Harnessing Anionic Rearrangements on the Benzenoid Ring of Quinoline for the Synthesis of 6,6‘-Disubstituted 7,7‘-Dihydroxy-8,8‘-biquinolyls

2005 ◽  
Vol 70 (1) ◽  
pp. 373-376 ◽  
Author(s):  
Paul R. Blakemore ◽  
Colin Kilner ◽  
Selena D. Milicevic
Keyword(s):  
Benzenoid Ring

Synthesis of 5,7-dihydroxynaphthoquinone derivatives and their reactions with nucleophiles: Nitration of 2,3-dimethylnaphthalene and subsequent transformations

1976 ◽  
Vol 29 (10) ◽  
pp. 2247 ◽  
Author(s):  
HJ Banks ◽  
DW Cameron ◽  
MJ Crossley ◽  
EL Samuel
Keyword(s):  
Unusual Reaction ◽  
Nitro Derivatives ◽  
Reactions With Nucleophiles ◽  
Derivatives Of ◽  
Related Compounds ◽  
Benzenoid Ring

5,7-Dihydroxy-2,3-dimethyl-l,4-naphthoquinone (5) and related compounds have been synthesized. The quinone affords an accessible substrate for studying an unusual reaction with nucleophiles, which involves attack at the 8-position, i.e. at the benzenoid ring. An unsuccessful approach to (5) has led to tri- and tetra-nitro derivatives of 2,3-dimethylnaphthalene. Reduction of the former and subsequent conversions have given aminonaphthoquinone and perimidinone derivatives.

scholarly journals Effect of Trifluoromethyl Substitution on C-3 Position in 1H NMR of Quinolones / Coumarins

2016 ◽  
Vol 8 (3) ◽  
pp. 1707-1715
Author(s):  
Anjali Gupta ◽  
Rajinder K. Gupta
Keyword(s):  
Spectral Data ◽  
1H Nmr ◽  
Structural Assignment ◽  
Benzenoid Ring

The structural assignment of differently substituted quinolones / coumarins was reviewed using 1H NMR spectral data. In case of quinolones / coumarins, with varied substitutions at C-4 and different positions of the benzenoid ring, there is a great variation in the 1H NMR value of the proton only attached with C-3. It was observed that when different substitutions (methyl / amino / hydroxy / acetoxy / trifluoromethyl) were carried out at C-4 position, maximum deshielding with the proton attached with C-3 was observed with trifluoromethyl substitution. The observation is same even with the variation in different groups at the benzenoid ring. 

scholarly journals Design and properties of a fluorescent indicator of intracellular free Na+ concentration

1988 ◽  
Vol 250 (1) ◽  
pp. 227-232 ◽  
Author(s):  
G A Smith ◽  
T R Hesketh ◽  
J C Metcalfe
Keyword(s):  
Aqueous Solubility ◽  
Ratio Method ◽  
Isosbestic Point ◽  
Buffer Solution ◽  
Acetoxymethyl Ester ◽  
Apparent Dissociation Constant ◽  
Fluorescent Indicator ◽  
Carboxylate Groups ◽  
Reporter Group ◽  
Benzenoid Ring

We have recently described a cryptand structure, FCryp-1, with appropriate properties for an indicator of intracellular free Na+ concentration using the 19F-n.m.r. chemical shift of the incorporated 5FBAPTA [1,2-bis-(2-amino-5-fluorophenoxy)ethane-NNN‘N’-tetra-acetic acid] reporter group to measure the free cytosolic Na+ concentration [(Na+]i) [Smith, Morris, Hesketh and Metcalfe (1986) Biochim. Biophys. Acta 889, 82-83]. FCryp-1 carries four carboxylate groups to confer aqueous solubility and the indicator is membrane-permeant when the carboxyls are esterified with acetoxymethyl ester groups. Here we describe the synthesis of FCryp-2 to provide a fluorescent indicator of [Na+]i. FCryp-2 retains the parent tribenzo (2:2:1) cryptand structure of FCryp-1, in which the benzenoid ring at C-21 in FCryp-1 is replaced by an indole derivative which acts as the fluorophor in FCryp-2. With excitation at 340 nm, FCryp-2 gives an emission maximum at 460 nm in the absence of Na+ which shifts to 395 nm when FCryp-2 is saturated with Na+, with an isosbestic point at 455 nm. The apparent dissociation constant of FCryp-2 in a buffer solution of 100 mM-KCl/20 mM-KH2PO4/K2HPO4, pH 7.0, at 37 degrees C is 6.0 mM and the free Na+ concentration can be measured either from the calibrated fluorescence intensity at 395 nm, which increases 25-fold when Na+ is bound to FCryp-2, or from the ratio of fluorescence intensities at 395 nm and 455 nm. The measurement of free [Na+] by either method is unaffected by K+, Ca2+ or Mg2+ in the normal intracellular concentration ranges. Free [Na+] measurements by the ratio method are unaffected by pH from 6.6 to 7.6.

Structural characterization of p-benzosemiquinone radical in a solid state: the radical stabilization by a low-barrier hydrogen bond

2006 ◽  
Vol 62 (6) ◽  
pp. 1051-1060 ◽  
Author(s):  
Krešimir Molčanov ◽  
Biserka Kojić-Prodić ◽  
Mario Roboz
Keyword(s):  
Hydrogen Bond ◽  
Solid State ◽  
Variable Temperature ◽  
Organic Radical ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Packings ◽  
Dynamical Disorder ◽  
Benzenoid Ring

Semiquinone (p-benzosemiquinone), a transient organic radical, was detected in the solid state by EPR spectroscopy revealing four symmetrically equivalent protons. A variable-temperature X-ray diffraction analysis (293 and 90 K) and EPR data support a dynamical disorder of the proton. A low-barrier O—H···O hydrogen bond stabilizes the radical. The C—O bond length is 1.297 (4) Å, corresponding to a bond order of ca 1.5. The geometry of the radical implies an electron delocalization throughout the benzenoid ring. Two polymorphs of semiquinone, monoclinic and triclinic, were observed and their structures determined. Their crystal packings were compared with those of quinhydrone polymorphs.

Reactions of Perimidin-4-ones and -6-ones with amines

1977 ◽  
Vol 30 (9) ◽  
pp. 2063 ◽  
Author(s):  
DW Cameron ◽  
EL Samuel
Keyword(s):  
Double Bond ◽  
Room Temperature ◽  
Significant Degree ◽  
Secondary Amines ◽  
Nucleophilic Attack ◽  
Side Chain ◽  
Amino Compounds ◽  
Primary And Secondary Amines ◽  
Benzenoid Ring

π-Deficient perimidin-4- and -6-one systems reacted readily with primary and secondary amines at room temperature. Nucleophilic attack occurred not only at the enone double bond, but also at positions 7 and 9 on the benzenoid ring. Highly coloured mono-, di- or tri-aminated derivatives were thereby obtained. A significant degree of bond fixation was indicated. Side-chain amination of 9-methyl substituents was observed, analogous to processes encountered in quinone chemistry. On continued contact with amine the products were converted partly into 9-formyl derivatives and partly into 9-amino compounds.

Nucleophilic alkenes. VII. 1 : 2-Addition of 1,1 -dimethoxyethene to 1,4-naphthoquinones substituted in the benzenoid ring

1980 ◽  
Vol 33 (8) ◽  
pp. 1805 ◽  
Author(s):  
DW Cameron ◽  
GI Feutrill ◽  
AF Patti
Keyword(s):  
Substituent Effects ◽  
Isomeric Mixtures ◽  
Benzenoid Ring

Several 5-substituted 1,4-naphthoquinones have been treated with 1,1- dimethoxyethene to give isomeric mixtures of 1,3,5- and 1,3,8- trisubstituted anthraquinones. Similarly 6-substituted 1,4- naphthoquinonesgave mixtures of the 1,3,6- and 1,3,7-series. The course of these reactions has been correlated with substituent effects.

Tropone (cyclohepta-2,4,6-trienone) derivatives related to biphenylene. 5H-Benzo[3,4]cyclobuta[1,2]cyclohepten-5-one, 6H-Benzo[3,4]cyclobuta[1,2]cyclohepten-6-one and 7H-Benzo[3,4]cyclobuta[1,2]cyclohepten-7-one

1978 ◽  
Vol 31 (7) ◽  
pp. 1585 ◽  
Author(s):  
L Lombardo ◽  
RK McCulloch ◽  
D Wege
Keyword(s):  
Membered Ring ◽  
Crystalline Solid ◽  
Bond System ◽  
Synthetic Routes ◽  
Benzenoid Ring

Synthetic routes to 5H-benzo[3,4]cyclobuta[1,2]cyclohepten-5-one (6), 6H-benzo[3,4]cyclobuta-[1,2]cyclohepten-6-one (5) and 7H- benzo[3,4]cyclobuta[1,2]cyclohepten-7-one (7), which are analogues of biphenylene in which one benzenoid ring has been replaced by the cyclohepta-2,4,6-trienone (tropone) ring, have been investigated. The tropone (5) was obtained as a stable, crystalline solid and 1H n.m.r, evidence suggests that (5) has a more localized π-bond system in the seven-membered ring than tropone itself. The reactive tropone derivative (7) was generated in solution, and trapped as a 6πs+4πs cycloadduct with cyclopentadiene.

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