1806-29-7Relevant articles and documents
Products, rates, and mechanism of the gas-phase condensation of phenoxy radicals between 500-840 K
Wiater, Izabela,Born, Jan G. P.,Louw, Robert
, p. 921 - 928 (2000)
Phenols are demonstrated precursors of 'dioxins' - polychlorinated dibenzo-p-dioxins (DDs) and dibenzofurans (DFs) - in thermal processes, especially incineration. Heterogeneous catalysis, depending on conditions, can play an important role, but mere gas-phase combination of phenolic entities to ultimately DD and/or DF is always possible. The present paper addresses the fundamental role of phenol itself. Phenol has long been known to give DF upon pyrolysis and in similar thermal reactions. In the liquid phase under oxidative conditions it yields five condensation products (A-E); this clearly occurs through the dimerization of two phenoxy (PhO) radicals, followed by enolisation/rearomatisation. Our study shows that in the gas phase, at the lower T end, such dimers are also formed, but still with very little DF. That DF, indeed, is almost the only condensation product at elevated temperatures is substantiated by thermochemical-kinetic analysis (favouring the pathway of ortho-C/ortho-C combination of two PhO radicals), as well as by results obtained with two plausible intermediates, viz. 2,2'- dihydroxybiphenyl (A) and 2-phenoxyphenol (C). Mechanisms for the requisite enolisation and dehydration steps leading to DF are discussed.
THE ROLE OF STEREOELECTRONIC FACTORS IN THE OXIDATION OF PHENOLS
Armstrong, David R.,Breckenridge, Robin J.,Cameron, Colin,Nonhebel, Derek C.,Pauson, Peter L.,Perkins, Peter G.
, p. 1071 - 1074 (1983)
The oxidative coupling of both 3,5-dimethylphenol and phenol leads to the ortho-ortho and ortho-para coupled products as the predominant C-C dimers: stereoelectronic factors determine the preferred mode of approach of the phenoxyl radicals.
Synthesis of the spirocyclic cyclohexadienone ring system of the schiarisanrins.
Coleman,Guernon,Roland
, p. 277 - 280 (2000)
[structure: see text] Studies on the synthesis of the spirocyclic cyclohexadienone ring system 2 of the schiarisanrin family of natural products 1 are described and were based on the Lewis acid-promoted C-alkylation of the corresponding phenolic precursor.
CuO grafted triazine functionalized covalent organic framework as an efficient catalyst for C-C homo coupling reaction
Das, Sabuj Kanti,Krishna Chandra, Bijan,Molla, Rostam A.,Sengupta, Manideepa,Islam, Sk. Manirul,Majee, Adinath,Bhaumik, Asim
, (2020)
Designing of low cost catalytic system for new C-C bond formation reactions is very challenging in synthetic organic chemistry. Herein, we report a new copper oxide immobilized covalent organic framework (COF) material CuII-TRIPTA by grafting of CuO nanoparticles at the surface of a nitrogen rich porous COF material TRIPTA. TRIPTA has been synthesized through the extended Schiff base reaction between 2,4,6-triformylphloroglucinol and 1,3,5-tris-(4-aminophenyl) triazine. The COF as well as CuO loaded materials are characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and EPR spectroscopic analyses. CuII-TRIPTA material has been successfully applied as heterogeneous nanocatalyst for the C-C homo-coupling reaction of phenylboronic acids to synthesise wide range of biaryl compounds under mild and eco-friendly conditions (60 °C, methanol solvent). Remarkably high specific surface area of CuII-TRIPTA (583 m2 g?1) and highly accessible catalytic sites in the 2D-hexagonal COF nano-architecture potentially makes it excellent catalyst in the C-C bond formation reaction, which is evident from the high TON of the catalyst in this reaction. The catalyst was recollected and reused till 6th cycles without any noticeable change of its catalytic activity, suggesting its high catalytic efficiency in this C-C bond formation reaction.
Photochemistry of Dibenzo-1,4-dioxin: Formation of 2,2'-Biphenylquinone as an Observable Intermediate
Guan, Bing,Wan, Peter
, p. 409 - 410 (1993)
Photolysis of dibenzo-1,4-dioxin 1, which is parent ring system of the well-known environmental contaminant 'dioxin' an 2,3,7,8-tetramethyldibenzo-1,4-dioxin 2, in aqueous solution results in an novel intramolecular rearrangement, giving rise to intermedi
Photochemical rearrangement of chlorinated dibenzo-p-dioxins. Regioselective carbon-oxygen bond homolysis from the singlet excited state, and carbon-chlorine bond homolysis from the triplet excited state
Kobayashi, Takanori,Shimada, Jun-Ichi,Kitahara, Chieko,Haga, Naoki
, p. 348 - 349 (2006)
UV light irradiation of 1-chloro-, 2-chloro-, 1,2-dichloro-, 2,3-dichloro-, and 2,7-dichlorodibenzo-p-dioxin in methanol leads to regioselective homolysis of carbon-oxygen bond from the singlet excited state to undergo rearrangement into chlorinated 2,2′-biphenols. On the contrary, reaction from the triplet excited state of chlorinated dioxins results in selective formation of dechlorinated congeners without altering the dioxin skeleton. Copyright
Small Molecule NF-κB Inhibitors as Immune Potentiators for Enhancement of Vaccine Adjuvants
Moser, Brittany A.,Escalante-Buendia, Yoseline,Steinhardt, Rachel C.,Rosenberger, Matthew G.,Cassaidy, Britteny J.,Naorem, Nihesh,Chon, Alfred C.,Nguyen, Minh H.,Tran, Ngoctran T.,Esser-Kahn, Aaron P.
, (2020)
Adjuvants are added to vaccines to enhance the immune response and provide increased protection against disease. In the last decade, hundreds of synthetic immune adjuvants have been created, but many induce undesirable levels of proinflammatory cytokines including TNF-α and IL-6. Here we present small molecule NF-κB inhibitors that can be used in combination with an immune adjuvant to both decrease markers associated with poor tolerability and improve the protective response of vaccination. Additionally, we synthesize a library of honokiol derivatives identifying several promising candidates for use in vaccine formulations.
Phenol conversion and dimeric intermediates in horseradish peroxidase-catalyzed phenol removal from water
Jian Yu,Taylor,Huixian Zou,Biswas,Bewtra
, p. 2154 - 2160 (1994)
Phenol was removed from water by horseradish peroxidase-catalyzed polymerization. Five dimeric and one trimeric products from the reaction were identified in the aqueous solution. A peroxidase inactivation model for the reaction in the presence of poly(et
SECOND-ORDER COMBINATION REACTION OF PHENOXYL RADICALS
Ye, Mingyu,Schuler, Robert H.
, p. 1898 - 1902 (1989)
Phenoxy radicals, when produced pulse radiolytically at concentrations > 1E-4 M, combine in second-order processes to give 2,2'-, 2,4', and 4,4'-dihydroxybiphenyl as the predominant products.The ratios of these products observed under a variety of conditi
Dendrimer-encapsulated Pd nanoparticles as aqueous, room-temperature catalysts for the Stille reaction
Garcia-Martinez, Joaquin C.,Lezutekong, Raphael,Crooks, Richard M.
, p. 5097 - 5103 (2005)
We report that dendrimer-encapsulated Pd nanoparticles having a diameter of ～1.7 nm are effective and general catalysts for coupling aryl halides to organostannanes (the Stille reaction) under mild conditions. The significant results of this study are that the Stille reaction is catalyzed by dendrimer-encapsulated Pd nanoparticles in very good yield, in aqueous solution at 23 °C, and using only 0.100 atom % of Pd as catalyst.
