Critical dependence of the stability of an overcrowded benzylic carbocation on the aromatic ring substituent. Substituent and solvent effects on the ring opening of 1-aryl-substituted epoxides. 1-(p-Methoxyphenyl)-2,2-dimethyl-7-oxabicyclo[4.1.0]heptane

1974 ◽  
Vol 39 (7) ◽  
pp. 874-877 ◽  
Author(s):  
Aldo Balsamo ◽  
Paolo Crotti ◽  
Bruno Macchia ◽  
Franco Macchia
Keyword(s):  
Aromatic Ring ◽  
Solvent Effects ◽  
Ring Opening ◽  
Ring Substituent ◽  
The Stability

scholarly journals Theoretical Study on the Photo-Oxidation and Photoreduction of an Azetidine Derivative as a Model of DNA Repair

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2911
Author(s):  
Miriam Navarrete-Miguel ◽  
Antonio Francés-Monerris ◽  
Miguel A. Miranda ◽  
Virginie Lhiaubet-Vallet ◽  
Daniel Roca-Sanjuán
Keyword(s):  
Electron Transfer ◽  
Energy Barrier ◽  
Ring Opening ◽  
Dna Lesions ◽  
Barrier Heights ◽  
Dna Lesion ◽  
Electron Reduction ◽  
The Stability ◽  
Electron Transfer Processes

Photocycloreversion plays a central role in the study of the repair of DNA lesions, reverting them into the original pyrimidine nucleobases. Particularly, among the proposed mechanisms for the repair of DNA (6-4) photoproducts by photolyases, it has been suggested that it takes place through an intermediate characterized by a four-membered heterocyclic oxetane or azetidine ring, whose opening requires the reduction of the fused nucleobases. The specific role of this electron transfer step and its impact on the ring opening energetics remain to be understood. These processes are studied herein by means of quantum-chemical calculations on the two azetidine stereoisomers obtained from photocycloaddition between 6-azauracil and cyclohexene. First, we analyze the efficiency of the electron-transfer processes by computing the redox properties of the azetidine isomers as well as those of a series of aromatic photosensitizers acting as photoreductants and photo-oxidants. We find certain stereodifferentiation favoring oxidation of the cis-isomer, in agreement with previous experimental data. Second, we determine the reaction profiles of the ring-opening mechanism of the cationic, neutral, and anionic systems and assess their feasibility based on their energy barrier heights and the stability of the reactants and products. Results show that oxidation largely decreases the ring-opening energy barrier for both stereoisomers, even though the process is forecast as too slow to be competitive. Conversely, one-electron reduction dramatically facilitates the ring opening of the azetidine heterocycle. Considering the overall quantum-chemistry findings, N,N-dimethylaniline is proposed as an efficient photosensitizer to trigger the photoinduced cycloreversion of the DNA lesion model.

Effect of the support acidity on the aromatic ring-opening of pyrolysis gasoline over Pt/HZSM-5 catalysts

2009 ◽  
Vol 143 (1-2) ◽  
pp. 115-119 ◽  
Author(s):  
Pedro Castaño ◽  
Alazne Gutiérrez ◽  
Inés Villanueva ◽  
Barbara Pawelec ◽  
Javier Bilbao ◽  
...  
Keyword(s):  
Aromatic Ring ◽  
Ring Opening ◽  
Pyrolysis Gasoline ◽  
Effect Of The Support

scholarly journals Solvent Effects on Stereo and Regioselectivities of Ring-opening Reaction of Epoxide with Aluminum Chloride

1976 ◽  
Vol 49 (4) ◽  
pp. 1063-1071 ◽  
Author(s):  
Masashi Inoue ◽  
Toshio Sugita ◽  
Yoshiaki Kiso ◽  
Katsuhiko Ichikawa
Keyword(s):  
Solvent Effects ◽  
Aluminum Chloride ◽  
Ring Opening ◽  
Ring Opening Reaction

Linear and cross-linked mixed conducting polycarbazoles for electrochromic devices

2001 ◽  
Vol 708 ◽  
Author(s):  
François Tran-Van ◽  
Cédric Vancaeyzeele ◽  
Thierry Henri ◽  
Juozas V. Grazulevicius ◽  
Claude Chevrot
Keyword(s):  
Mechanical Properties ◽  
Ring Opening ◽  
Acidic Medium ◽  
Solid Electrolytes ◽  
Oxidation Potential ◽  
Electrochromic Device ◽  
Electrochromic Devices ◽  
Acid Catalyzed ◽  
The Stability ◽  
Cationic Ring Opening Polymerization

ABSTRACTA carbazole N-substituted by an oxyethylene group was polymerized using oxidative electro-polymerization. Due to the hydrophilic properties of the oligooxyethylene substituent, this monomer can be electropolymerized in aqueous solution. An acidic medium is particularly appropriate in order to decrease the oxidation potential of the monomer and to obtain films mainly composed of oligomers as revealed by SEC analysis. More particularly interesting is the stability of such material during polarization. In acidic medium 1.25 mol.L-1 HClO4, 95% of the charge density was maintained after polarization for 7000 cycles which shows the good electrochemical stability of this material compared to other polycarbazoles. Moreover, films are electroactive in aqueous electrolytes and would be well-compatible with polyethylene-oxide solid electrolytes.In order to increase the mechanical properties of the film, we have also electropolymerized an oligomer with pendant carbazole groups obtained by acid catalyzed cationic ring opening polymerization of [N(2,3-epoxypropyl)carbazole] which leads to a new dicarbazyl cross-linked polymer with cations solvating oxyethylene segments. Due to their tridimensional structure, the mechanical strength of these films is superior to that of a linear polycarbazole film. However, their electroactivity in aqueous electrolyte is poor. So, the electropolymerization of a mixture of both monomers ensures good mechanical properties and compatibility with hydrophilic electrolyte in view to prepare an electrochromic device.

Facile Synthesis of Thiols and Sulfides

1975 ◽  
Vol 53 (10) ◽  
pp. 1480-1483 ◽  
Author(s):  
Jean-Rock Brindle ◽  
Jean-Louis Liard
Keyword(s):  
Aromatic Ring ◽  
Sodium Borohydride ◽  
Facile Synthesis ◽  
Experimental Conditions ◽  
The Stability ◽  
High Yields

Sulfurated sodium borohydride reacts with benzylic halides to give high yields of α-toluenethiol or benzylic polysulfldes depending upon the experimental conditions and the mode of hydrolysis.Aliphatic halides and dibenzylic halides react in the same manner as benzylic halides for a given experimental condition whereas benzylic halides substituted with other groups can be totally or partially reduced depending on the stability of the substituent towards NaBH2S3.Halogens directly attached on the aromatic ring do not react with NaBH2S3.

ChemInform Abstract: Aromatic Ring Opening of Fused Thiophenes via Organolithium Addition to Sulfur.

ChemInform ◽  
2010 ◽  
Vol 29 (28) ◽  
pp. no-no
Author(s):  
B. HILL ◽  
M. DE VLEESCHAUWER ◽  
K. HOUDE ◽  
M. BELLEY
Keyword(s):  
Aromatic Ring ◽  
Ring Opening ◽  
Fused Thiophenes
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