Lyotropic liquid crystal-assisted synthesis of micro- and nanoparticles of silver

A simple, one-step approach for the synthesis of micro- and nanoparticles of silver by employing a lyotropic liquid crystal (LLC) template is described. Anisotropic silver particles are synthesised by reducing an appropriate amount of precursor silver nitrate using a mild reducing agent ascorbic acid in presence of a hexagonal LLC medium, without the aid of any external stabilising agents. In this synthesis, precursor concentration, type of the reducing agent and LLC phase are found to significantly influence the particle size and morphology. Either a decrease in the concentration of silver nitrate or a change in the reducing agent, from ascorbic acid to sodium borohydride in the same reaction medium, yielded quasi-spherical nanoparticles. Besides, replacing the hexagonal LLC medium with a lamellar phase during the synthesis using ascorbic acid also resulted in the formation of spherical particles in nanometre scale. As a comparison, gold nanoparticle synthesis is carried out in hexagonal and lamellar LLC phases. Similar to the observations made in the silver particle synthesis, branched anisotropic particles are formed in the hexagonal phase and quasi-spherical particles are produced in the lamellar phase. A possible growth mechanism for the formation of these particles based on the phase structure of the LLC medium is discussed.     

Synthesis of branched Man5 oligosaccharides and an unusual stereochemical observation

Branched mannopentaoses were synthesized through two routes. While assembly from the nonreducing end to the reducing end was more convergent with fewer intermediate steps, two diastereomers were obtained. On the other hand, synthesis from the reducing end to the nonreducing end yielded the mannopentaose with the desired stereochemistry as a single isomer. Our results suggest that it is still challenging to reliably predict stereochemical outcome of a glycosylation reaction. It is necessary to thoroughly characterize anomeric configurations of newly formed glycosidic linkages in complex oligosaccharide synthesis.     

Synthesis of N-(aminobutyl)-N-(ethylisoluminol) functionalized gold nanomaterials for chemiluminescent bio-probe

A novel strategy for the synthesis of CF-AuNMs by reducing HAuCl(4) with ABEI in aqueous solution at room temperature is reported. No additional stabilizing and reducing reagents are needed, and various morphologies of CF-AuNMs can be obtained. It could be used as bio-probe for bioassays.     

Tandem Reduction-Aldol Reactions Induced by Stryker's Reagent

The incorporation of tandem reactions into a synthetic plan is an important strategy to achieve an efficient synthesis. Consecutive transformations of a substrate in a one-pot synthesis multiplies the complexity of the product while reducing the overall number of steps in the synthetic pathway.     

Ultrasound-assisted rapid reduction of nitroaromatics to anilines using gallium metal

Abstract

The reduction of nitroaromatic compounds to anilines is widely used throughout organic synthesis. Typical methods of performing this transformation utilize hydrogenation over a pyrophoric catalyst or a finely divided reducing metal, which often affords heterogeneous mixtures that are difficult to purify. Herein, we report for the first time the use of gallium metal as a reducing agent in organic synthesis. The reaction proceeds under aerobic conditions and affords homogeneous mixtures for a convenient workup. Using this method, twelve anilines were obtained in 33% to quantitative yields with short reaction times of 10-60?minutes.     

Eu离子价态对Sr_2MgSi_2O_7:Eu发光特性的影响(英文)

分别在空气、还原气体、再空气、最后再在还原气体等气氛中通过四个步骤合成了Sr1.99MgSi2O7:Eu0.01.在空气中合成的样品呈现出Eu2+和Eu3+两种价态的发光特征峰,而在还原气体中合成的样品,只呈现出Eu2+一种价态的特征发光峰,并且有长余辉和两个热致发光带.但若样品直接在还原气氛下合成,则只呈现一个热致发光带.样品在空气中合成产生空穴陷阱,此陷阱在还原合成气氛下仍被保留,并与还原气体合成条件下产生的电子陷阱有所区别,最终导致两个热致发光带.     

Application of organic selenides and tellurides in organic synthesis

This paper describes the progress on the synthesis of organic selenides and tellurides and their application in organic synthesis.Low valent selenium and telluronium compounds having high reducing selectivity can be used to form carbon-hydrogen bonds as special reducing reagents.Telluronium ylides can react with aldehydes and ketones by Wittig-type condensation to produce (E)-configuration alkenes stereoselectively.α-Phenylselanyl arsonium ylides were prepared by transyl-idation reaction of arsonium ylides with phenylselanyl halides which can undergo Wittig-type reactions with carbonyl compounds to give (Z)-α-selanyl-α,β-unsaturated compounds with high stereoselectiv-ity.Zirconium,tin,boron,halogen,metal or hetero-atom were introduced in organoselenium and telluronium compounds as new difunctional group reagents.Under transition metal catalysis,the corresponding cross coupling reactions provide new methods of formation of carbon-carbon double bonds,which were used in the stereoselective synthesis of     

甲基萘磺酸系高效减水剂合成研究

减水剂在建筑混凝土中应用广泛,其中萘系高效减水剂具有减水率高,对混凝土的强度不产生有害影响且成本低的优点,在市场上占80%,其它各种减水剂由于减水率低的缺点在市场上仅占20%。实验以甲基萘油为原料,经过磺化、水解、缩合、中和四步反应,合成减水率高达16.8%的甲基萘磺酸系高效减水剂,并对合成中滴加硫酸温度、磺化温度、水解加水量、甲基萘与甲醛的物质量比等的各种影响因素作了进一步的探讨。     

Eu离子价态对Sr2MgSi207∶Eu发光特性的影响

分别在空气、还原气体、再空气、最后再在还原气体等气氛中通过四个步骤合成了Sr199MgSi2O7∶Eu0.01.在空气中合成的样品呈现出Eu2+和Eu3+两种价态的发光特征峰,而在还原气体中合成的样品,只呈现出Eu2+一种价态的特征发光峰,并且有长余辉和两个热致发光带.但若样品直接在还原气氛下合成,则只呈现一个热致发光带.样品在空气中合成产生空穴陷阱,此陷阱在还原合成气氛下仍被保留,并与还原气体合成条件下产生的电子陷阱有所区别,最终导致两个热致发光带.     

One-step synthesis of gold and silver hydrosols using poly(N-vinyl-2-pyrrolidone) as a reducing agent

Synthesis of gold and silver hydrosols was carried out in a one-step process by reduction of aqueous solutions of metal salts using poly(N-vinyl-2-pyrrolidone) (PVP). Both kinds of metal nanoparticles were obtained without the addition of any other reducing agent, at low temperatures and using water as the synthesis solvent. Shape, size, and optical properties of the particles could be tuned by changing the employed PVP/metal salt ratio. It is proposed that PVP acts as the reducing agent suffering a partial degradation during the nanoparticles synthesis. Two possible mechanisms are proposed to explain the reduction step: direct hydrogen abstraction induced by the metal ion and/or reducing action of macroradicals formed during degradation of the polymer. Initial formation of the macroradicals might be associated with the metal-accelerated decomposition of low amounts of peroxides present in the commercial polymer.     

Transformation of methane to synthesis gas over metal oxides without using catalyst

This article reviews a new developing method in the field of metal oxide reduction in chemical and metallurgical processes, which uses methane as a reducing agent. Commonly, coal is used as the reducing agent in the reduction of metal oxide and other inorganic materials; Metal producing factories are among the most intensive and concentrated source of greenhouse gases and other pollutants such as heavy metals, sulfur dioxide and fly ash. Thermodynamically, methane has a great reducing capability and can be activated to produce synthesis gas over a metal oxide as an oxygen donor. Metal oxide reduction and methane activation, two concurrent thermochemical processes, can be combined as an efficient and energy-saving process; nowadays this kind of technologies is of great importance. This new reduction process could improve energy efficiencies and significantly decrease greenhouse gas emission compared to the conventional process; furthermore, the produced gases are synthesis gas that is more valuable than methane. In this paper, thermodynamic studies and advantages of this promising method were discussed. The major aim of this article is to introduce methane as a best and environmentally friendly reducing agent at low temperature.     

Highly efficient synthesis of sialylglycopeptides overcoming unexpected aspartimide formation during activation of Fmoc-Asn(undecadisialyloligosaccharide)-OH

Oligosaccharyl Fmoc-asparagine in which amide nitrogen of the asparagine side chain attached to the anomeric position at the reducing end, is a versatile building block and has been used for various glycopeptide synthesis using Fmoc solid-phase peptide synthesis (SPPS). We found unexpected aspartimide formation between amide nitrogen at the reducing end and α-carboxyl acid of oligosaccharyl Fmoc-asparagine during activation of α-carboxyl acid and this side reaction resulted in low coupling yields of oligosaccharyl Fmoc-asparagine with peptide-resin. This aspartimide formed efficiently using conventional coupling reagents such as PyBOP and HATU, but DEPBT afforded little of the aspartimide derivative. Activation condition using DEPBT (3.0 equiv) and DIPEA (2.0 equiv) afforded excellent yield (97%) in coupling reaction between Fmoc-Asn(CHO)-OH and peptide-resin. Based on these results, we performed a synthesis of a sialylglycopeptide, HIV-gp120 (54-63) VVLLVN(CHO)VTENF, in high yield.     

A Short Synthesis of (S)-(+)-Siphonodiol

A short synthesis of the enantiomer of the polyacetylenic natural product siphonodiol is described. The synthesis is based on the strategy of taking advantage of the hidden symmetry of the target molecule and minimizing the use of protecting groups, thereby reducing the total number of steps and increasing the overall efficiency.     

A new ‘one-pot’ synthesis of hydrazides by reduction of hydrazones

A new, high-yielding methodology for reducing hydrazones to hydrazines is described, which allows the synthesis of different mono-, di- and trisubstituted hydrazines. Moreover, the reduction step can be followed by an in situ reaction with a carboxylic acid making possible a ‘one-pot’ synthesis of trisubstituted hydrazides. The method is relatively general and, in principle, suitable for industrial applications.     

Synthesis and characterization of fivefold twinned nanorods and right bipyramids of palladium

This Letter describes the first synthesis of fivefold twinned nanorods and right bipyramids of palladium in an aqueous solution, with ascorbic acid as a reducing agent and in the presence of bromide. Like the silver system, these two types of nanostructures are derived from multiple and single twinned seeds, respectively. The ascorbic acid, bromide, and reaction temperature all play important roles in the synthesis.     

An alternative efficient approach for the synthesis of Fingolimod hydrochloride

An efficient process for the synthesis of API Fingolimod Hydrochloride is presented. This proposed synthesis involves simple commercially available octanophenone as a starting material. The route is effective involving seven steps to achieve the target, thus reducing the cycle time, and is cost efficient by 50%. It is an immune modulating drug for the treatment of heart failure and arrhythmias.     

Silver Nanoparticles: Dependence of the Antimicrobial Activity on the Synthesis Conditions

Russian Journal of General Chemistry - Specific features of the synthesis of stable silver nanoparticles by chemical reduction with agents differing in the reducing ability were studied using...     

Cinnamomum tamala leaf extract-mediated green synthesis of Ag nanoparticles and their use in pyranopyrazles synthesis

A novel, biochemical, and eco-friendly method has been developed for the synthesis of Ag nanopar-ticles using an aqueous leaf extract of readily accessibleCinnamomum tamala as reducing and stabi-lizing agents. These Ag nanoparticles were used to catalyze the synthesis of pyranopyrazoles. The green nature and ease of recovery and reusability of the catalyst, together with high yields of prod-ucts, make this protocol attractive and useful.     

Synthesis and Characterization of Silver Nanoparticles Prepared with Honey: The Role of Carbohydrates

Silver nanoparticles were synthesized using honey at pH 5.0 and 10.0 using a rapid, low cost, and simple technique. The influence of the honey carbohydrates (glucose and fructose) in the synthesis was characterized. Moreover, the kinetic variables in the synthesis at room temperature and at pH 5.0 and 10.0 were analyzed by measuring surface plasmon resonance at 411?nm by absorption spectroscopy. Transmission electron microscopy, thermal gravimetric analysis, and differential thermal analysis were used to characterize the metal nanoparticles and the capping agents. The synthesized nanoparticles were obtained for the first time at pH 5.0. This fact allows evaluating the kinetics and reaction mechanism. The obtained nanoparticles were spherical, monodispersed, and smaller than 20?nm. The results show that glucose serves as a reducing and capping agent while fructose has a limited reducing effect.     

Opportunistic use of tetrachloroaurate photolysis in the generation of reductive species for the production of gold nanostructures

The photolysis of gold salts is rarely viewed as the initiation for gold nanoparticle (AuNP) formation. Yet, photolysis of AuCl(4)(-) generates chlorine atoms whose rich hydrogen transfer chemistry can readily generate strongly reducing radicals. Interesting precursors include hydrogen peroxide, 2-propanol, 1,4-cyclohexadiene and tetrahydrofuran; all of them yield strongly reducing radicals. Further, this group of substrates has been selected because of the innocuous and volatile nature of reagents and products, thus allowing a remarkably clean synthesis of gold nanostructures. In the case of H(2)O(2) the by-products are water and oxygen. The methodology reported here opens the door to particles that can be modified in situ or post-synthesis with custom surface covering without concern for chemical debris from the nanostructure synthesis.