scholarly journals Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

2020 ◽  
Vol 16 ◽  
pp. 904-916
Author(s):  
Phil M Pithan ◽  
Sören Steup ◽  
Heiko Ihmels
Keyword(s):  
Ring Opening ◽  
Oxidation Reaction ◽  
Mass Spectrometric ◽  
Ring Closure ◽  
Fluorimetric Detection ◽  
Broad Absorption ◽  
Broad Absorption Band ◽  
Ring Opening Reaction ◽  
Screening Assays ◽  
Photochemical Properties

Two new spiroindolinonaphthoxazine derivatives with an electron-accepting styrylquinolizinium or styrylcoralyne unit, respectively, were synthesized, and the influence of such an arylvinyl substituent on the chemical and photochemical properties of the compounds was investigated. Specifically, these spirooxazines turned out to be resistant towards the photoinduced merocyanine formation, and the irradiation with light mainly led to photodegradation of the substrates. However, it was shown by colorimetric and fluorimetric screening assays as well as by detailed NMR spectroscopic and mass spectrometric studies that the addition of particular metal ions (Cu2+, Fe3+, and to a certain extent Hg2+) initially induced a ring-opening reaction that was irreversibly followed by a fast ring closure–deprotonation–oxidation sequence to give styryl-substituted naphthoxazole derivatives as the products quantitatively. For the quinolizinium-substituted spirooxazine derivative, the formation of the respective oxidation product caused the development of a broad absorption band between 425 nm and 500 nm and a new emission band at λfl = 628 nm, so that it may be employed as a selective chemosensor or chemodosimeter for the colorimetric and fluorimetric detection of Cu2+ and Fe3+.

First Total Synthesis of a Fluorinated Calystegin

2010 ◽  
Vol 65 (4) ◽  
pp. 445-451 ◽  
Author(s):  
René Csuk ◽  
Erik Prell ◽  
Stefan Reißmann ◽  
Claudia Korb
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Competitive Inhibitor ◽  
Ring Closure ◽  
Target Compound ◽  
Metathesis Reaction ◽  
Grubbs Catalyst ◽  
Ring Opening Reaction ◽  
Ultrasound Assisted ◽  
Key Steps

A straightforward chiral pool synthesis for the first fluorinated calystegin is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. The target compound is a selective and competitive inhibitor for a β -glycosidase.

Thermal intramolecular reactions of Δ1-1,2,4-triazolines with extended exocyclic unsaturation

1988 ◽  
Vol 66 (3) ◽  
pp. 385-390 ◽  
Author(s):  
Adrian L. Schwan ◽  
John Warkentin
Keyword(s):  
Ring Opening ◽  
Hydrolysis Product ◽  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Closure ◽  
Experimental Results ◽  
First Order ◽  
Ring Opening Reaction ◽  
Intramolecular Reactions

Fumaratotriazoline (1) and amidotriazoline (3) undergo thermal first-order transformations in solution at 65 °C. The former affords the isomeric pyrrole 5 and its hydrolysis product 6. A mechanism involving opening of the initial five-membered ring to form 8, followed by closure to a new five-membered ring (9), is proposed. Amidotriazoline (3) loses N2 on heating to form 19. The experimental results are best accommodated in terms of a novel mechanism involving an electrocyclic ring closure, a [3 + 2] cycloreversion to form an ylide, a sigmatropic rearrangement of the ylide, and, finally, an electrocyclic ring-opening reaction.

scholarly journals Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

2020 ◽  
Author(s):  
Kazuyuki Sato ◽  
Akira Kawasaki ◽  
Yukiko Karuo ◽  
Atsushi Tarui ◽  
Kentaro Kawai ◽  
...  
Keyword(s):  
Emission Intensity ◽  
Ring Opening ◽  
Fluorine Atom ◽  
Emission Property ◽  
Synthetic Methods ◽  
Fluorescent Intensity ◽  
Aggregation Induced Emission ◽  
Ring Opening Reaction ◽  
Photochemical Properties ◽  
Fluorescent Molecules

Fluorescent molecules based on a fluorinated isoxazole scaffold were provided for the synthetic methods and their photochemical properties.  Simple 3,5-diarylisoxazoles led to increasing the fluorescent intensity and exhibited a redshift in the emission intensity by introducing a fluorine atom.  α-Fluorinated boron ketoiminates (F-BKIs) derived from a ring opening reaction of 4-fluoroisoxazoles were also synthesized and exhibited a highly fluorescent luminescence as a new aggregation-induced emission (AIE) fluorophore.

Intermediates from ring-opening reactions. Reactions of 2-chloro-5-nitropyridine and 2-chloro-3-nitropyridine with deuteroxide ion in selected solvents

1984 ◽  
Vol 62 (6) ◽  
pp. 1120-1123 ◽  
Author(s):  
John D. Reinheimer ◽  
Nicolas Sourbatis ◽  
Robert L. Lavallee ◽  
Douglas Goodwin ◽  
George L. Gould
Keyword(s):  
Ring Opening ◽  
Pyridine Ring ◽  
Ring Closure ◽  
Polar Solvents ◽  
Open Chain ◽  
Decomposition Products ◽  
Aqueous Sodium ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Kinetics Of

Open chain intermediates from the ring-opening reaction of aqueous sodium deuteroxide (2 mol) with 2-chloro-5-nitropyridine (1 mol) and 2-chloro-3-nitropyridine (1 mol) were isolated. These intermediates were purified, analyzed for elemental composition, and characterized by various spectrophotometric techniques. The intermediate formed from 2-chloro-5-nitropyridine and two equivalents of deuteroxide ion reacts with additional deuteroxide in D2O in various polar solvents to reclose the pyridine ring. The kinetics of the ring closure reaction are reported and are supplemented with observations of salt and solvent effects upon the rate of closure. In addition, a mechanism for the ring closure is presented. The intermediate formed from 2-chloro-3-nitropyridine did not undergo a similar ring closure when reacted with additional deuteroxide, but instead formed various decomposition products. A reason for the failure of this ring closure is suggested.

scholarly journals Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

2020 ◽  
Vol 16 ◽  
pp. 1411-1417 ◽  
Author(s):  
Kazuyuki Sato ◽  
Akira Kawasaki ◽  
Yukiko Karuo ◽  
Atsushi Tarui ◽  
Kentaro Kawai ◽  
...  
Keyword(s):  
Fluorescence Intensity ◽  
Emission Intensity ◽  
Ring Opening ◽  
Emission Property ◽  
Aggregation Induced Emission ◽  
Ring Opening Reaction ◽  
Photochemical Properties ◽  
Fluorescent Molecules

Fluorescent molecules based on a fluorinated isoxazole scaffold were synthesized and investigated for their photochemical properties. The introduction of a fluorine substituent into 3,5-diarylisoxazoles led to an increase of fluorescence intensity and exhibited a redshift in the emission intensity. α-Fluorinated boron ketoiminates (F-BKIs) were also synthesized via a ring-opening reaction of 4-fluoroisoxazoles and exhibited highly fluorescent luminescence and aggregation-induced emission (AIE), showing promise as a new fluorophore.

scholarly journals REACTION OF 2-HETARYL-2-(DIHYDROFURAN-2(3H)-ILIDEN)ACETONITRILES WITH AROMATIC AMINES

2020 ◽  
pp. 47-51
Author(s):  
R. Shemehen ◽  
O. Khilya ◽  
Yu. Volovenko
Keyword(s):  
Aromatic Amines ◽  
Ring Opening ◽  
Catalytic Amount ◽  
Building Blocks ◽  
Heterocyclic Ring ◽  
Ring Closure ◽  
Reaction Conditions ◽  
Ring Opening Reaction ◽  
Ring Transformations ◽  
High Yields

This article reports on the reaction of 2-hetaryl-2-(furanyl-2-ylidene)acetonitriles with aromatic amines as N-nucleophiles. 2-Hetaryl-2-(furanyl-2-ylidene)acetonitriles represent versatile building blocks in syntheses of ω-(N-aryl)alkyl substituted heterocycles due to the presence of 1,3-bielectrophilic acrylonitrile fragment functionalized with unsaturated heterocyclic ring and nucleophilic azaheterocyclic moiety. The carbonyl group masked within the N-arylpyrrolidinylidene fragment which undergoes a ring opening through the reaction with nucleophiles. So, a method for the synthesis of 2-hetaryl-6-hydroxy-3-(arylamino)hex-2-enenitriles and 2-hetaryl-2-(N-arylpyrrolidin-2-ylidene)acetonitriles has been developed by us. The proposed scheme is based on the available reagents using. As a result of Michael addition, the aromatic amines to 2-hetaryl-2-(furanyl-2-ylidene)acetonitriles followed by ring transformations has formed two types of products, depending on the reaction conditions. The reaction of substituted furanylylideneacetonitriles with aromatic amines proceeds in good to high yields affording the corresponding 3-(arylamino)hex-2-enenitriles and 2-(N-arylpyrrolidin-2-ylidene)acetonitriles derivatives. The stereochemistry of the ring-opening reaction follows the rules of a classical SN2 mechanism. The resulting linear products can be cyclized to 2-hetaryl-2-(furanyl-2-ylidene)acetonitriles in high yields by treatment with the catalytic amount of acid or the equimolar amount of aromatic amines. Under these conditions 2-hetaryl-6-hydroxy-3-(arylamino)hex-2-enenitriles arising from reaction gives the ring closure. Since both ring-opening and cyclisation occur with fixed stereochemistry the reaction appears a valuable modification to the preparation of acetonitriles derivatives.

Synthesis and Self-assembly of Amphiphilic Hetero-arm Molecular Brushes

2011 ◽  
Vol 64 (8) ◽  
pp. 1100 ◽  
Author(s):  
Waled Hadasha ◽  
Mpho Mothunya ◽  
Niels Akeroyd ◽  
Bert Klumperman
Keyword(s):  
Self Assembly ◽  
Ring Opening ◽  
Alkyl Chain ◽  
Ring Closure ◽  
Molecular Brushes ◽  
Alkyl Amines ◽  
Ring Opening Reaction ◽  
Grafting From ◽  
Chain Lengths

We report the synthesis of amphiphilic hetero-arm molecular brushes (AMBs), which were prepared by a combination of ‘grafting from’ and ‘grafting onto’ methodologies. First, styrene-terminated polyethylene glycol macromonomer (VB-PEG12, ∼666 g mol–1) was copolymerized with maleic anhydride (MAnh) to yield a polymer containing hydrophilic PEG chains and reactive (MAnh) groups. Subsequently, the reactive MAnh units in the obtained polymer were modified via a ring-opening reaction using primary alkyl amines, with different alkyl chain lengths, as the nucleophile. In situ ring closure yielded the styrene–maleimide-based AMB. The amphiphilic character of the AMBs was used for their self-assembly in different solvents. The effect of the ratio in hydrophilic to hydrophobic graft length on the morphology of the assemblies was studied using scanning electron microscopy.

First Total Synthesis of 3-Epi-calystegin B2

2011 ◽  
Vol 66 (3) ◽  
pp. 317-323
Author(s):  
René Csuk ◽  
Stefan Reißmann ◽  
Ralph Kluge ◽  
Dieter Ströhl ◽  
Claudia Korb
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Tight Binding ◽  
Ring Closure ◽  
Hydroxyl Group ◽  
Target Compound ◽  
Metathesis Reaction ◽  
Ring Opening Reaction ◽  
Ultrasound Assisted ◽  
Key Steps

A straightforward chiral pool synthesis for a non-natural calystegin, 3-epi-B2, is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. Compared to calystegin B2, the target compound is no longer an inhibitor for a β -glycosidase hence proving that an equatorial hydroxyl group at position C-3 is necessary for a tight binding of calystegins into the active site of β -glycosidases.

On the Conrotatory Ring Opening of 3-Carbomethoxycyclobutene Vis-À-Vis 3-Carbomethoxy-1,2-Benzocyclobutene and the Predominant Inward Opening of 3-Dimethylaminocarbonyl-1,2-Benzocyclobutene

2018 ◽  
Author(s):  
Veejendra Yadav ◽  
Dasari L V K Prasad ◽  
Arpita Yadav ◽  
Maddali L N Rao
Keyword(s):  
Transition State ◽  
Ring Opening ◽  
Electron Process ◽  
Ring Opening Reaction ◽  
Stable Species ◽  
Electron Event

<p>The torquoselectivity of conrotatory ring opening of 3-carbomethoxycyclobutene is controlled by p<sub>C1C2</sub>→s*<sub>C3C4</sub> and s<sub>C3C4</sub>→p*<sub>CO</sub> interactions in the transition state in a 4-electron process as opposed to only s<sub>C3C4</sub>→p*<sub>CO</sub> interaction in an apparently 8-electron event in 3-carbomethoxy-1,2-benzocyclobutene. The ring opening of 3-carbomethoxy-1,2-benzocyclobutene is sufficiently endothermic. We therefore argue that the reverse ring closing reaction is faster than the forward ring opening reaction and, thus, it establishes an equilibrium between the two and subsequently allows formation of the more stable species <i>via</i> outward ring opening reaction. Application of this argument to 3-dimethylaminocarbonyl-1,2-benzocyclobutene explains the predominantly observed inward opening.</p>

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