccharide residue - if they are present at all - are very weak. In solutions in coordinating solvents (hexadeuteriodimethyl sulfoxide or tetradeuteriomethanol), the title compound forms complexes with one molecule of the solvent. Particles of these complexes have a shape of trigonal bipyramid with the 1-butyl substituents in equatorial plane and the oxygen atoms of monodentate carboxylic group and coordinating solvent in axial positions.

A 15N, 13C, and 1H NMR study of reaction products from arylguanidines and chloroformate esters

1991 ◽  
Vol 56 (7) ◽  
pp. 1505-1511 ◽  
Author(s):  
Antonín Lyčka ◽  
Karel Palát
Keyword(s):  
1H Nmr ◽  
Nmr Spectra ◽  
Reaction Products ◽  
H Nmr ◽  
Nmr Study

The 15N, 13C, and 1H NMR spectra of the reaction products from arylguanidines with two mols of chloroformate esters have been measured. With application of the corresponding 15N isotopomer it has been proved that the reaction products have the structures IIIa-IIIc.

Synthesis and characterization of novel chiral derivatizing agents containing β-keto-anthracene adducts (KAAs) by 1H-NMR: aromatic influence and chiral alcohol absolute configuration determination

2019 ◽  
Vol 17 (3) ◽  
pp. 541-554
Author(s):  
Neeranuth Intakaew ◽  
Puracheth Rithchumpon ◽  
Chanatkran Prommin ◽  
Saranphong Yimklan ◽  
Nawee Kungwan ◽  
...  
Keyword(s):  
1H Nmr ◽  
Absolute Configuration ◽  
Synthesis And Characterization ◽  
Chiral Alcohols ◽  
Chiral Alcohol ◽  
Aromatic Rings ◽  
H Nmr ◽  
Chiral Derivatizing Agents

New chiral derivatizing agents and the effect of aromatic rings were investigated for absolute configuration of chiral alcohols via1H-NMR.

Different submicellar solubilization mechanisms revealed by 1H NMR and 2D diffusion ordered spectroscopy (DOSY)

2020 ◽  
Vol 22 (19) ◽  
pp. 11075-11085
Author(s):  
Mengjian Wu ◽  
Zhaoxia Wu ◽  
Shangwu Ding ◽  
Zhong Chen ◽  
Xiaohong Cui
Keyword(s):  
Nmr Spectroscopy ◽  
Sodium Dodecyl Sulfate ◽  
1H Nmr ◽  
Sodium Dodecyl ◽  
Butyl Methacrylate ◽  
H Nmr ◽  
Molecular Scale ◽  
Two Systems ◽  
Dodecyl Sulfate ◽  
Triton X

Different submicellar solubilization mechanisms of two systems, Triton X-100/tetradecane and sodium dodecyl sulfate (SDS)/butyl methacrylate, are revealed on the molecular scale by 1H NMR spectroscopy and 2D diffusion ordered spectroscopy (DOSY).

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