- Towards mesostructured zinc imidazolate frameworks
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The transfer of supramolecular templating to the realm of metal-organic frameworks opens up new avenues to the design of novel hierarchically structured materials. We demonstrate the first synthesis of mesostructured zinc imidazolates in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB), which acts as a template giving rise to ordered lamellar hybrid materials. A high degree of order spanning the atomic and mesoscale was ascertained by powder X-ray diffraction, electron diffraction, as well as solid-state NMR and IR spectroscopy. The metrics of the unit cells obtained for the zinc methylimidazolate and imidazolate species are a=(11.43±0.45), b=(9.55±0.35), c=(27.19±0.34)A, and a=(10.98±0.90), b=(8.95±0.95), c=(26.33±0.34)A, respectively, assuming orthorhombic symmetry. The derived structure model is consistent with a mesolamellar structure composed of bromine-terminated zinc (methyl)imidazolate chains interleaved with motionally rigid cationic surfactant molecules in an all-trans conformation. The hybrid materials exhibit unusually high thermal stability up to 300°C, at which point CTAB is lost and evidence for a thermally induced transformation into poorly crystalline mesostructures with larger feature sizes is obtained. Treatment with ethanol effects the extraction of CTAB from the material, followed by facile transformation into pure microporous ZIF-8 nanoparticles within minutes, thus demonstrating a unique transition from a mesostructure into a microporous zinc imidazolate.
- Junggeburth, Sebastian C.,Schwinghammer, Katharina,Virdi, Kulpreet S.,Scheu, Christina,Lotsch, Bettina V.
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- Hypocholesterolemic activity of hesperetin derivatives
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Hesperetin ester and ether derivatives possessing a long alkyl chain were synthesized for examining their hypocholesterolemic activities in high cholesterol-fed mice. Hesperetin 7-O-lauryl ether (4b) and hesperetin 7-O-oleyl ether (4e) exhibited strong cholesterol-lowering effects.
- Jeong, Tae-Sook,Kim, Eun Eai,Lee, Chul-Ho,Oh, Jung-Hoon,Moon, Surk-Sik,Lee, Woo Song,Oh, Goo-Taeg,Lee, Sangku,Bok, Song-Hae
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- Thiourea-Mediated Halogenation of Alcohols
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The halogenation of alcohols under mild conditions expedited by the presence of substoichiometric amounts of thiourea additives is presented. The amount of thiourea added dictates the pathway of the reaction, which may diverge from the desired halogenation reaction toward oxidation of the alcohol, in the absence of thiourea, or toward starting material recovery when excess thiourea is used. Both bromination and chlorination were highly efficient for primary, secondary, tertiary, and benzyl alcohols and tolerate a broad range of functional groups. Detailed electron paramagnetic resonance (EPR) studies, isotopic labeling, and other control experiments suggest a radical-based mechanism. The fact that the reaction is carried out at ambient conditions, uses ubiquitous and inexpensive reagents, boasts a wide scope, and can be made highly atom economic, makes this new methodology a very appealing option for this archetypical organic reaction.
- Mohite, Amar R.,Phatake, Ravindra S.,Dubey, Pooja,Agbaria, Mohamed,Shames, Alexander I.,Lemcoff, N. Gabriel,Reany, Ofer
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supporting information
p. 12901 - 12911
(2020/11/26)
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- Vinyl Sulfonates: A Click Function for Coupling-and-Decoupling Chemistry and their Applications
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The term coupling-and-decoupling (CAD) chemistry refers to applications in which efficient bond formation and subsequent cleavage between two moieties is required. Within this context, the scope of the vinyl sulfonate (VSO) group as an efficient tool for CAD chemistry is reported. The coupling step relies on the click features of the Michael-type addition of diverse nucleophiles to vinyl sulfonates as a valuable methodology. The feasibility of this strategy has been proved by the high yields obtained in mild conditions with model VSO derivatives. Cleavage of the resulting sulfonate adducts either through nucleophilic substitution with different nucleophiles (for alkyl VSO groups) or through hydrolysis (for both alkyl and aryl VSO) are successful strategies for the decoupling step, the former being the most promising, as the reaction proceeds under milder conditions with thiol nucleophiles. Moreover, the click VSO coupling chemistry proves to be orthogonal with the click CuAAC reaction, which enables the VSO-CAD methodology for the preparation of hetero-bifunctional clickable and cleavable linkers for double click modular strategies. The potential of the VSO-CAD chemistry is demonstrated in two biologically relevant examples: the decoupling of sulfonates with glutathione (GSH) under conditions compatible with those of living systems; and the synthesis of homo- and heterogeneous multivalent glycosylated systems from 1-thio and 1-azido or 1-azidoethyl sugar derivatives and bis-vinyl sulfonates (homo systems) or alkynyl-VSO bifunctional clickable-cleavable linkers (hetero systems). As proof of concept, the cleavable character of these multivalent systems was demonstrated by using one of them as a reversible linker for the non-covalent assembling and chemical decoupling of two model lectins. (Figure presented.).
- Cruz, Carlos M.,Ortega-Mu?oz, Mariano,López-Jaramillo, F. Javier,Hernández-Mateo, Fernando,Blanco, Victor,Santoyo-González, Francisco
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p. 3394 - 3413
(2016/11/13)
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- A mild and efficient method for bromination of alcohols using α,α-dibromo-β-dicarbonyl compounds as halogen sources
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Exploration of α,α-dibromo-β-dicarbonyl compounds as novel bromine agents for the conversion of alcohols to alkyl bromides under neutral conditions has been achieved. This method can be used for acid-sensitive substrates and allows the bromination of various primary and secondary alcohols to proceed at room temperature within a very short period of time.
- Cui, Xiao-Meng,Guan, Yong-Hong,Li, Na,Lv, Hao,Fu, Lin-An,Guo, Kun,Fan, Xiaohui
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supporting information
p. 90 - 93
(2014/01/06)
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- Syntheses of long-chain quaternary ammonium salts from fatty alcohols by microwave irradiation
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The phase-transfer catalysts, long-chain quaternary ammonium salts, were rapidly synthesized from fatty alcohols by the reactions with hydrogen halides in the presence of trialkyl amines under microwave irradiation. The catalysts could be widely applied in a variety of quick and new organic reactions, whether by conventional heating or under microwave irradiation. The reaction efficiencies under microwave irradiation were higher than those obtained with conventional heating.
- Jiang,Hu,Pang,Yuan
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p. 847 - 850
(2007/10/03)
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- A Convenient Conversion of Primary Amines into the Corresponding Halides Radical Promoted Halodeamination via N-Substituted-N-Tosylhydrazines
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Treatment of 1-substituted-1-tosylhydrazines with 2 equivalents of NCS or NBS in dry THF in presence of light affords the corresponding alkyl halides in good yields.This reaction presumably involves the initial formation of a stabilized hydrazyl radical which is halogenated in a radical chain process.Elimination of p-toluenesulfinic acid and extrusion of nitrogen leads to the corresponding alkyl halide.This route provides an improved method for halodeamination under neutral reaction conditions.
- Collazo, Luis R.,Guziec, Frank S.,Hu, Wei-Xiao Jr.,Pankayatselvan, Ratnadevi
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p. 7911 - 7914
(2007/10/02)
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- Synthesis of 1-palmitoyl-2-hexadecyl-sn-glycero-3-phospholine (PHPC)
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A general method for the chirospecific synthesis of 1-acyl-2-alkyl-sn-glycero-3-phosphocholines is described. 1-Palmityl-2-hexadecyl-sn-glycero-3-phosphocholine (PHPC) was synthesized in 18percent overall yield in ten steps via five new synthetic intermediates, and 1-acetyl-2-hexadecyl-sn-glycero-3-phosphocholine (AHPC) was also synthesized. 1-Acetyl-2-alkyl-sn-glycero-3-phosphocholines, which have not been found to exist in nature, are ether lipid analogs of 1,2-diacetyl-sn-glycero-3-phosphocholines, which are important components of cell membranes.Biophysical studies of hydrated bilayers of PHPC will be of interest in probing the critical importance of the central region of these amphiphilic molecules to the molecular assemblies that are found. Key words: 1-Acetyl-2-alkyl-sn-glycero-3-phosphocholine; 1-Palmitoyl-2-hexadecyl-sn-glycero-3-phosphocholine; PHPC; 1-acetyl-2-hexadecyl-sn-glycero-3-phosphocholine; AHPC; Palmitic anhydride
- Duclos, Richard I.
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p. 161 - 170
(2007/10/02)
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- A FACILE METHOD FOR THE CONVERSION OF PRIMARY ALKYL CHLORIDES TO THE CORRESPONDING BROMIDES
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Treatment of several representative primary alkyl chlorides with one equivalent of sodium bromide in 2:1 (v/v) N,N-dimethylformamide : dibromoethane at 100 deg C for several hours resulted in their quantitative conversion to the corresponding bromides.
- Babler, James H.,Spina, Kenneth P.
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p. 1313 - 1320
(2007/10/02)
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- OXIDATION OF N-ALKYL-N'-TOSYLHYDRAZINES WITH BROMINE
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Oxidation of N-alkyl-N'-tosylhydrazines with bromine yield alkyl bromides, vicinal alkyl dibromides and traces of alcohols.The main products of primary hydrazines are monobromides whereas secondary hydrazines preferably produce dibromides.The reaction proceeds with evolution of nitrogen and hydrobromic acid and by the formation of intermediate sulfinic ester wich may be isolated.Various substrates were examined under different conditions to confirm the validity of the reaction mechanism hypothesized.
- Palmieri, Gianni
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p. 4097 - 4102
(2007/10/02)
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- PREPARATION OF ALKYL HALIDES VIA ORGANOTELLURIUMS
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The conversion of phenyltelluroalkanes to haloalkanes was studied in connection with the homologation of alkyl halides.Similar reactions of 1,1-bis(phenyltelluro)alkanes provided a new synthetic method of aldehydes.
- Chikamatsu, Kiyofumi,Otsubo, Tetsuo,Ogura, Fumio,Yamaguchi, Hachiro
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p. 1081 - 1084
(2007/10/02)
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