Search results for "Cyano"
showing 10 items of 1058 documents
Cycloaddition reactions of 1-tert-butyl-4-vinylpyrazole
1989
1-tert-Butyl-4-vinylpyrazole1 a reacts with dimethyl acetylenedicarboxylate (DMAD), methyl propiolate (MP) and N-phenylmaleimide (NPMI) affording the indazole derivatives2,3, and5 as a result of a Diels-Alder ([4 + 2]) cycloaddition. With diethylazodicarboxylate (DEAZD), tetracyanoethylene (TCNE) and 4-phenyl-1,2,4-triazole-3,5-dione (PTAD) the reaction takes place exclusively through the olefinic substituent and the adducts6,7, and9 were isolated. The alkenylpyrazoles1 b–d reacted withDMAD and N-phenylmaleimide to give polymers.
ChemInform Abstract: Cycloaddition Reactions of 1-tert.-Butyl-4-vinylpyrazole.
1990
1-tert-Butyl-4-vinylpyrazole1 a reacts with dimethyl acetylenedicarboxylate (DMAD), methyl propiolate (MP) and N-phenylmaleimide (NPMI) affording the indazole derivatives2,3, and5 as a result of a Diels-Alder ([4 + 2]) cycloaddition. With diethylazodicarboxylate (DEAZD), tetracyanoethylene (TCNE) and 4-phenyl-1,2,4-triazole-3,5-dione (PTAD) the reaction takes place exclusively through the olefinic substituent and the adducts6,7, and9 were isolated. The alkenylpyrazoles1 b–d reacted withDMAD and N-phenylmaleimide to give polymers.
ChemInform Abstract: Diels-Alder Reactions of Methyl- and π-Acceptor-Substituted 2- Vinylindoles with Dimethyl Acetylenedicarboxylate and Tetracyanoe…
2010
The Diels-Alder reactions of the 2-vinylindoles 1a-1d, which are now readily accessible, with dimethyl acetylenedicarboxylate and tetracyanoethylene give rise to the novel 1,2-dihydro- and 1,2,3,4-tetrahydrocarbazoles 2, 4, and 5 as well as the fully aromatized carbazoles 3. With regard to the product spectrum, the mechanistic rationale comprises a Diels-Alder step, formal 1,3-hydrogen shift, ene reaction, and dehydrogenation. Conformational aspects of the 1,2-dihydrocarbazoles 2b and 2c are also discussed.
Diels-alder reactions of methyl- and π-acceptor-substituted 2-vinylindoles with dimethyl acetylenedicarboxylate and tetracyanoethylene: Novel functio…
1991
The Diels-Alder reactions of the 2-vinylindoles 1a-1d, which are now readily accessible, with dimethyl acetylenedicarboxylate and tetracyanoethylene give rise to the novel 1,2-dihydro- and 1,2,3,4-tetrahydrocarbazoles 2, 4, and 5 as well as the fully aromatized carbazoles 3. With regard to the product spectrum, the mechanistic rationale comprises a Diels-Alder step, formal 1,3-hydrogen shift, ene reaction, and dehydrogenation. Conformational aspects of the 1,2-dihydrocarbazoles 2b and 2c are also discussed.
Cyanocobalamin Ultraflexible Lipid Vesicles: Characterization and In Vitro Evaluation of Drug-Skin Depth Profiles
2021
Atopic dermatitis (AD) and psoriasis are the most common chronic inflammatory skin disorders, which importantly affect the quality of life of patients who suffer them. Among other causes, nitric oxide has been reported as part of the triggering factors in the pathogenesis of both conditions. Cyanocobalamin (vitamin B12) has shown efficacy as a nitric oxide scavenger and some clinical trials have given positive outcomes in its use for treating skin pathologies. Passive skin diffusion is possible only for drugs with low molecular weights and intermediate lipophilicity. Unfortunately, the molecular weight and hydrophilicity of vitamin B12 do not predict its effective diffusion through the skin…
A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins
2018
Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The Europea…
On the nature of organic electron density transfer complexes within molecular electron density theory.
2019
The structural features of a series of organic molecular complexes formed between the strong electrophilic tetracyanoethylene and twelve benzene derivatives with increased nucleophilic character, herein called Electron Density Transfer Complexes (EDTCs), have been studied using Molecular Electron Density Theory. The favourable nucleophilic/electrophilic interactions, which favour the global electron density transfer (GEDT) towards the electrophile, are responsible for the formation of these species. Molecular complexes presenting a GEDT above 0.05e are classified as EDTCs. Analysis of the Parr functions of the separated reagents and the topological analysis of the electron density of the ED…
How does the global electron density transfer diminish activation energies in polar cycloaddition reactions? A Molecular Electron Density Theory study
2017
Abstract The key role of the Global Electron Density Transfer (GEDT) in polar cycloaddition reactions is analysed within the Molecular Electron Density Theory (MEDT) using Density Functional Theory (DFT) calculations at the MPWB1K/6-311G(d) computational level. A comparative MEDT study of the non-polar Diels-Alder reaction between cyclopentadiene (Cp) and ethylene and the polar Diels-Alder reaction between Cp and tetracyanoethylene makes it possible to establish that the GEDT taking place in the direction of the transition state structures favours the bonding changes required for the formation of the new C C single bonds along polar cycloaddition reactions. Analysis of the reactivity indice…
Theoretical study of the molecular structure and the stability of neutral and reduced tetracyanoethylene
2003
Abstract The molecular structure and the stability of neutral, anionic, and dianionic tetracyanoethylene (TCNE) have been studied with MP2, coupled-cluster (CC), and density functional theory (DFT) procedures. The optimized geometries are in agreement with the available experimental data, although significant deviations for the CN bond distance have been obtained at the MP2 level. The adiabatic electron affinity of TCNE calculated with the B3LYP method is overestimated by 0.32 eV. In the light of the CC results, the source of such an overestimation is suggested to lie on the theoretical approach, rather than on a too low experimental value.
Double-balloon enteroscopy-facilitated cyanoacrylate-injection endotherapy of small-bowel varices: an international experience from 2 European tertia…
2019
Background and Aims Small-bowel varices (SBVs) are an uncommon consequence of portal hypertension. Radiologic intervention is usually considered for first-line management. When radiologic intervention is not possible, management options become very limited. The aim of this study was to evaluate the usefulness of double-balloon enteroscopy (DBE)-facilitated cyanoacrylate-injection endotherapy of SBVs. Methods This was a retrospective review of DBE-facilitated cyanoacrylate-injection endotherapy of SBVs (December 2015 to October 2016). Results Ten DBEs were performed in 6 patients (4 women; median age, 68.5 years). No radiologic or surgical options were deemed feasible. Thirteen nests of SBVs…