CYCLIC COMPOUNDS CONTAINING A CARBONYL GROUP; A MECHANISM FOR THE FORMATION OF PYRYLLIUM SALTS FROM 1,5-DIKETONES

1933 ◽  
Vol 9 (6) ◽  
pp. 574-582 ◽  
Author(s):  
C. F. H. Allen ◽  
H. R. Sallans
Keyword(s):  
Carbonyl Group ◽  
Methyl Ether ◽  
Ring Closure ◽  
Closed Ring ◽  
Second Mode ◽  
Ring Structures ◽  
Group A ◽  
Plausible Mechanism ◽  
Cyclic Compounds

In the presence of alkali, cyclohexanone and its homologues add to chalcones to form either semicyclic diketones or dicyclic keto-alcohols; the latter contain a carbonyl bridge, and the former can be converted into closed ring structures and dehydrated to form substances having a carbonyl bridge. In these dicyclic ketones the bridge is not removed by heating, in contrast to the behavior of certain other compounds having a similar ring system.A second mode of ring closure gives rise to pyryllium salts; the isolation of a methyl ether has made it possible to devise a plausible mechanism for this hitherto obscure reaction. Four varieties of salts are described, the perchlorates being obtained by a different procedure than that previously employed.

THE CONDENSATION OF CERTAIN γ-KETONIC ESTERS WITH AROMATIC ALDEHYDES

1932 ◽  
Vol 6 (6) ◽  
pp. 605-613 ◽  
Author(s):  
C. F. H. Allen ◽  
G. F. Frame
Keyword(s):  
Carbonyl Group ◽  
Aromatic Aldehydes ◽  
Sodium Methylate ◽  
Ring Closure ◽  
Aryl Group ◽  
Appropriate Treatment ◽  
Ketone Carbonyl ◽  
Branched Chain ◽  
Cyclic Compounds ◽  
Chloride Methyl

The condensation of methyl and ethyl α-phenyl-β-(para-substituted)benzoyl propionates with benzaldehyde and piperonal in the presence of sodium methylate, followed by acidification, has been found to produce cyclic compounds; the latter are shown to be lactols, six of which are described. The spontaneous ring closure is probably due to the highly branched chain. A mechanism for the reaction is proposed.On oxidation with chromic acid, α-diketones are formed; the latter contain the aryl group introduced as aldehyde. The lactols resemble triphenylcarbinol in several respects, forming a chloride, methyl ether, and acetate on appropriate treatment, all of which, on hydrolysis, regenerate the lactol. They also give colored solutions with concentrated sulphuric acid, from which the starting material is recovered on addition to water. From this work it is evident that in arylated γ-ketonic esters the hydrogen atom alpha to the ketone carbonyl group is more active in alkaline aldol condensations than the hydrogen in the alpha position to the carbalkoxy carbonyl group; the observation of others, that the conjugated system [Formula: see text] is more stable than [Formula: see text], has been confirmed.

scholarly journals Molecular mechanisms of substrate-controlled ring dynamics and substepping in a nucleic acid-dependent hexameric motor

2016 ◽  
Vol 113 (48) ◽  
pp. E7691-E7700 ◽  
Author(s):  
Nathan D. Thomsen ◽  
Michael R. Lawson ◽  
Lea B. Witkowsky ◽  
Song Qu ◽  
James M. Berger
Keyword(s):  
Conformational Changes ◽  
Molecular Mechanisms ◽  
Atp Hydrolysis ◽  
Ring Closure ◽  
Scattering Data ◽  
Rna Sequences ◽  
Cofactor Binding ◽  
Closed Ring ◽  
Ring Structures ◽  
Structural Methods

Ring-shaped hexameric helicases and translocases support essential DNA-, RNA-, and protein-dependent transactions in all cells and many viruses. How such systems coordinate ATPase activity between multiple subunits to power conformational changes that drive the engagement and movement of client substrates is a fundamental question. Using theEscherichia coliRho transcription termination factor as a model system, we have used solution and crystallographic structural methods to delineate the range of conformational changes that accompany distinct substrate and nucleotide cofactor binding events. Small-angle X-ray scattering data show that Rho preferentially adopts an open-ring state in solution and that RNA and ATP are both required to cooperatively promote ring closure. Multiple closed-ring structures with different RNA substrates and nucleotide occupancies capture distinct catalytic intermediates accessed during translocation. Our data reveal how RNA-induced ring closure templates a sequential ATP-hydrolysis mechanism, provide a molecular rationale for how the Rho ATPase domains distinguishes between distinct RNA sequences, and establish structural snapshots of substepping events in a hexameric helicase/translocase.

Lithiation of bridgehead positions in 3,6-bridged piperazine-2,5-diones

1982 ◽  
Vol 35 (11) ◽  
pp. 2289 ◽  
Author(s):  
FW Eastwood ◽  
D Gunawardana ◽  
GT Wernert
Keyword(s):  
Carbonyl Group ◽  
Methyl Iodide ◽  
Methyl Ether ◽  
Sodium Methoxide ◽  
Inductive Effect ◽  
Amide Nitrogen

2,5-Dimethyl-2,5 diazabicyclo[2,2,2]octane-3,6-dione can be lithiated at the 1,4 (bridgehead) positions with 2 equiv. of t-butyllithium at -78� and deuterated with D2O (Do, 11.2; Dl, 56.1 ; D2, 30.1%). With butyllithium and methyl iodide the 1,2,5-trimethyl and 1,2,4,5-tetramethyl derivatives are obtained. Treatment of dimethyl 2,6-diaminoheptanedioate dihydrochloride with sodium methoxide in boiling butanol gives 6,8-diazabicyclo[3,2,2]nonane-7,9-dione in 62% yield. N-Methylation of this compound yields 6,8-dimethyl-6,8-diazabicyclo[3,2,2]nonane-7,9-dione which can similarly be lithiated at the 1,5 (bridgehead) positions and deuterated with D2O (Do, 5.6; Dl, 70.8; D2, 23.6%). Lithiation with butyllithium and reaction with methyl iodide, benzyl iodide or bromomethyl methyl ether gives mono-and di-alkylated products at the 1,5-positions. The ability to lithiate the bridgehead positions in these compounds is attributed primarily to a combination of the inductive effect of the carbonyl group and dipole stabilization by the amide nitrogen.

One-Pot Access to 4-Aryl-2-arylacetoxynaphthalenes via Benz­annulation of Oxygenated Arylacetic Acids and Alkyl Aryl Ketones

Synthesis ◽  
2020 ◽  
Vol 52 (07) ◽  
pp. 1035-1046 ◽  
Author(s):  
Meng-Yang Chang ◽  
Shin-Mei Chen ◽  
Yu-Ting Hsiao
Keyword(s):  
Bond Formation ◽  
Trifluoroacetic Anhydride ◽  
Ring Closure ◽  
One Pot ◽  
Alkyl Aryl ◽  
Highly Effective ◽  
Aryl Ketones ◽  
Arylacetic Acids ◽  
Plausible Mechanism

Trifluoroacetic anhydride mediated one-pot intermolecular formal (4+2) benzannulation of oxygenated arylacetic acids with alkyl aryl ketones provides 4-aryl-2-arylacetoxynaphthalenes in moderate to good yields in the presence of H3PO4 in an open-vessel in a straightforward procedure. A plausible mechanism is proposed and discussed. This protocol provides a highly effective ring-closure via two carbon–carbon (C–C) and one carbon–oxygen (C–O) bond-formation events.

Hydration of the Carbonyl Group. A Theoretical Study of the Cooperative Mechanism

1995 ◽  
Vol 117 (15) ◽  
pp. 4240-4260 ◽  
Author(s):  
Saul Wolfe ◽  
Chan-Kyung Kim ◽  
Kiyull Yang ◽  
Noham Weinberg ◽  
Zheng Shi
Keyword(s):  
Carbonyl Group ◽  
Theoretical Study ◽  
Group A

INFRARED SPECTRA OF 2,6-DIMETHYL-4-PYRONE COMPLEXES

1961 ◽  
Vol 39 (6) ◽  
pp. 1184-1189 ◽  
Author(s):  
Denys Cook
Keyword(s):  
Complex Formation ◽  
Oxygen Atom ◽  
Carbonyl Group ◽  
Lewis Acid ◽  
Frequency Band ◽  
Infrared Spectra ◽  
Donor Site ◽  
Carbonyl Oxygen ◽  
Acid Strength ◽  
Group A

The infrared spectra of 2,6-dimethyl-4-pyrone in solution, and in complexes with HgCl2, ZnCl2, BF3, SbCl5, and HBr have been recorded. A band at 1639 cm−1 in the free pyrone moves to progressively lower frequencies in the complexes as the Lewis acid strength increases, identifying this band as the carbonyl stretching frequency and the donor site as the carbonyl group. A higher-frequency band, at 1678 cm−1 in the free pyrone, moves to lower frequency on complex formation, but to a much smaller extent, and is to be identified with a stretching mode of the ring. The site of protonation in 2,6-dimethyl-4-pyrone salts has been unequivocally shown to be the carbonyl oxygen atom.

scholarly journals Biologically controlled synthesis and assembly of magnetite nanoparticles

2015 ◽  
Vol 181 ◽  
pp. 71-83 ◽  
Author(s):  
Mathieu Bennet ◽  
Luca Bertinetti ◽  
Robert K. Neely ◽  
Andreas Schertel ◽  
André Körnig ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetite Nanoparticles ◽  
Super Resolution ◽  
Magnetotactic Bacteria ◽  
Biological Macromolecules ◽  
Free Standing ◽  
Magnetic Dipoles ◽  
Closed Ring ◽  
Major Player ◽  
Ring Structures

Magnetite nanoparticles have size- and shape-dependent magnetic properties. In addition, assemblies of magnetite nanoparticles forming one-dimensional nanostructures have magnetic properties distinct from zero-dimensional or non-organized materials due to strong uniaxial shape anisotropy. However, assemblies of free-standing magnetic nanoparticles tend to collapse and form closed-ring structures rather than chains in order to minimize their energy. Magnetotactic bacteria, ubiquitous microorganisms, have the capability to mineralize magnetite nanoparticles, the so-called magnetosomes, and to direct their assembly in stable chainsviabiological macromolecules. In this contribution, the synthesis and assembly of biological magnetite to obtain functional magnetic dipoles in magnetotactic bacteria are presented, with a focus on the assembly. We present tomographic reconstructions based on cryo-FIB sectioning and SEM imaging of a magnetotactic bacterium to exemplify that the magnetosome chain is indeed a paradigm of a 1D magnetic nanostructure, based on the assembly of several individual particles. We show that the biological forces are a major player in the formation of the magnetosome chain. Finally, we demonstrate by super resolution fluorescence microscopy that MamK, a protein of the actin family necessary to form the chain backbone in the bacteria, forms a bundle of filaments that are not only found in the vicinity of the magnetosome chain but are widespread within the cytoplasm, illustrating the dynamic localization of the protein within the cells. These very simple microorganisms have thus much to teach us with regards to controlling the design of functional 1D magnetic nanoassembly.

STUDIES ON REACTIONS RELATING TO CARBOHYDRATES AND POLYSACCHARIDES. XXVII. SYNTHESIS AND STRUCTURE OF TRICHLOROETHYLIDENE GLYCEROL

1930 ◽  
Vol 2 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Harold Hibbert ◽  
J. G. Morazain ◽  
A. Paquet
Keyword(s):  
Sulphuric Acid ◽  
Methyl Ether ◽  
Ring Closure ◽  
Cyclic Acetal ◽  
Satisfactory Explanation ◽  
Carbonyl Derivative ◽  
Cyclic Acetals ◽  
Polyhydroxy Compounds

A discussion is given as to the nature of the factors involved in the mechanism of the formation of cyclic acetals and ketals from carbonyl and polyhydroxy derivatives. It is shown that in the two reactions involved, namely, the primary formation of a half-acetal, followed by removal of water and ring-closure, the polarity of the carbonyl derivative plays a very important rôle. Chloral combines with polyhydroxy compounds to give exceptionally stable half-acetals, which can be converted into the cyclic derivatives by the use of strong dehydrating agents.In contrast with the behavior of other aldehydes it is found that the condensation of chloral with glycerol yields only one ring compound, namely the five-membered derivative. No satisfactory explanation of this can, as yet, be given.The identity of the trichloroethylidene glycerol obtained by the condensation of glycerol and chloral under the influence of concentrated sulphuric acid has been established as a five-membered cyclic acetal by a comparison of the properties of its methyl ether with those of trichloroethylidene glycerol α-methyl ether prepared from glycerol α-methyl ether.

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