- Copper-catalyzed oxidative methyl-esterification of 5-hydroxymethylfurfural using TBHP as an oxidizing and methylating reagent: A new approach for the synthesis of furan-2,5-dimethylcarboxylate
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Catalytic conversion of 5-hydroxymethylfurfural (HMF) into furan-2,5-dimethylcarboxylate (FDMC) is of great significance in the production of polyethylene furanoate (PEF), a renewable biomass-derived polymer that can replace the fossil dependent polyethylene terephthalate (PET). Herein, for the first time, we report the synthesis of FDMC from oxidative methyl-esterification of HMF using tert-butyl hydroperoxide (TBHP) as an oxidizing and methylating reagent catalyzed by mesoporous alumina nanospheres-embedded with CuO nanoparticles (CuO/m-Al2O3). The CuO/m-Al2O3 catalysts with different copper contents were prepared by evaporation-induced self-assembly of a structure-directing agent (Pluronic P-123). The decomposition of P-123 during calcination in air results into the formation of a mesoporous structure with highly dispersed CuO nanoparticles. The as-prepared 6-CuO/m-Al2O3 exhibits excellent catalytic activity towards oxidative methyl-esterification of HMF into FDMC with 92% yield and turnover frequency (TOF) of 0.56 h?1. Furthermore, oxidative methyl-esterification of a range of substrates through SP3 C[sbnd]H bond functionalization has also been demonstrated using the same catalyst.
- Gupta, Shyam Sunder R.,Kantam, Mannepalli Lakshmi,Vinu, Ajayan
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p. 259 - 269
(2020/06/27)
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- Ligand-free Cu(ii)-catalyzed aerobic etherification of aryl halides with silanes: An experimental and theoretical approach
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Owing to their wide occurrence in nature and immense applications in various fields, the synthesis of aryl alkyl ethers has remained a focus of interest. In contrast to the conventional/traditional methods of etherification, herein, we have reported a more efficient method, which is better yielding and more general in application. The etherification of aryl halides by alkoxy/phenoxy silanes was catalyzed by copper acetate in the presence of cesium carbonate and oxygen in DMF at 145 °C. All the as-synthesized compounds were characterized via the 1H-NMR and 13C-NMR spectroscopic techniques. Density functional theory calculations using the B3LYP functional were performed to elucidate the reaction mechanism. The C-O coupling reaction between 2-nitroiodobenzene and tetramethoxysilane was used as a model reaction. The activation energy barriers for the generation of catalytic species (31.6 kcal mol-1) and the σ-bond metathesis (16.0 kcal mol-1), oxidative addition/reductive elimination (20.3 kcal mol-1), halogen atom transfer (19.2 kcal mol-1) and single electron transfer (SET) (29.5 kcal mol-1) mechanisms for the C-O coupling reaction were calculated. Calculations for the key reaction steps were repeated with the B3PW91, PBEH1PBE, wB97XD, CAM-B3LYP and mPW1LYP functionals. The formation of catalytic species via a single electron transfer reaction between tetramethoxysilane and copper acetate, formation of methoxy radicals and methoxylation of copper showed an overall energy barrier of 31.6 kcal mol-1, and therefore is the rate determining step.
- Ahmed, Muhammad Naeem,Ahmad, Khalil,Yasin, Khawaja Ansar,Farooq, Tayyaba,Khan, Bilal Ahmad,Roy, Soumendra K.
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p. 11316 - 11333
(2019/07/31)
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- SULPHAMOYLARYL DERIVATIVES AND USE THEREOF AS MEDICAMENTS FOR THE TREATMENT OF LIVER FIBROSIS
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Potent 5-HT2B antagonist of Formula (A), including stereochemically isomeric forms, and salts, hydrates, solvates thereof and their use wherein R1 to R4 and Ar have the meaning as defined herein. The present invention also relates to processes for preparing said compounds, pharmaceutical compositions containing them, alone or in combination with other drugs, in fibrosis and/or cirrhosis prevention or therapy.
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Page/Page column 91
(2018/09/08)
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- N-3-substituted imidazoquinazolinones: Potent and selective PDE5 inhibitors as potential agents for treatment of erectile dysfunction
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Phosphodiesterase type 5 (PDE5) inhibitors with improved PDE isozyme selectivity relative to sildenafil may result in agents for the treatment of male erectile dysfunction (MED) with a lower incidence of PDE-associated adverse effects. This paper describe
- Rotella, David P.,Sun, Zhong,Zhu, Yeheng,Krupinski, John,Pongrac, Ronald,Seliger, Laurie,Normandin, Diane,Macor, John E.
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p. 1257 - 1263
(2007/10/03)
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- Optimization of substituted N-3-benzylimidazoquinazolinone sulfonamides as potent and selective PDE5 inhibitors
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A previous report from these laboratories identified the N-3-benzylimidazoquinazolinone nucleus as a more selective PDE5 inhibitor template compared to the pyrazolopyrimidine of sildenafil. This paper describes in detail the structure-activity relationshi
- Rotella,Sun,Zhu,Krupinski,Pongrac,Seliger,Normandin,Macor
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p. 5037 - 5043
(2007/10/03)
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- Cyclic Nucleotide Phosphodiesterase Inhibition by Imidazopyridines: Analogues of Sulmazole and Isomazole as Inhibitors of the cGMP Specific Phosphodiesterase
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The synthesis and phosphodiesterase (PDE) inhibitory profile of a series of imidazopyridines, including sulmazole and isomazole, on separated PDE isoenzymes are described.The results show that both sulmazole and isomazole are weak inhibitors of PDE III, and their inotropic activity is unlikely to be due to PDE III inhibition alone.Surprisingly, both compounds were found to be significant inhibitors of the cGMP specific isoenzyme, PDE V, and a series of simple 2-substituted phenylimidazopyridines have been made to investigate the SAR of PDE activity.This has been shown to be sensitive to chain length, polarity, and the nature of the heteroatom linking group.Potent PDE V inhibitors, many of which are also significant inhibitors of PDE IV, have been identified.
- Coates, William J.,Connolly, Brendan,Dhanak, Dashyant,Flynn, Sean T.,Worby, Angela
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p. 1387 - 1392
(2007/10/02)
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- Radical isomerization via intramolecular ipso substitution of aryl ethers: Aryl translocation from oxygen to carbon
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Bromopropyl aryl ethers an converted to 3-arylpropanols under standard radical generating conditions in the presence of tributylstannane and AIBN. This rearrangement involves intramolecular ipso attack of the alkyl radicals which generates spiro cyclohexadienyl radical intermediates.
- Lee, Eun,Lee, Chulbom,Tae, Jin Sung,Whang, Ho Sung,Li, Kap Sok
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p. 2343 - 2346
(2007/10/02)
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