DABCO-catalyzed synthesis of 3-substituted-3-hydroxyindolin-2-ones in aqueous media

An efficient and greener protocol for easy access to 3-susbstituted-3-hydroxy-2-oxindoles by the reaction with various substituted isatins and acetophenones is described. This protocol is widely applicable for a variety of isatins and acetophenones using water as a reaction media and 1,4-diazabicyclo[2.2.2]octane (DABCO) as catalyst with shorter reaction time and good to excellent yield of products.     

2-Aminoethanesulfonic acid: An efficient organocatalyst for green synthesis of spirooxindole dihydroquinazolinones and novel 1,2-(dihydroquinazolin-3(4H)isonicotinamides in water

Abstract

A facile and efficient one-pot procedure for the preparation of spirooxindole dihydroquinazolinone derivatives and new N-(4-oxo-2-phenyl-1,2-dihydroquinazolin-3(4H)-yl)isonicotinamides from reaction between isatoic anhydride, isoniazid and substituted aldehydes catalyzed by 2-aminoethanesulfonic acid (taurine) is describe. This new protocol has the advantages of environmental friendliness, good yields, and convenient operation. The reaction proceeds efficiently using water as green solvent and nontoxic catalysts that could be efficiently reused. Together with this simple workup procedure, use of the organocatalyst, and water as solvent without the need of column chromatographic purification, are the notable features of this methodology, which make this protocol a very efficient and green alternative to the traditional methods.     

Microwave assisted extraction of soy isoflavones

A fast and reliable analytical method using microwave assisted extraction has been developed. Several extraction solvents (methanol (MeOH) and ethanol (EtOH), 30-70% in water and water), temperatures (50-150 °C), extraction solvent volume, as well as the sample size (1.0-0.1 g) and extraction time (5-30 min) were studied for the optimization of the extraction protocol. The optimized extraction conditions for quantitative recoveries were: 0.5 g of sample, 50 °C, 20 min and 50% ethanol as extracting solvent. No degradation of the isoflavones was observed using the developed extraction protocol and a high reproducibility was achieved (>95%).     

Hard to remove water in cellulose fibers characterized by high resolution thermogravimetric analysis - methods development

A new method is applied to classify water, termed ‘hard-to-remove (HR) water’, in a cellulosic fiber and water system from an isothermal thermogravimetric analysis (TGA). The hard-to-remove (HR) water content is defined as the moisture ratio (g of water / g of dry sample) of the fiber-water system at the transition between the constant rate zone and the falling rate zone of evaporative change in mass. Specific experimental conditions have been defined for an appropriate measurement of the HR water content. The HR water content was correlated with measurable characteristics of cellulosic fibers including water retention value and freeness. The new TGA protocol can be performed on extremely small samples as a convenient and insightful characterization technique for cellulosic fibers.     

An efficient Pd(II)-(2-aminonicotinaldehyde) complex as complementary catalyst for the Suzuki-Miyaura coupling in water

An efficient new Pd(II)-(2-aminonicotinaldehyde)-catalyzed Suzuki-Miyaura coupling of the aryl halides (Br, Cl and I) and organoboronic acids at moderate temperature in water is described. Low catalyst loading, easy accessibility, being an air-stable catalyst, functional group compatibility, and water as the reaction medium are some of the key features of this synthetic method. This protocol is also applicable for gram scale.     

Highly Efficient C?N Bond Forming Reactions in Water Catalyzed by Copper(I) Iodide with Calix[4]arene Supported Amino Acid Ionic Liquid

A novel and effective protocol has been developed for the Ullmann‐type C? N coupling reaction catalyzed by calix[4]arene supported amino acid ionic liquid and copper(I) iodide in water under microwave irradiation condition. The protocol uses calix[4]arene supported amino acid ionic liquid as double function of the ligand and phase‐transfer catalyst, and shows good tolerance in good to excellent yields.     

Electron-Transfer Protocol for the Hydroxyalkenylation of Alkenes Using 1,2-Bis(phenylsulfonyl)ethylene

We report a protocol for alkene hydroxyalkenylation. Using a persulfate anion as a one-electron-oxidation reagent and 1,2-bis(phenylsulfonyl)ethylene as a radical acceptor in the presence of water, alkenes were converted into the corresponding 1-phenylsulfonyl-4-hydroxyalkenes in good to high yields. The hydroxyalkenylation process involves the nucleophilic hydroxylation of alkene radical cations to give β-hydroxyalkyl radicals, which, after a radical addition/β-elimination sequence, provide the products. We also report a photocatalytic protocol for alkoxyalkenylation.     

An efficient catalyst-free synthesis of novel benzo[a][1,3]oxazino[6,5-c]phenazine derivatives via one pot four-component domino protocol in water

A catalyst-free multicomponent reaction (MCR) capable of affording a wide range of novel benzo[a][1,3]oxazino[6,5-c]phenazine derivatives via one pot two-step domino protocol, in water is reported. Catalyst-free conditions along with green solvent system make the process ecofriendly as well as economical. Simple reaction conditions, easy work-up isolation, and purification of products are the significant advantages of the present protocol.     

Surfactant-type Brønsted acid catalyzed dehydrative nucleophilic substitutions of alcohols in water

A protocol for the dehydrative nucleophilic substitution of benzyl alcohols with a variety of carbon- and heteroatom-centered nucleophiles using dodecylbenzenesulfonic acid (DBSA) as a surfactant-type Br?nsted acid catalyst in water has been developed. The reaction system can be applied to the stereoselective C-glycosylation of 1-hydroxy sugars in water. [reaction: see text].     

Water-mediated catalyst preactivation: an efficient protocol for C-N cross-coupling reactions

A protocol for forming a highly active Pd(0) catalyst from Pd(OAc) 2, water, and biaryldialkylphosphine ligands has been developed. This protocol generates a catalyst system, which exhibits excellent reactivity and efficiency in the coupling of a variety of amides and anilines with aryl chlorides.     

Pd(OAc)2-Catalyzed Carbonylative Coupling of Aryl Iodide with Ortho-Haloamines in Water

The carbonylative cross coupling of aryl iodide with ortho-haloaniline to ortho-haloanilide using phosphine-free Pd(OAc)₂ catalyst in water as a reaction medium has been studied. The present protocol facilitated the reaction of o-haloanilines with a wide variety of hindered and functionalized aryl iodides, affording good yields of the desired products. The protocol was also extended for the synthesis of benzoxazoles through cyclization of ortho-haloanilide using Cu(acac)₂ catalyst.     

Remarkable synergism in methylimidazole-promoted decarboxylation of substituted cinnamic acid derivatives in basic water medium under microwave irradiation: a clean synthesis of hydroxylated (E)-stilbenes

A metal-free protocol for decarboxylation of substituted α-phenylcinnamic acid derivatives in aqueous media is developed, wherein a remarkable synergism between methylimidazole and aq NaHCO₃ in polyethylene glycol under microwave furnished the corresponding para/ortho hydroxylated (E)-stilbenes in a mild and efficient manner. The critical role of water in facilitating the decarboxylation imparts an interesting facet to the synthetic utility of water mediated organic transformations. The developed protocol provides a clean alternative to the hitherto indispensable multistep approaches involving toxic quinoline and a copper salt combination as the common decarboxylating agent.     

Biginelli reaction in aqueous medium: a greener and sustainable approach to substituted 3,4-dihydropyrimidin-2(1H)-ones

An environmentally benign aqueous Biginelli protocol for the synthesis of substituted 3,4-dihydropyrimidin-2(1H)-ones using polystyrenesulfonic acid (PSSA) as a catalyst has been achieved. These microwave-assisted reactions proceed efficiently in water in the absence of organic solvent, with simple filtration as the product isolation step.     

Visible light promoted formation of N─S bond by photocatalyst Eosin Y

A novel efficient protocol for the synthesis of 5-imino-1,2,4-thiadiazole motif in open air and visible light has been reported. The reaction involves Eosin Y as photocatalyst which is a cost-effective organic dye. The designed protocol represents a novel, mild, metal free, green strategy for the construction of 1,2,4-thiadiazole nucleus by intramolecular cyclization via N─S bond formation. The reaction has been carried out under visible light exposure in ethanol: water (4:1) mixture using 2-aminopyridine and isocyanate as reactants.     

General copper-catalyzed transformations of functional groups from arylboronic acids in water

A simple and general copper-catalyzed method has been developed for transformations of various functional groups (-I, -N(3), -SO(2)R, -OH, -NH(2), and -NO(2)) on aromatic rings from arylboronic acids in water under air. The protocol uses cheap and readily available inorganic salts (KI, NaN(3), NaSO(2)R, NaOH, NaNO(2)) and aqueous ammonia as the functional-group sources, simple Cu(2)O/NH(3) as the catalyst system, environmentally friendly water as the solvent, and oxygen in air as the oxidant. Importantly, the copper catalyst system in water was recyclable. This study should provide a useful strategy for interconversions of the functional groups on aromatic rings.     

Highly efficient one-pot synthesis of primary amides catalyzed by scandium(III) triflate under controlled MW

The present Letter highlights a versatile synthetic protocol for the one-pot synthesis of primary amides employing scandium(III) triflate as a catalyst in water under controlled MW. This methodology offers excellent yields in shorter reaction times with enhanced selectivity.     

Polystyrene sulfonic acid catalyzed greener synthesis of hydrazones in aqueous medium using microwaves

An environmentally benign aqueous protocol for the synthesis of cyclic, bi-cyclic, and heterocyclic hydrazones using polystyrene sulfonic acid (PSSA) as a catalyst has been developed; the simple reaction proceeds efficiently in water in the absence of any organic solvent under microwave irradiation and involves basic filtration as the product isolation step.     

Development of new DMAP-related organocatalysts for use in the Michael addition reaction of β-ketoesters in water

A general and efficient protocol for the Michael addition reactions of β-ketoesters in pure water has been developed. The reactions are successfully catalyzed by newly designed DMAP-related organocatalysts such as 4-(didecylamino)pyridine, and the desired Michael adducts are obtained in good to high yields     

Oxidation and sulfonation of cellulosics

Bleached hardwood (HW) kraft pulp and derived nanocellulosic structures were modified by a periodate oxidation followed by treatment with sodium bisulfite to yield the corresponding C2/3 sulfonates. The impact of this oxidative–reductive protocol on the chemical and physical properties of cellulose was evaluated by determining physical dimensions, functional groups, and their water absorbency properties. It was found that the water absorbency of cellulosic material can be enhanced by 8.0–199.0% with this oxidation/sulfonation protocol. Distinct differences were observed between sulfonated pulp fibers and nanocellulosic structures, with the latter exhibiting relatively higher water retention values (WRV).     

A powerful computational crystallography method to study ice polymorphism

Classical molecular dynamics (MD) simulations are employed as a tool to investigate structural properties of ice crystals under several temperature and pressure conditions. All ice crystal phases are analyzed by means of a computational protocol based on a clustering approach following standard MD simulations. The MD simulations are performed by using a recently published classical interaction potential for oxygen and hydrogen in bulk water, derived from neutron scattering data, able to successfully describe complex phenomena such as proton hopping and bond formation/breaking. The present study demonstrates the ability of the interaction potential model to well describe most ice structures found in the phase diagram of water and to estimate the relative stability of 16 known phases through a cluster analysis of simulated powder diagrams of polymorphs obtained from MD simulations. The proposed computational protocol is suited for automated crystal structure identification.