Rearrangements of Cyclobutenones. Electrocyclic Ring Closure and Thermal Ring Expansions of 3-Allenyl- and 3-Alkynyl-2-dienyl-4,4- dimethoxycyclobutenones

2002 ◽  
Vol 67 (4) ◽  
pp. 1388-1391 ◽  
Author(s):  
Antonio R. Hergueta ◽  
Harold W. Moore
Keyword(s):  
Ring Closure ◽  
Ring Expansions

Ring Closure Matrix

2015 ◽  
Vol 19 (3) ◽  
pp. 274-281
Author(s):  
Milan Randic ◽  
Marjana Novic ◽  
Dejan Plavsic
Keyword(s):  
Ring Closure

A new heterocyclic ring closure in ferricyanide oxidation of 2,4,6-triphenylpyridinium salts

1983 ◽  
Vol 48 (11) ◽  
pp. 3307-3314 ◽  
Author(s):  
Petr Nesvadba ◽  
Petr Štrop ◽  
Josef Kuthan
Keyword(s):  
Alkaline Solution ◽  
Heterocyclic Ring ◽  
Potassium Ferricyanide ◽  
Probable Mechanism ◽  
Ring Closure ◽  
Pyridinium Salts ◽  
Mechanism Of Formation ◽  
Pyrrole Derivatives ◽  
Quaternary Pyridinium Salts ◽  
Heterocyclic Derivatives

The quaternary pyridinium salts Ia-Ic react with alkaline solution of potassium ferricyanide to give the condensed heterocyclic derivatives IIIa, b, IV, whereas the salts Id-If give the pyrrole derivatives IIa-IIc under the same conditions. The diaza heterocycle IIIa reacts with methyl iodide to give methoiodide V, whereas by action of bromine it produces two monobromo derivatives VIa, b. The pyrrole derivatives IIa, b give monobromo derivatives IId, e on bromination. A probable mechanism of formation of the heterocyclic derivatives is discussed.

XXI.—The Synthesis of Some Methyl- and Dimethylfluoranthenes

1972 ◽  
Vol 69 (4) ◽  
pp. 281-286
Author(s):  
H. F. Andrew ◽  
Neil Campbell ◽  
E. M. Swan ◽  
N. H. Wilson
Keyword(s):  
Benzene Ring ◽  
Propionic Acid ◽  
Hydrofluoric Acid ◽  
Phenyl Ring ◽  
Ring Closure ◽  
Methyl Group ◽  
Image Position

3-Methylfluorene-9-propionic acid (1) with hydrofluoric acid undergoes ring-closure on the substituted ring to give 1,2,3,10b-tetrahydro-5-methylfluoranthen-3-one (II).Wolff-Kishner reduction of the ketone yielded l,2,3,10b-tetrahydro-5-methylfluoranthene which on dehydrogenation gave 2-methylfluoranthene (III, R=H) identical with a sample prepared according to the method of Tucker (1952) and differing from 8-methylfluoranthene. This proved that ring-closure of (I) had occurred as expected on the methyl-bearing benzene ring. In this instance ring-closure occurs in the position meta to the methyl group and is reminiscent of the similar ring-closure of 2-phenyl-2-p-tolylpropionic acid to give 6-methyl-3-phenylindanone (Pfeiffer and Roos 1941). It thus provided a further example of the limitations of von Braun's statement that Friedel-Crafts ring-closure occurs much less readily at the position meta to a methyl group than on a phenyl ring (von Braun, Manz and Reinsch 1928).

scholarly journals Structures of Rhodopseudomonas palustris RC-LH1 complexes with open or closed quinone channels

2021 ◽  
Vol 7 (3) ◽  
pp. eabe2631
Author(s):  
David J. K. Swainsbury ◽  
Pu Qian ◽  
Philip J. Jackson ◽  
Kaitlyn M. Faries ◽  
Dariusz M. Niedzwiedzki ◽  
...  
Keyword(s):  
Binding Sites ◽  
Rhodopseudomonas Palustris ◽  
Ring Closure ◽  
Light Harvesting Complex ◽  
The Core ◽  
Quinone Binding ◽  
Cryo Electron Microscopy ◽  
Unique Protein ◽  
Center Light ◽  
Resolution Structure

The reaction-center light-harvesting complex 1 (RC-LH1) is the core photosynthetic component in purple phototrophic bacteria. We present two cryo–electron microscopy structures of RC-LH1 complexes from Rhodopseudomonas palustris. A 2.65-Å resolution structure of the RC-LH114-W complex consists of an open 14-subunit LH1 ring surrounding the RC interrupted by protein-W, whereas the complex without protein-W at 2.80-Å resolution comprises an RC completely encircled by a closed, 16-subunit LH1 ring. Comparison of these structures provides insights into quinone dynamics within RC-LH1 complexes, including a previously unidentified conformational change upon quinone binding at the RC QB site, and the locations of accessory quinone binding sites that aid their delivery to the RC. The structurally unique protein-W prevents LH1 ring closure, creating a channel for accelerated quinone/quinol exchange.

Spin-forbidden heavy-atom tunneling in the ring-closure of triplet cyclopentane-1,3-diyl

2021 ◽  
Author(s):  
Luís P. Viegas ◽  
Cláudio Manaia Nunes ◽  
Rui Fausto
Keyword(s):  
Heavy Atom ◽  
Ring Closure ◽  
Quantum Mechanical ◽  
Quantum Mechanical Tunneling

In 1975, Buchwalter and Closs reported one of the first examples of heavy-atom quantum mechanical tunneling (QMT) by studying the ring closure of triplet cyclopentane-1,3-diyl to singlet bicyclo[2.1.0]pentane in cryogenic...

β-Amino acid facilitates macrocyclic ring closure in a combinatorial library

1999 ◽  
Vol 40 (44) ◽  
pp. 7757-7760 ◽  
Author(s):  
Elizabeth A. Jefferson ◽  
Eric E. Swayze
Keyword(s):  
Amino Acid ◽  
Combinatorial Library ◽  
Ring Closure ◽  
Macrocyclic Ring
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