Organosulfur oxoacids. Part 1. Synthesis, structure, and reactivity of dimethylaminoiminomethanesulfinic acid (DMAIMSA)

2006 ◽  
Vol 84 (5) ◽  
pp. 825-830 ◽  
Author(s):  
Jonathan F Ojo ◽  
Jeffrey L Petersen ◽  
Adenike Otoikhian ◽  
Reuben H Simoyi
Keyword(s):  
Sulfonic Acid ◽  
Positive Charge ◽  
Strictly Anaerobic ◽  
Single Bond ◽  
Anaerobic Conditions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Acidic Conditions ◽  
The One ◽  
Solid Form

One of the major metabolites of dimethylthiourea, dimethylaminoiminomethanesulfinic acid (DMAIMSA), was synthesized by controlled oxidation of dimethylthiourea using hydrogen peroxide. The crystal structure was determined by X-ray crystallography. It is a zwitterionic species in its solid form, with a positive charge delocalized around an sp2-hybridized carbon center and two nitrogen atoms. It crystallizes in the triclinic P[Formula: see text] space group. The C—S bond, at 1.880(2) Å, is much longer than a typical C—S single bond length of 1.79 Å. It is also longer than the one observed in thiourea trioxide, a comparable sulfonic acid. This C—S bond is stable in acidic conditions and is easily cleaved in basic conditions or in the presence of suitable nucleophiles that can attack the positively disposed carbon center. DMAIMSA is highly reactive and easily decomposes in basic conditions to yield dithionite in the presence of oxygen, whereas in strictly anaerobic conditions it gives a mixture of sulfite and sulfide. The precursor to dithionite, SO2·–, is formed from the one-electron oxidation of the sulfoxylate anion, SO22–, which results from an initial heterolytic cleavage of the C—S bond in DMAIMSA. The sulfur center is oxidized, even by mild oxidants such as aqueous iodine, to sulfate. Key words: thiourea metabolites, synthesis, structure, reactivity.

A Facile Synthesis of a 2,2,3,3-Tetrasubstituted Tetrahydropyran

1991 ◽  
Vol 44 (8) ◽  
pp. 1115
Author(s):  
DJ Brecknell ◽  
RM Carman ◽  
WT Robinson ◽  
RC Schumann
Keyword(s):  
Major Product ◽  
Single Bond ◽  
Facile Synthesis ◽  
X Ray ◽  
X Ray Crystallography

An unusually facile acid- catalysed condensation has been observed between acetone and the unsaturated diol (3), producing a mixture of isomeric bicyclic tetrahydropyrans (6) and (8), with the formation of a new fully substituted carbon-carbon single bond. The structures were determined by n.m.r. and that of the major product (6) was confirmed by X-ray crystallography.

Synthesis and properties of a corrole with small and electron-withdrawing substitutents, 5,15-bis(trifluoromethyl)-10-pentafluorophenylcorrole

2006 ◽  
Vol 10 (02) ◽  
pp. 76-86 ◽  
Author(s):  
Ruth Goldschmidt ◽  
Israel Goldberg ◽  
Yael Balazs ◽  
Zeev Gross
Keyword(s):  
X Ray ◽  
X Ray Crystallography ◽  
The One ◽  
Electron Withdrawing Substituents

Several methodologies for the synthesis of corroles that carry minimal-sized electron-withdrawing substituents at the meso- C atoms were investigated; of these the one based on dypyrromethane/aldehyde condensation was fruitful. The new corrole with one C 6 F 5 and two CF 3 groups, as well as its cobalt(III) complex, were fully characterized by spectroscopy and X-ray crystallography.

Synthesis and characterization of β,β′-linked porphyrin-chlorin heterodimers and their metallic complexes

2017 ◽  
Vol 21 (03) ◽  
pp. 211-221
Author(s):  
Congcong Zhuo ◽  
Caifen Ou ◽  
Chuanjiang Hu ◽  
Jianping Lang
Keyword(s):  
Copper Complexes ◽  
Close Contact ◽  
Dihedral Angles ◽  
Single Bond ◽  
X Ray ◽  
X Ray Crystallography ◽  
Uv Visible ◽  
Text Interaction ◽  
Porphyrin Moiety

Two β,β′-linked porphyrin-chlorin heterodimers have been successfully synthesized with 4-fluorophenyl or 4-chlorophenyl substituted aldehyde as starting reagents. But those aldehydes with bulkier substituents did not lead to the corresponding heterodimers. These porphyrin-chlorin heterodimers and their metallic complexes have been characterized by X-ray crystallography. In all the structures, the pyrroline group in chlorin moiety and the pyrrole group in porphyrin moiety are directly connected by a single bond. Pyrroline ring has two sp[Formula: see text] hybridized carbons. The direct bonding makes the porphyrin and chlorin moieties closely contact with each other, pyrroline group and the pyrrole group forms a dihedral angle of ~70°. If porphyrin-chlorin heterodimers have bulkier substituents, the close contact could cause too much repulsion. That is probably why they can not be synthesized. For nickel complexes, the chlorin planes show large saddling and moderate ruffling conformation. The C–H⋯[Formula: see text] interaction could contribute to the saddling conformation. The distorted core makes dihedral angles and metal to metal distances between porphyrin and chlorin plane much smaller than those in their copper complexes. Their NMR, UV-visible and fluorescence spectral data have also been briefly discussed.

scholarly journals Polymorphism in Griseofulvin: New Story of an Old Drug with Polyethylene Glycol

2021 ◽  
Author(s):  
Xiao Ou ◽  
Shuting Li ◽  
Yunyun Chen ◽  
Haowei Rong ◽  
Ao Li ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Solid Dispersions ◽  
Melt Crystallization ◽  
X Ray ◽  
X Ray Crystallography ◽  
Polymer Addition ◽  
Single Crystal Structures ◽  
Solid Form ◽  
First Time ◽  
And Storage

Griseofulvin (GSF) is an antifungal drug that has been clinically used for six decades. Here, we present a rich polymorphism of GSF crystallizing from GSF dispersions with polyethylene glycol (PEG), including five true polymorphs (Forms I-V) and one inclusion complex (IC). Two new polymorphs were reported for the first time, denoted Forms IV and V. Single-crystal structures of new polymorphs and a GSF-PEG IC were determined by X-ray crystallography using single crystals cultivated by microdroplet melt crystallization. A comprehensive solid form landscape of GSF is established to describe phase conversions between polymorphs. Enhancement in molecular mobility by PEG is suggested to be the reason for the nucleation of two new polymorphs, while the small geographic radius of PEG is attributed to the formation of a GSF-PEG IC increasing the density and lowering the Gibbs free energy of the system. This work expands our understanding of the complicated crystallization behavior of GSF in dispersions with PEG and emphasizes the importance of polymorphism control during the manufacturing and storage of PEG-based solid dispersions to achieve reproducible and consistent pharmaceutical performance. The results also suggest that polymer addition is an alternative strategy that cannot be neglected in polymorphism screening.

scholarly journals Synthesis and Characterization of Unsymmetrical Double-Decker Siloxane (Basket Cage)

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4252 ◽  
Author(s):  
Rungthip Kunthom ◽  
Nobuhiro Takeda ◽  
Masafumi Unno
Keyword(s):  
29Si Nmr ◽  
Cage Compounds ◽  
One Pot ◽  
X Ray ◽  
X Ray Crystallography ◽  
Double Decker ◽  
Novel Structure ◽  
The One ◽  
First Time

The one-pot synthesis of an unsymmetrical double-decker siloxane with a novel structure via the reaction of double-decker tetrasodiumsilanolate with 1 equiv. of dichlorotetraphenyldisiloxane in the presence of an acid is reported herein for the first time. The target compound bearing all phenyl substituents on the unsymmetrical siloxane structure was successfully obtained, as confirmed by 1H-NMR, 13C-NMR, 29Si-NMR, IR, MALDI-TOF, and X-ray crystallography analyses. Additionally, the thermal properties of the product were evaluated by TG/DTA and compared with those of other siloxane cage compounds.

Structural, electrochemical and photochemical investigation of the water-soluble tin(IV) tetrakis(2-N-hydroxyethyl-4-pyridinium)porphyrin photocatalyst

2011 ◽  
Vol 15 (11n12) ◽  
pp. 1345-1353 ◽  
Author(s):  
Luuk L. C. Olijve ◽  
Ethan N. W. How ◽  
Mohan Bhadbhade ◽  
Shiva Prasad ◽  
Stephen B. Colbran ◽  
...  
Keyword(s):  
Radical Anion ◽  
Main Product ◽  
Differential Pulse ◽  
Water Soluble ◽  
Anaerobic Conditions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Electrochemical Processes ◽  
Pulse Voltammetry ◽  
Apparent Ability

The water-soluble tin(IV) tetrakis(2-N-hydroxyethyl-4-pyridinium)porphyrin 1 photocatalyst was synthesized in good yield and its structure determined by single crystal X-ray crystallography. Electrochemical measurements on tin(IV) porphyrin 1 reveal a range of complex redox processes that are highly dependent on the pH and electrode used. The cathodic processes at ca. -0.6 to -0.8 V were assigned to electrochemical processes on the pyridyl moiety following differential pulse voltammetry and spectroelectrochemical investigation into the electrochemical properties of tin(IV) porphyrin. Photocatalytic experiment on tin(IV) porphyrin 1 under anaerobic conditions using triethanolamine (TEAO) as a sacrifical donor reveal a phlorin species as the main product which rapidly disappears upon exposure to oxygen. These results suggest that tin(IV) porphyrin π-radical anion is perhaps not the species responsible for the apparent ability tin(IV) porphyrins to photocatalytically reduce various substrates, including water to hydrogen.

scholarly journals Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

2019 ◽  
Vol 15 ◽  
pp. 1347-1354
Author(s):  
Andrew T King ◽  
Hugh G Hiscocks ◽  
Lidia Matesic ◽  
Mohan Bhadbhade ◽  
Roger Bishop ◽  
...  
Keyword(s):  
Single Crystal ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
One Pot ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
X Ray Crystallography ◽  
The One ◽  
Close Contacts

The one-pot reaction of 2,6-bis(diphenylmethyl)-4-methoxyaniline with tert-butylnitrite, BTEAC and DABSO in the presence of CuCl2 provided an unexpected 3H-indazole product 8. The structure of the compound was determined by HRMS, IR, NMR and further confirmed by single crystal X-ray crystallography. The compound crystallises in the triclinic P-1 space group, with unit cell parameters a = 9.2107 (4), b = 10.0413 (5), c = 14.4363 (6) Å, α = 78.183 (2), β = 87.625 (2), γ = 71.975 (2)°. The formation of 8 proceeded through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate 9. The molecules of 8 are organised by edge–face Ar–H···π, face–face π···π, and bifurcated OCH2–H···N interactions. In addition to these, there are Ar–H···H–Ar close contacts, (edge–edge and surrounding inversion centres) arranged as infinite tapes along the a direction.

scholarly journals Replacement of the Common Chromium Source CrCl3(thf)3 with Well-Defined [CrCl2(μ-Cl)(thf)2]2

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1167
Author(s):  
Dong Geun Lee ◽  
Jun Won Baek ◽  
Jung Hyun Lee ◽  
Hyun Ju Lee ◽  
Yeong Hyun Seo ◽  
...  
Keyword(s):  
Structure Determination ◽  
Starting Material ◽  
Crystalline Solid ◽  
Minimal Amount ◽  
Xrd Pattern ◽  
X Ray ◽  
Ethylene Tetramerization ◽  
X Ray Crystallography ◽  
The Common ◽  
The One

CrCl3(thf)3 is a common starting material in the synthesis of organometallic and coordination compounds of Cr. Deposited as an irregular solid with no possibility of recrystallization, it is not a purity guaranteed chemical, causing problems in some cases. In this work, we disclose a well-defined form of the THF adduct of CrCl3 ([CrCl2(μ-Cl)(thf)2]2), a crystalline solid, that enables structure determination by X-ray crystallography. The EA data and XRD pattern of the bulk agreed with the revealed structure. Moreover, its preparation procedure is facile: evacuation of CrCl3·6H2O at 100 °C, treatment with 6 equivalents of Me3SiCl in a minimal amount of THF, and crystallization from CH2Cl2. The ethylene tetramerization catalyst [iPrN{P(C6H4-p-Si(nBu)3)2}2CrCl2]+[B(C6F5)4]− prepared using well-defined [CrCl2(μ-Cl)(thf)2]2 as a starting material exhibited a reliably high activity (6600 kg/g-Cr/h; 1-octene selectivity at 40 °C, 75%), while that of the one prepared using the impure CrCl3(thf)3 was inconsistent and relatively low (~3000 kg/g-Cr/h). By using well-defined [CrCl2(μ-Cl)(thf)2]2 as a Cr source, single crystals of [(CH3CN)4CrCl2]+[B(C6F5)4]− and [{Et(Cl)Al(N(iPr)2)2}Cr(μ-Cl)]2 were obtained, allowing structure determination by X-ray crystallography, which had been unsuccessful when the previously known CrCl3(thf)3 was used as the Cr source.

Structural studies on 6-ethoxytetrahydropyrylium cations; stereoelectronic control in the reactions of lactonium salts

1991 ◽  
Vol 69 (12) ◽  
pp. 2024-2032 ◽  
Author(s):  
Ronald F. Childs ◽  
Marianne D. Kostyk ◽  
Colin J. L. Lock ◽  
Mailivaganam Mahendran
Keyword(s):  
Nmr Spectra ◽  
Positive Charge ◽  
Nucleophilic Attack ◽  
Structural Studies ◽  
Narrow Line ◽  
Crystal Lattices ◽  
X Ray ◽  
X Ray Crystallography ◽  
Stereoelectronic Control ◽  
C Nmr

The structures of 6-ethoxy-2,3,4,5-tetrahydropyrylium, 1, 6-ethoxy-2-methyl-2,3,4,5-tetrahydropyrylium, 2, and 2-ethoxy-3,4,4a,5,6,7,8,8a-octahydro-1-benzopyrylium, 3, hexachloroantimonates have been determined by X-ray crystallography. In each case the tetrahydropyrylium rings exist in shallow half-chair conformations with the cationic centers C(6), C(5), O(1), and O(6) having a planar arrangement. The cations all have a Z conformation about the O(6)—C(7) bonds and it is shown that this conformation is also preferred in solution by comparison of narrow-line 13C NMR spectra in the solid state and solution. The O(1)—C(2) and O(6)—C(7) bond distances in 1–3 are significantly longer than those of comparable bonds in neutral esters. The length of the O(1)—C(2) bond is very dependent on substitution at C(2) suggesting a considerable fraction of the positive charge resides on this carbon as well as C(7). The closest cation/anion interactions present in the crystal lattices of these salts are between the chlorine atoms of the anion and the cationic center, C(6). These interactions provide information on the origin of the stereoselectivity observed in nucleophilic attack on these cations. The conformations, details of the C—O bonding, and closest contacts between cation and anion are discussed in terms of the concept of stereoelectronic control. Key words: 6-ethoxytetrahydropyrylium cations, lactonium salts, structure, X-ray, stereoelectronic control.

scholarly journals Quantum refinement with multiple conformations: application to the P-cluster in nitrogenase

2020 ◽  
Vol 76 (11) ◽  
pp. 1145-1156
Author(s):  
Lili Cao ◽  
Ulf Ryde
Keyword(s):  
Crystal Structures ◽  
Real Space ◽  
Scattering Data ◽  
Original Structure ◽  
X Ray ◽  
X Ray Crystallography ◽  
X Ray Scattering ◽  
Density Maps ◽  
Multiple Conformations ◽  
The One

X-ray crystallography is the main source of atomistic information on the structure of proteins. Normal crystal structures are obtained as a compromise between the X-ray scattering data and a set of empirical restraints that ensure chemically reasonable bond lengths and angles. However, such restraints are not always available or accurate for nonstandard parts of the structure, for example substrates, inhibitors and metal sites. The method of quantum refinement, in which these empirical restraints are replaced by quantum-mechanical (QM) calculations, has previously been suggested for small but interesting parts of the protein. Here, this approach is extended to allow for multiple conformations in the QM region by performing separate QM calculations for each conformation. This approach is shown to work properly and leads to improved structures in terms of electron-density maps and real-space difference density Z-scores. It is also shown that the quality of the structures can be gauged using QM strain energies. The approach, called ComQumX-2QM, is applied to the P-cluster in two different crystal structures of the enzyme nitrogenase, i.e. an Fe8S7Cys6 cluster, used for electron transfer. One structure is at a very high resolution (1.0 Å) and shows a mixture of two different oxidation states, the fully reduced PN state (Fe8 2+, 20%) and the doubly oxidized P2+ state (80%). In the original crystal structure the coordinates differed for only two iron ions, but here it is shown that the two states also show differences in other atoms of up to 0.7 Å. The second structure is at a more modest resolution, 2.1 Å, and was originally suggested to show only the one-electron oxidized state, P1+. Here, it is shown that it is rather a 50/50% mixture of the P1+ and P2+ states and that many of the Fe—Fe and Fe—S distances in the original structure were quite inaccurate (by up to 0.8 Å). This shows that the new ComQumX-2QM approach can be used to sort out what is actually seen in crystal structures with dual conformations and to give locally improved coordinates.

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