Lanthanide shift reagents. II. (a) Photochemical ring expansion of a .beta.-lactam and product identification using LSR [lanthanide shift reagents] NMR shifts and x-ray crystallography. (b) Probable structure of an LSR-substrate complex in solution. (c) Conformational analysis using LSR NMR data

1973 ◽  
Vol 95 (6) ◽  
pp. 1968-1977 ◽  
Author(s):  
Herman L. Ammon ◽  
Paul H. Mazzocchi ◽  
Walter J. Kopecky ◽  
Henry J. Tamburin ◽  
Plato H. Watts
Keyword(s):  
Ring Expansion ◽  
Probable Structure ◽  
Beta Lactam ◽  
X Ray ◽  
X Ray Crystallography ◽  
Substrate Complex ◽  
Nmr Data ◽  
Product Identification ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents

Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

2020 ◽  
Author(s):  
Marat Korsik ◽  
Edwin Tse ◽  
David Smith ◽  
William Lewis ◽  
Peter J. Rutledge ◽  
...  
Keyword(s):  
Heterocyclic Ring ◽  
Ring System ◽  
Substitution Reactions ◽  
Laboratory Notebook ◽  
Polar Solvents ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Core ◽  
Nmr Data

<p></p><p>We have discovered and studied a <i>tele</i>substitution reaction in a biologically important heterocyclic ring system. Conditions that favour the <i>tele</i>-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the <i>in vivo </i>active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium.</p> <p> </p> <p>Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds. </p><br><p></p>

scholarly journals Tris(phosphan)-Nickel(0)-Ethen-Komplexe (dmpe)(PR3)Ni(C2H4). Molekülstruktur des (dmpe)(PØ3 )Ni(C2H4)/ Tris(phosphane)-nickel(0)-ethene Complexes (dmpe)(PR3)Ni(C2H4). Molecular Structure of (dmpe)(PO3)Ni(C2H4)

1984 ◽  
Vol 39 (8) ◽  
pp. 1076-1081 ◽  
Author(s):  
Klaus R. Pörschke ◽  
Richard Mynott ◽  
Carl Krüger ◽  
M. J. Romão
Keyword(s):  
Molecular Structure ◽  
Ligand Exchange ◽  
Crystal And Molecular Structure ◽  
Exchange Reactions ◽  
Tetrahedral Geometry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nmr Data

AbstractSynthesis and properties of tris(phosphane)(ethene)nickel(0) complexes (dmpe)(PR3)Ni(C2H4) (R = CH3(4), c-C6H11(5), and C6H5 (6)) are reported. In solution. 4-6 are thermolabile and undergo ligand exchange reactions affording tetrakis(phosphane)nickel(0 ) and bis(phosphane)- (ethene)nickel(0) complexes. 1H, 13C, and 31P NMR data of 4-6 confirm the tetrahedral geometry around nickel. For 6 , the crystal and molecular structure has been determined by X-ray crystallography.

scholarly journals Coordination studies of 1,2-bis(diphenylphosphino)ethane with di-μ-hydroxo dinuclear complexes of tungsten(IV) and molybdenum(IV)

2016 ◽  
Vol 81 (1) ◽  
pp. 47-55
Author(s):  
Makoto Minato ◽  
Takashi Ito ◽  
Jian-Guo Ren
Keyword(s):  
31P Nmr ◽  
Product Distribution ◽  
Dinuclear Complex ◽  
Nucleophilic Attack ◽  
Dinuclear Complexes ◽  
X Ray ◽  
X Ray Crystallography ◽  
Phosphine Complexes ◽  
Nmr Data ◽  
Reaction Profile

The new trifluoroethoxo phosphine complexes [Cp2M(?1-dppe)(CF3CH2O)]+ and [Cp2(CF3CH2O)M(?-dppe)MCp2(CF3CH2O)]2+ (M = Mo or W, Cp = ?-C5H5 and dppe = Ph2PCH2CH2PPh2) have been prepared by reaction of cationic di-?-hydroxo dinuclear complex of molybdenocene or tungstenocene [Cp2M(?-OH)2MCp2]2+ with dppe. From the 1H and 31P NMR data, the configurations of the products could be assigned. Furtheremore, X-ray crystallography was used to definitively identify one of the product [Cp2(CF3CH2O)Mo(?-dppe)MoCp2(CF3CH2O)]2+, which crystallizes in space group P21/c(#14) with a = 12.230(5) ?, b = 11.149(5) ?, c = 28.966(7) ?, ? = 101.07(3)?, V = 3876(2) ?3, and Z = 2. It was ascertained that the amount of dppe added to the reaction mixture could influence the product distribution. A mechanism involving initial replacement of the hydroxo ligand by the alkoxo group followed by nucleophilic attack of the phosphine is proposed on the basis of the reaction profile.

Halogen substituted adamantanones. Structural studies with lanthanide shift reagents

1988 ◽  
Vol 53 (1) ◽  
pp. 97-109 ◽  
Author(s):  
Milan Hájek ◽  
Alena Horská ◽  
Petr Trška ◽  
Luděk Vodička ◽  
Douglas J. Raber ◽  
...  
Keyword(s):  
Bond Length ◽  
Optimization Procedure ◽  
Step Size ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Empirical Force Field ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents ◽  
Empirical Force Field Calculations

Europium shift reagents (both FOD and DPM) have been used to study a series of halogen substituted adamantanones by 1H NMR spectroscopy. Reliable correlations of molecular structure with the lanthanide induced shifts can be obtained only if certain precautions are taken. The source of atomic coordinates used to predict induced shifts with the pseudocontact equation is critical; coordinates by X-ray crystallography can be unreliable for this purpose, while those from empirical force field calculations yield satisfactory results. Determination of the europium-oxygen bond length by optimization of the agreement factor is shown to be inadequate. Even with a restricted Eu-O bond length, calculation of the best lanthanide position is shown to be dependent on the step size by which the lanthanide is moved in the optimization procedure. All of the compounds studied were found to give complexes with approximately linear C-O-Eu arrays, and the distortions from linearity are consistent with steric effects.

Cyclic Alkyl(aryl)boranes for 1,1-Carboboration of Monoalkynyltin Compounds

2013 ◽  
Vol 68 (5-6) ◽  
pp. 493-502 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Peter Thoma ◽  
Wolfgang Milius
Keyword(s):  
Solid State ◽  
High Selectivity ◽  
Ring Expansion ◽  
Membered Ring ◽  
Reaction Products ◽  
State Structure ◽  
Alkyl Aryl ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nmr Techniques

Two cyclic alkyl(aryl)boranes, a 1-bora-indane derivative 1, and a tricyclic derivative 4, containing the boron atom in a six-membered ring, were structurally characterized by NMR techniques in solution. The solid-state structure of the 1-bora-indane 1 was determined by X-ray crystallography. The reactivity of these cyclic alkyl(aryl)boranes towards monoalkynyltin compounds, Me3Sn-C≡C-Me and Me3Sn-C C-Fc (Fc=ferrocenyl), was studied using multinuclear magnetic resonance methods (1H, 11B, 13C, 119Sn NMR). Novel alkenylboranes were formed by 1,1-carboboration reactions. This process involves an expansion of both five- and six-membered rings. Insertion into the respective B-C(aryl) bond was preferred with high selectivity. In the case of the six-membered ring in 4, the ring expansion to seven-membered rings proved to be readily reversible, and the thermodynamically stable reaction products were formed by ring contraction and concomitant transfer of the exocyclic B-nPr group

Isobenzofulvenes. VIII. The structure of the dimers derived from 8,8-dimethylisobenzofulvene. A PMO treatment of the perispecificity in this dimerization and related cycloadditions involving isobenzofulvenes

1981 ◽  
Vol 34 (2) ◽  
pp. 397 ◽  
Author(s):  
RN Warrener ◽  
MN Paddon-Row ◽  
RA Russell ◽  
PL Watson
Keyword(s):  
Transition State ◽  
Structure Analysis ◽  
Chemical Degradation ◽  
Minor Isomer ◽  
X Ray ◽  
Firm Basis ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents

8,8-Dimethylisobenzofulvene, generated from the reaction of ll-isopropylidenetricyclo[6,2,1,02.7]- undeca-2,4,6,9-tetraene (23) and 3,6-di(pyridin-2-yl)-s-tetrazine, undergoes spontaneous dimerization to form a mixture of two isomers. This is shown to be a mixture of endo (33) and exo isomers (37) resulting from [π10s+π8s] cyclodimerization, with the former isomer predominating. 1H and 13C n.m.r. spectroscopy, in conjunction with lanthanide shift reagents and spin decoupling, was used, together with chemical degradation, to determine the structure and stereochemistry of these products. Chemical interconversion has placed these structures on a firm basis since the structure of the minor isomer has been determined by X-ray structure analysis. The constancy of this dimer ratio in solvents of widely differing polarity, and in the absence of solvent, supports an isopolar transition state which is typical of many concerted electrocyclic processes. A complete PMO treatment of all possible modes of isobenzofulvene dimerization is presented and the results of these calculations are discussed in terms of the observed peri- and stereospecificities. In a similar way, the PMO model is successfully employed to explain the relative efficiencies of various polyenophiles in trapping the isobenzofulvene nucleus.

Syntheses, characterization, and X-ray crystal structures of diorganotin(IV) derivatives of 2-pyridinethiolato-N-oxide

2003 ◽  
Vol 81 (10) ◽  
pp. 1070-1075 ◽  
Author(s):  
Chunlin Ma ◽  
Junhong Zhang ◽  
Rufen Zhang
Keyword(s):  
Crystal Structure ◽  
Stacking Interactions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nmr Data ◽  
Π Stacking ◽  
Oxide Crystal ◽  
Distorted Trigonal Bipyramid ◽  
Π Stacking Interaction ◽  
Derivatives Of

The diorganotin(IV) dichloride reacts with sodium 2-pyridinethiolato-N-oxide in a 1:1 ratio to produce [Me2SnCl(2-SpyO)] (1), [Et2SnCl(2-SpyO)] (2), [Bu2SnCl(2-SpyO)] (3), [Ph2SnCl(2-SpyO)] (4), and [(PhCH2)2SnCl(2- SpyO)] (5). The new complexes have been characterized by elemental analysis and IR and NMR (1H, 119Sn, and 13C) spectroscopy. On the basis of 119Sn NMR data the effective coordination number in solution is five. The structures 1 and 4 have been confirmed by X-ray crystallography. Crystals of 1 are triclinic with space group P[Formula: see text] and those of 4 are monoclinic, P21/n. The tin environment is a distorted trigonal bipyramid with the Cl and oxygen atoms in apical positions. Both complexes exhibit strong π–π stacking interactions. Key words: diorganotin, π–π stacking interaction, 2-pyridinethiolato-N-oxide, crystal structure.

scholarly journals New Tetramic Acid Derivatives From the Deep-Sea-Derived Fungus Penicillium sp. SCSIO06868 With SARS-CoV-2 Mpro Inhibitory Activity Evaluation

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiaoyan Pang ◽  
Weihao Chen ◽  
Xin Wang ◽  
Xuefeng Zhou ◽  
Bin Yang ◽  
...  
Keyword(s):  
Deep Sea ◽  
Optical Rotation ◽  
Ionization Mass ◽  
Tetramic Acid ◽  
Specific Optical Rotation ◽  
One Dimensional ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nmr Data ◽  
Main Protease

Three new tetramic acid derivatives (1–3) and a new polyketide (4) along with eight known compounds (5–12) were isolated from cultures of the deep-sea-derived fungus Penicillium sp. SCSIO06868. Four new structures were elucidated by analysis of one-dimensional/two-dimensional nuclear magnetic resonance (NMR) data and high-resolution electrospray ionization mass spectrometry. Their absolute configurations were established by X-ray crystallography analysis and comparison of the experimental and reported electronic circular dichroism (ECD) values or specific optical rotation. Compound 3 exhibited potent, selective inhibitory activities against Staphylococcus aureus and methicillin-resistant S. aureus with minimum inhibitory concentration values of both 2.5 μg/ml. Also, compound 3 showed weak antiviral activity against severe acute respiratory syndrome coronavirus 2 main protease, which was responsible for the coronavirus disease 2019 pandemic.

Sign in / Sign up

Export Citation Format

Share Document