Towards the Synthesis of a Dewar Furan Stabilized by a Pinching Group: the Role of Dewar o-Xylylenes as Dienes and Dienophiles

1991 ◽  
Vol 44 (9) ◽  
pp. 1293 ◽  
Author(s):  
RN Warrener ◽  
IG Pitt ◽  
RA Russell
Keyword(s):  
Active Species ◽  
Diels Alder

The synthesis of a photosubstrate (42) suitable for the production of a Dewar furan (46) containing a four-carbon bridge at the 1,4-position is described. The route to this product illustrates an example of transfer technology in synthesis, by using the oxanorbornadiene (29). Other active species such as Dewar benzene (32) and Dewar o-xylylene (50) play key roles as intermediates. Diels-Alder cycloadditions are also central to the overall strategy, and some observations are made regarding the facial specificities operating, especially in regard to Dewar o-xylylene (50) and its dimerization. Attempts to isolate the photoproducts, presumably involving the Dewar furan (46) as intermediate, were unsuccessful.

Sewage sludge as a precursor of adsorbents/catalysts for environmental applications

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
A. Ros ◽  
C. Canals-Batlle ◽  
M.A. Lillo-Ródenas ◽  
E. Fuente ◽  
M. A. Montes-Morán ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Room Temperature ◽  
Waste Water Treatment ◽  
Textural Properties ◽  
Active Species ◽  
Elemental Sulphur ◽  
Gaseous Emissions ◽  
Removal Experiments ◽  
Catalytically Active

This paper focuses on the valorisation of solid residues obtained from the thermal treatment of sewage sludge. In particular, sewage sludge samples were collected from two waste water treatment plants (WWTPs) with different sludge line basic operations. After drying, sludges were heated up to 700 °C in appropriate ovens under diluted air (gasification) and inert (pyrolysis) atmospheres. The solids obtained, as well as the dried (raw) sludges, were characterised to determine their textural properties and chemical composition, including the speciation of their inorganic fraction. All the materials under study were employed as adsorbents/catalysts in H2S removal experiments at room temperature. It was found that, depending on the particular sludge characteristics, outstanding results can be achieved both in terms of retention capacities and selectivity. Some of the solids outperform commercially available sorbents specially designed for gaseous emissions control. In these adsorbents/catalysts, H2S is selectively oxidised to elemental sulphur most likely due to the presence of inorganic, catalytically active species. The role of the carbon-enriched part on these solids is also remarked.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

Converting the role of LiClO4 from salting-in to salting-out in Diels-Alder reactions by solvent manipulation

2003 ◽  
Vol 16 (9) ◽  
pp. 633-635 ◽  
Author(s):  
Suvarna S. Deshpande ◽  
Sanjay S. Pawar ◽  
Usha Phalgune ◽  
Anil Kumar
Keyword(s):  
Diels Alder ◽  
Salting Out

ChemInform Abstract: Switched Role of Fullerene in the Diels-Alder Reaction: Facile Addition of Dienophiles to the Conjugated Fullerene Diene Moiety.

ChemInform ◽  
2009 ◽  
Vol 40 (24) ◽  
Author(s):  
Jiayao Yao ◽  
Zuo Xiao ◽  
Jianxin Zhang ◽  
Xiaobing Yang ◽  
Liangbing Gan ◽  
...  
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

In situ synthesis of hierarchical nitrogen-doped MoS2 microsphere with an excellent visible light-driven photocatalytic nitrogen fixation ability

2020 ◽  
Vol 13 (05) ◽  
pp. 2051031
Author(s):  
Abulikemu Abulizi ◽  
Hujiabudula Maimaitizi ◽  
Dilinuer Talifu ◽  
Yalkunjan Tursun
Keyword(s):  
Visible Light ◽  
High Performance ◽  
Nucleation Site ◽  
Active Species ◽  
Nitrogen Doped ◽  
Photogenerated Electrons ◽  
The Hierarchical Structure ◽  
Visible Light Driven

A photocatalyst of high-performance hierarchical nitrogen-doped MoS2 (N-MoS2) microsphere was fabricated by an in situ hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB). The as-prepared N-MoS2 microsphere was self-assembled by extremely thin interleaving petals, where CTAB acts as a nucleation site for the formation of the interleaving petals due to the strong interaction between CTA+ and [Formula: see text]. N-MoS2 showed higher N2 fixation ability (101.2 [Formula: see text] mol/g(cat)h) than the non-doped MoS2 under the visible light irradiation, and the improved photocatalytic activity could be ascribed to that the doped N narrows the band gap, and the surface reflecting and scattering effect caused by the hierarchical structure enhance the light adsorption. The trapping experiment of active species was also investigated to evaluate the role of photogenerated electrons in the photocatalytic reaction process. Meanwhile, the possible mechanism for the formation and excellent photocatalytic performance of N-MoS2 microsphere were also presented.

scholarly journals Fabrication of MgFe2O4-ZnO Nanocomposites for Photocatalysis of Organic Pollutants under Solar Light Radiation

2019 ◽  
Vol 31 (12) ◽  
pp. 2995-3003
Author(s):  
Krushitha Shetty ◽  
B.S. Prathibha ◽  
Dinesh Rangappa ◽  
K.S. Anatharaju ◽  
H.P. Nagaswarupa ◽  
...  
Keyword(s):  
Band Gap ◽  
Active Species ◽  
Solution Combustion ◽  
Quantization Effect ◽  
Photocatalytic Activities ◽  
Efficient Charge ◽  
Temperature Solution ◽  
Uv Visible ◽  
Photocatalytic Applications

MgFe2O4, ZnO and MgFe2O4-ZnO samples were successfully prepared through low temperature solution combustion route. The structural and morphological investigation were accomplished by PXRD, HRSEM, UV-visible and FTIR. The PXRD results point towards the reduced size of synthesized nanocomposites, which was further confirmed by HRSEM studies. Optical properties of the prepared samples were examined by UV-visible spectroscopy. The band gap seems to be widened for prepared nanocomposites compared to pure MgFe2O4. The photocatalytic degradation of methylene blue under sunlight was superior in contrast to pure MgFe2O4 and ZnO. MgFe2O4-ZnO (1:1) acts as the most effective photocatalyst activity compared to pure MgFe2O4 and ZnO. EIS data was proven to be an efficient tool for understanding the electronic properties for photocatalytic studies. The enhanced sunlight-driven photocatalytic activities of MgFe2O4-ZnO nanocomposite is supported by the factors such as quantization effect, band gap widening and efficient charge separation. MgFe2O4-ZnO showed excellent reusability with high photocatalytic efficiencies suggesting its suitability for solar photocatalytic applications. Additionally, scavenging test was conducted to know the role of all active species during photoelectrocatalysis. This work presents a facile and effective route for the construction of MgFe2O4-ZnO nanocomposites with intriguing structures and multiple functions.

scholarly journals Ubiquitin Extension Protein UEP1 Modulates Cell Death and Resistance to Various Pathogens in Tobacco

2019 ◽  
Vol 109 (7) ◽  
pp. 1257-1269
Author(s):  
You-Ping Xu ◽  
Yuan Zhao ◽  
Xiao-Yi Song ◽  
Yun-Feng Ye ◽  
Ren-Gang Wang ◽  
...  
Keyword(s):  
Cell Death ◽  
Disease Resistance ◽  
Ribosomal Protein ◽  
Mosaic Virus ◽  
Amine Oxidase ◽  
Active Species ◽  
26S Proteasome ◽  
Virus Induced Gene Silencing ◽  
Copper Amine Oxidase

Ubiquitin (Ub) extension proteins (UEPs) are fusion proteins of a Ub at the N terminus to a ribosomal protein. They are the main source of Ub and the only source of extension ribosomal protein. Although important roles of the Ub-26S proteasome system in various biological processes have been well established, direct evidence for the role of UEP genes in plant defense is rarely reported. In this study, we cloned a Ub-S27a-type UEP gene (NbUEP1) from Nicotiana benthamiana and demonstrated its function in cell death and disease resistance. Virus-induced gene silencing of NbUEP1 led to intensive cell death, culminating in whole-seedling withering. Transient RNA interference (RNAi) of NbUEP1 caused strong cell death in infiltrated areas, while stable NbUEP1-RNAi tobacco plants constitutively formed necrotic lesions in leaves. NbUEP1-RNAi plants exhibited increased resistance to the oomycete Pythium aphanidermatum and viruses Tobacco mosaic virus and Cucumber mosaic virus while displaying decreased resistance to the nematode Meloidogyne incognita compared with non-RNAi control plants. Transcription profiling analysis indicated that jasmonate and ethylene pathways, lipid metabolism, copper amine oxidase-mediated active species generation, glycine-rich proteins, vacuolar processing enzyme- and RD21-mediated cell death and defense regulation, and autophagy might be associated with NbUEP1-mediated cell death and resistance. Our results provided evidence for the important roles of plant UEPs in modulating plant cell death and disease resistance.

Concerted and Diradical Stepwise Mechanisms in the Diels-Alder Reactions of Phosphinine and Phosphinine Sulfide: A DFT Investigation

2008 ◽  
Vol 63 (3) ◽  
pp. 321-330 ◽  
Author(s):  
Raj K. Bansal ◽  
Neelima Gupta ◽  
Surendra K. Kumawat
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Diels Alder ◽  
Dimethyl Acetylenedicarboxylate ◽  
Functional Theory ◽  
Concerted Mechanism ◽  
Density Functional Theory Level ◽  
The Density Functional Theory

Computations of the concerted and diradical stepwise mechanisms of the Diels-Alder (DA) reactions on the >C=P− functionality of phosphinine and phosphinine sulfide with 1,3-butadiene at the density functional theory level B3LYP/6-311++G**//B3LYP/6-31G** give the values of energy of concert as 10.7 and 2.6 kcal mol−1, respectively. Similarly, the DA reaction of dimethyl acetylenedicarboxylate (DMAD) with the −CH=CH−CH=P− moiety of phosphinine or its sulfide has been investigated theoretically at the same level of theory. The results reveal that in the DA reaction of phosphinine, the role of sulfur is to oxidize phosphorus to generate a phosphinine sulfide intermediate, which subsequently undergoes DA reaction with 2,3-dimethylbutadiene or DMAD by a concerted mechanism to afford the respective cycloadducts.

ChemInform Abstract: Highly Diastereoselective Diels-Alder Reaction Mediated by a Chiral Auxiliary Derived from Amino Indanol: The Role of Conformation on Diastereoselectivity.

ChemInform ◽  
2010 ◽  
Vol 27 (5) ◽  
pp. no-no
Author(s):  
I. W. DAVIES ◽  
C. H. SENANAYAKE ◽  
L. CASTONGUAY ◽  
R. D. LARSEN ◽  
T. R. VERHOEVEN ◽  
...  
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Chiral Auxiliary ◽  
Diels Alder Reaction
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