The Experts below are selected from a list of 4509 Experts worldwide ranked by ideXlab platform
Marcello Tiecco - One of the best experts on this subject based on the ideXlab platform.
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preparation of the first bench stable phenyl selenolate an interesting on water Nucleophilic Reagent
European Journal of Organic Chemistry, 2008Co-Authors: Claudio Santi, Benedetta Battistelli, Stefano Santoro, Lorenzo Testaferri, Marcello TieccoAbstract:In this communication we report the synthesis and the characterization of the first solid and air-stable selenolates, starting from commercially available phenylselenenyl halides and elemental zinc. These Reagents were efficiently employed in the ring opening of epoxides as well as in other Nucleophilic substitution and addition reactions showing an unexpected rate acceleration in water suspension at room temperature. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Preparation of the First Bench‐Stable Phenyl Selenolate: an Interesting “On Water” Nucleophilic Reagent
European Journal of Organic Chemistry, 2008Co-Authors: Claudio Santi, Benedetta Battistelli, Stefano Santoro, Lorenzo Testaferri, Marcello TieccoAbstract:In this communication we report the synthesis and the characterization of the first solid and air-stable selenolates, starting from commercially available phenylselenenyl halides and elemental zinc. These Reagents were efficiently employed in the ring opening of epoxides as well as in other Nucleophilic substitution and addition reactions showing an unexpected rate acceleration in water suspension at room temperature. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Wei Zhang - One of the best experts on this subject based on the ideXlab platform.
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Green preparation of branched biolubricant by chemically modifying waste cooking oil with lipase and ionic liquid
Journal of Cleaner Production, 2020Co-Authors: Wei Zhang, Yanliang Song, Wei Xiong, Changjing Chen, Biqiang Chen, Xu ZhangAbstract:Abstract To reduce the environment pollution from biolubricant synthesis, in this study, we developed a green and efficient strategy for the preparation of octylated branched biolubricant from waste cooking oil (WCO): (1) WCO was first hydrolyzed by a lipase (Candida sp. 99–125) to produce unsaturated fatty acids (UFAs), the latter was subsequently concentrated by urea complexation; (2) Next, we synthesized new esters using the UFAs as substrate via esterification with 2-ethylhexanol employing lipase (Novozym 435) and the new esters products were further epoxidated; (3) After that, the epoxy group was attacked by a low-cost Nucleophilic Reagent, octanoic acid, to prepare octylated branched biolubricant using an recyclable ionic liquid, [HMIm][PF6], as catalyst. After three recycling times, [HMIm][PF6] remained catalytic activity with a conversion yield of 81.22% and selectivity of 82.10%. The obtained product showed excellent lubricant properties, such as low pour point of −61 °C, high viscosity index of 149 and high thermal-oxidation stability (onset temperature of 326.35 °C and oxidative onset temperature of 312.06 °C). The high frequency reciprocating rig (HFRR) measurement demonstrated that lubrication performance (friction coefficient of 0.09 and wear spot diameter of 203 μm) was much better than that of mineral based lubricant with the same viscosity grade. Therefore, this study provided a critical synthetic strategy for preparing high-performance biolubricants from WCO.
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depolymerization and characterization of acacia mangium tannin for the preparation of mussel inspired fast curing tannin based phenolic resins
Chemical Engineering Journal, 2019Co-Authors: Wenjie Zhu, Shifeng Zhang, Qiang Gao, Changlei Xia, Wei ZhangAbstract:Abstract Similar to the 3,4-dihydroxy-L-phenylalanine (DOPA) structures in mussel adhesive proteins (MAPs), tannin contains abundant similar catechol structures in the flavonoid units, which might be developed into high-performance adhesives. In this study, Acacia mangium tannin (AMT) was depolymerized under acidic conditions with 2-methylfuran as a Nucleophilic Reagent. The depolymerized tannin (DAMT) was combined with polyethyleneimine (PEI) to prepare tannin-based phenolic resins to mimic the MAP systems. The investigation of the chemical structures of tannin indicated the successful reaction of 2-methylfuran onto the flavonoid units to increase the chemical reactivity, as evidenced by the MALDI-TOF-MS, GPC, 1H NMR, and FT-IR analyses. The as-prepared PEI and DAMT-modified phenolic (DTPF-PEI) resin showed a high cross-linking and three-dimensional network, resulting from the high reactivity of DAMT. Complex reactions were observed during the curing of the as-prepared resin, including Michael addition and/or Schiff base formation reactions between the amino groups of PEI and the ortho-quinone of tannins, as well as the condensation reactions between PEI and the phenolic resins. Compared with tannin-phenol-formaldehyde (TPF) resin, the gel time of the DTPF-PEI resin decreased from 630 s to 204 s (decreased by 67.6%), the mass loss after hydrolysis decreased by 26.3%, the bonding strength increased by 63.6% when cured at 135 °C, and the formaldehyde emission decreased by 64.4%. Such high performance might be contributed by the formation of highly cross-linked networks, as well as the hydrogen bonding and pi-cation interactions between the catechol structures and the adhered surfaces. With its outstanding performance, including fast curing rate, excellent adhesion properties, low formaldehyde emission, and high thermal stability, this newly developed adhesive has the potential to be used as an alternative of conventional phenol-formaldehyde resins.
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characterization and acid catalysed depolymerization of condensed tannins derived from larch bark
RSC Advances, 2017Co-Authors: Aibin Zhang, Shifeng Zhang, Wei ZhangAbstract:Condensed tannins from larch bark extracts are a natural renewable and eco-friendly material and are potential substitutes for phenolic petrochemicals. However, the wide application of tannin is restricted by its low reactivity. Therefore, the goal of this study was to enhance the reactivity of larch tannin by depolymerization and determine optimal reaction conditions. The structures of larch tannin and depolymerized larch tannin were characterized by Fourier transform infrared (FT-IR) spectroscopy, solid phase 13C-NMR and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. The thermal stability of larch tannin before and after depolymerization was evaluated by thermogravimetric analysis (TGA). The results indicated that the monomeric units of larch tannin were mainly composed of catechin/epicatechin, gallocatechin/epigallocatechin, catechin–gallocatechin esters, and stilbene glucosides. The presence of a catechin gallate dimer that had lost both gallic acid residues and a hydroxy group and a small amount of fisetinidin units were also observed. Additionally, a series of peaks corresponding to oligomers of larch tannin of up to 11 repeating units were observed from the MALDI-TOF MS data. Depolymerization treatment, especially using 2-mercaptoethanol as a Nucleophilic Reagent, was found to be beneficial to the enhancement of thermal stability. The optimization of the depolymerization reaction allowed the reaction to be completed in two hours, at 60 °C, using 2-mercaptoethanol as a nucleophile and 0.1 mol L−1 HCl. Many compounds of molecular weight less than 600 Da, mainly dimers and monomers, were obtained under these reaction conditions.
Georgii G. Furin - One of the best experts on this subject based on the ideXlab platform.
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Reactions of trimethylsilylpentafluorobenzene and triethylgermylpentafluorobenzene with Nucleophilic Reagents
Journal of Fluorine Chemistry, 1992Co-Authors: V. V. Bardin, L. N. Rogoza, I. V. Stennikova, Georgii G. FurinAbstract:Abstract This paper reports the results of studies on the reactions of trialkylsilyl- and germyl- pentafluorobenzenes with O-, N, S- and C-nucleophiles, and with LiAlH 4 . Depending on the nature of the Nucleophilic Reagent, its attack is oriented towards a heteroatom (RO − , RS − ), the C-4 atom of the pentafluorophenyl ring (BuLi, LiA1H 4 , piperidyl-lithium) or at both electrophilic centres (piperidine, RS − ).
Claudio Santi - One of the best experts on this subject based on the ideXlab platform.
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preparation of the first bench stable phenyl selenolate an interesting on water Nucleophilic Reagent
European Journal of Organic Chemistry, 2008Co-Authors: Claudio Santi, Benedetta Battistelli, Stefano Santoro, Lorenzo Testaferri, Marcello TieccoAbstract:In this communication we report the synthesis and the characterization of the first solid and air-stable selenolates, starting from commercially available phenylselenenyl halides and elemental zinc. These Reagents were efficiently employed in the ring opening of epoxides as well as in other Nucleophilic substitution and addition reactions showing an unexpected rate acceleration in water suspension at room temperature. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Preparation of the First Bench‐Stable Phenyl Selenolate: an Interesting “On Water” Nucleophilic Reagent
European Journal of Organic Chemistry, 2008Co-Authors: Claudio Santi, Benedetta Battistelli, Stefano Santoro, Lorenzo Testaferri, Marcello TieccoAbstract:In this communication we report the synthesis and the characterization of the first solid and air-stable selenolates, starting from commercially available phenylselenenyl halides and elemental zinc. These Reagents were efficiently employed in the ring opening of epoxides as well as in other Nucleophilic substitution and addition reactions showing an unexpected rate acceleration in water suspension at room temperature. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Qian Wan - One of the best experts on this subject based on the ideXlab platform.
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hydrogen bonding assisted exogenous Nucleophilic Reagent effect for β selective glycosylation of rare 3 amino sugars
Journal of the American Chemical Society, 2019Co-Authors: Jing Zeng, Ruobin Wang, Shuxin Zhang, Jing Fang, Shanshan Liu, Guangfei Sun, Ying Xiao, Wenqi Zhang, Qian WanAbstract:Challenges for stereoselective glycosylation of deoxy sugars are notorious in carbohydrate chemistry. We herein report a novel strategy for the construction of the less investigated β-glycosidic bonds of 3,5- trans-3-amino-2,3,6-trideoxy sugars (3,5- trans-3-ADSs), which constitute the core structure of several biologically important antibiotics. Current protocol leverages a C-3 axial sulfonamide group in 3,5- trans-3-ADSs as a hydrogen-bond (H-bond) donor and repurposes substoichiometric phosphine oxide as an exogenous Nucleophilic Reagent (exNu) to establish an intramolecular H-bond between the former and the derived α-oxyphosphonium ion. This pivotal interaction stabilizes the α-face-covered intermediate to inhibit the formation of the more reactive β-intermediate, thereby yielding reversed β-selectivity, which is unconventional for an exNu-mediated glycosylation system. A wide range of substrates was accommodated, and good to excellent β-selectivities were ensured by this H-bonding-assisted exNu effect. The robustness of the current strategy was further attested by the architectural modification of natural products and drugs containing 3,5- trans-3-ADSs, as well as the synthesis of a trisaccharide unit in avidinorubicin.
