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The extraction and adsorption characteristics of three phenolic aldehydes with high physicochemical similarity in lignocellulosic biomass hydrolyzate, which are fermentation inhibitors, were investigated. The extraction process considered both physical extraction with two organic solvents and reactive extraction with five basic extractants. In physical extraction, n-hexane was found to be the most suitable organic solvent for selectively separating 4-hydroxybenzaldehyde from the three phenolic aldehydes, and in reactive extraction, trioctylphosphine oxide was identified as the most suitable basic extractant for the selective separation of syringaldehyde. In the adsorption process, various neutral polymer resins and anion-exchange polymer resins were employed. Among them, the neutral polymer resin XAD16 was found to be the most suitable for selectively separating 4-hydroxybenzaldehyde. To efficiently separate and concentrate the three phenolic aldehydes with equal mass percentages, a proposed five-step fractionation process included the aforementioned extraction and adsorption techniques. By implementing n-hexane-based physical extraction in step 4 and NaOH solution-based back-extraction in step 5 of the fractionation process, the purities of 4-hydroxybenzaldehyde, vanillin, and syringaldehyde in the final solution increased from their initial 33.3% each to 67.6%, 69.8%, and 76.4%, respectively, at a volume ratio of the aqueous phase to the organic phase of 1:15. [ABSTRACT FROM AUTHOR]

The chemical stability of zeolitic imidazolate framework-8 (ZIF-8) in water, acid, base and organic solvent has been widely investigated. However, whether it is stable in aldehydes, which are common reactants, has rarely been considered. Herein, the partial or whole dissolution of ZIF-8 with 50 nm and 1000 nm sizes was observed in crotonaldehyde under air conditions. More importantly, the residual ZIF-8 gradually evolved from the original rhombic dodecahedra into a new octahedron morphology and still preserved the ZIF-8 phase structure. A series of experiments revealed that the essence of ZIF-8 degradation in crotonaldehyde is the presence of H+, derived from the autoxidation of crotonaldehyde exposing in the air to the corresponding acids. H+ could preferentially attack the Zn–N coordination bond located at the {211} edge and {111} vertices with {110} facet shrinkage of the rhombic dodecahedra, leading to the morphological reconstruction of ZIF-8. A further dynamic track showed that the dissolved ratio of ZIF-8 highly depended on the acidic value of crotonaldehyde, temperature and contact time. The dissolution process followed a shrinking core model and was controlled by the diffusion of the H+ step. [ABSTRACT FROM AUTHOR]

A series of modified polysaccharide polymers were prepared via a solvent-free synthesis involving heterogeneous Schiff base reaction of carboxymethyl chitosan (CMCS) with diverse aldehydes: hexanal, citral, benzaldehyde, 4-methoxybenzaldehyde, 4-chlorobenzaldehyde, and trans-cinnamaldehyde. The prepared CMCS derivatives were extensively studied in terms of their physicochemical, mechanical and morphologic properties. The presented solvent-free method allows multicycle preparation of the desired products. The properties of products prepared by the new method and traditional solvent-based synthesis were compared. The new process meets the essential requirements of green chemistry by diminishing waste products and eliminating organic solvents, while maximizing the use of the involved reagents. Being easily adjusted to suit various substituents, this method offers a potential platform for a formation of new materials and promotes environmentally friendly industrial practices. [ABSTRACT FROM AUTHOR]

A catalyst‐free tandem reaction was developed for the clean synthesis of spiro[2,3‐dihydrofuran‐3,3'‐oxindole] derivatives from 2‐(2‐oxoindolin‐3‐yl)malononitriles and aldehydes in water. This method has an extensive substrate scope. The targeted products were easily isolated by filtration in high yields and excellent diastereoselectivities. The reaction also features numerous advantages, including step/atom economy, both catalyst and additive‐free, no organic solvents, simple work‐up, short reaction times, and environmentally friendly conditions. The present strategy utilizes simple conditions, demonstrating the potential application in the synthesis of pharmaceuticals and biologically active compounds. [ABSTRACT FROM AUTHOR]

Vegetable oils and their derivatives are of great interest because of their abundance and renewability. This paper prepares nonanal (N) and methyl 9‐oxonanoate (M) from methyl epoxystearate (ME) with WO3∙0.33H2O, WO3∙H2O, and WO3∙2H2O as catalysts and H2O2 as the oxidant without the use of organic solvent. The reaction temperature, catalyst amount, H2O2 amount, and reaction time effects on ME conversion and N/M yield are investigated. The results show that WO3∙H2O has the best catalytic performance. The optimal reaction conditions are: reaction temperature 60 °C, reaction time 40 min, ME/H2O2/WO3∙H2O molar ratio 1/1.2/0.4, under which the ME conversion and N/M yield reach 95% and 70%, respectively. WO3∙nH2O reacts with H2O2 to form soluble tungsten anions, resulting in severe tungsten loss. Al‐MCM‐41 materials with different silicon to aluminum molar ratios are added to the reaction system as adsorbents to recover the catalyst by effective adsorption of tungsten anions. The adsorption performance improves as the Si/Al ratio decreases, however, the ME conversion and N/M yield decrease. Thus, 50 is the most suitable Si/Al ratio. The ME conversion and N/M yield can still reach 90% and 60% after four times of use. Practical applications: The nonanal has a natural fragrance and can be used in the cosmetic industry as well as in the preparation of bio‐based surfactants. The methyl 9‐oxonanoate can be converted into polymer monomers by hydrogenation or amination. The results show that WO3∙nH2O has good catalytic activity, and a satisfying yield of aldehyde products is obtained under mild reaction conditions. [ABSTRACT FROM AUTHOR]

The use of fungal aryl‐alcohol oxidases in biocatalysis is still modest, despite their advantageous capability to produce valuable aldehydes via oxidation of the respective alcohols without the need for costly external cofactors. For biocatalytic application, enzyme stability in the presence of organic solvents used for substrate solubilization has to be investigated, and process limitations due to low oxygen supply and the accumulation of the by‐product H2O2 must be addressed. In this study, we showed that the aryl‐alcohol oxidase PeAAO2 from Pleurotus eryngii P34 remained active and stable in the presence of up to 30% (v/v) various organic solvents and up to 500 mM H2O2. The potential of this biocatalyst was explored based on conversion of piperonyl alcohol to the fragrance compound piperonal. After reaction optimization, product titers of up to 245 mM were achieved within 3 h. Addition of catalase was imperative to re‐introduce O2 as co‐substrate into the reaction, thereby diminishing oxygen limitation. On a preparative scale, space‐time‐yield of 9.5 g/l/h was achieved and 244.6 mg piperonal (85% yield) with >99% purity were isolated via simple crystallization from n‐hexane extract. Under optimized reaction conditions four other substrates, cumic alcohol, 2‐thiophenemethanol, trans,trans‐2,4‐heptadienol and trans‐2‐cis‐6‐nonadienol, at concentrations of up to 300 mM were converted to the corresponding aldehydes within 20 h. Our results demonstrate that PeAAO2 is a versatile and promising biocatalyst for the production of valuable aldehydes. [ABSTRACT FROM AUTHOR]

• La 1-x K x MnO 3 perovskites synthesized by electrospinning method are reported. • La 1-x K x MnO 3 exhibits a nanofiber tube structure and evolved (1 1 0) lattice plane. • La 0.95 K 0.05 MnO 3 shows above 93 % conversion and selectivity for the reaction, even is conducted at 50 °C, for 3 h. • DFT calculations verifies that the O–O bond can be automatically ruptured if O 2 is adsorbed on the (1 1 0) lattice plane of material. • La 1-x K x MnO 3 is applicable to various alcohols and the reaction nature is discussed. Aerobic oxidation of alcohols to aldehydes is a green and prospective route to synthesize fine chemicals, but the high activation barrier and low solubility in organic solvents of O 2 make this technology a challenge. Herein, we report an electrospinning synthesis of K doped LaMnO 3 perovskite (La 1-x K x MnO 3), with nanofiber tube (NFT) structure, for efficient liquid-phase aerobic oxidation of alcohols to aldehydes at low temperature. The NFT structure improves the capacity of material to capture O 2 , the generated oxygen vacancy, caused by K doping, increases the sites to adsorb O 2 , and the evolved (1 1 0) lattice plane promotes the ability to activate O 2. The optimized La 0.95 K 0.05 MnO 3 shows above 93 % conversion and selectivity, even is conducted at 50 °C, for 3 h, which is the lowest temperature reported for aerobic oxidation of alcohols using noble metal-free catalysts. Simulated calculations suggest that the O-O bond can be automatically ruptured if O 2 is adsorbed on the (1 1 0) lattice plane of the material. [ABSTRACT FROM AUTHOR]

Nanostructured SiO2–H2SO4 as an efficient and nano catalyst for one-pot synthesis of phtahalazines via three-component condensation of an aromatic or aliphatic aldehyde, malononitrile and 5-amino-2,3-dihydro-phthalazine-1,4-dione. Nanostructured SiO2–H2SO4 was synthesized and characterized via FT-IR and SEM techniques. It is rapid and efficient catalyst for one-pot synthesis of the biologically important 3,9-diamino-5,10-dioxo-1-aryl-5,10-dihydropyrazolo[1,2-b]phthalazine-2-carbonitrile derivatives. The significant features of this methodology are nontoxic catalyst, short reaction time (10 min), recyclability, low catalyst loading, green organic solvent (ethanol), and avoiding tedious purification step. [ABSTRACT FROM AUTHOR]

The synthesis of 2-amino-4H-chromenes through one-pot multicomponent reactions has received great attention due to the high atom efficiency and the broad bioactivities of the products. Here, the catalytic performances of a series of functional ionic liquids towards this type of reaction were investigated and the results showed that the ionic liquid, choline acetate ([Choline][Ac]), could efficiently promote this reactions under room temperature without the necessary of organic solvents. The reaction is easy to be conducted and the following work-up procedures are very simple. The pure products can be obtained through extraction and washing procedures, no column separation procedures are needed. Intriguingly, this reaction system can be easily scaled up to multi-gram, suggesting its perspective in industrial applications. In addition, the ionic liquid [Choline][Ac] can be easily prepared from cheap and biocompatible materials, and it can be feasibly recycled and reutilized for at least five cycles. Various aldehydes, malononitrile and activated phenols could be converted to the corresponding 2-amino-4H-chromenes with good to excellent isolated yields under the catalysis of choline acetate at room temperature. [ABSTRACT FROM AUTHOR]

Acetalization of glycerol with acetone (1 : 5) at 60 °C catalyzed by A‐46 (10 wt %) under nitrogen (N2) afforded 63 % solketal 1 a in just 15 min. Subsequently, acetalization of glycerol and bio‐based aldehydes i. e. acetaldehyde, isobutyraldehyde, n‐heptaldehyde, p‐anisaldehyde and benzaldehyde were investigated under optimized reaction conditions. The conversion and selectivity of this reaction was found to be affected by structure of aldehydes employed. Excellent conversion of 97 and 99 % were obtained using acetaldehyde and isobutyraldehyde, respectively while longer chain or aromatic aldehyde gave poor conversion between 17 and 36 %. Aldehyde with branching or aromatic ring gave better selectivity towards 6‐membered ring acetal b at the expense of conversion: p‐anisaldehyde > benzaldehyde>isobutyraldehyde>acetaldehyde>n‐heptaldehyde. Conversely, organic solvent gave adverse effects to both conversion and selectivity towards b. Optimized acetalization of glycerol/benzaldehyde was also studied. A‐46 has shown excellent stability and reactivity with no significant loss of catalytic activity in 10 subsequent runs. [ABSTRACT FROM AUTHOR]

A peptide reactivity assay with an activation component was developed for use in screening chemicals for skin sensitization potential. A horseradish peroxidase-hydrogen peroxide (HRP/P) oxidation system was incorporated into the assay for characterizing reactivity of hapten and pre-/prohapten sensitizers. The assay, named the Peroxidase Peptide Reactivity Assay (PPRA) had a predictive accuracy of 83% (relative to the local lymph node assay) with the original protocol and prediction model. However, apparent false positives attributed to cysteine depletion at relatively high chemical concentrations and, for some chemicals expected to react with the −NH2 group of lysine, little to no depletion of the lysine peptide were observed. To improve the PPRA, cysteine peptide reactions with and without HRP/P were modified by increasing the number of test concentrations and refining their range. In addition, removal of DL-dithiothreitol from the reaction without HRP/P increased cysteine depletion and improved detection of reactive aldehydes and thiazolines without compromising the assay's ability to detect prohaptens. Modification of the lysine reaction mixture by changing the buffer from 0.1 M ammonium acetate buffer (pH 10.2) to 0.1 M phosphate buffer (pH 7.4) and increasing the level of organic solvent from 1% to 25% resulted in increased lysine depletion for known lysine reactive chemicals. Refinement of the prediction model improved the sensitivity, specificity, and accuracy for hazard identification. These changes resulted in significant improvement of the PPRA making it is a reliable method for predicting the skin sensitization potential of all chemicals, including pre-/prohaptens and directly reactive haptens. [ABSTRACT FROM AUTHOR]

The results of 60 years' research into the mechanisms of olefin oxidation catalyzed by palladium complexes (Wacker oxidation) are analyzed. The concepts of the mechanisms of related oxidative carboxylations (Moiseev reaction) and alkoxylations are discussed. This review considers the regularities of processes in aqueous organic solvents; the problems of regio- and stereoselectivity of reactions; and the role of co-catalysts, oxidants, and ligands, including asymmetric catalysis. The effect of transition from anionic (or neutral) to cationic palladium chloride complexes in water or aqueous organic media on the mechanism of olefin oxidation is discussed in detail. [ABSTRACT FROM AUTHOR]

The TEMPO‐catalyzed oxidation of alcohols to aldehydes has emerged to one of the most widely applied methodologies for such transformations. Advantages are the utilization of sodium hypochlorite, a component of household bleach, as an oxidation agent and the use of water as a co‐solvent. However, a major drawback of this method is the often occurring strict limitation to use dichloromethane as an organic solvent in a biphasic reaction medium with water. Previous studies show that dichloromethane cannot easily be substituted because a decrease of selectivity or inhibition of the reaction is observed by using alternative organic solvents. Thus, up to now, only a few examples are known in which after a tedious optimization of the reaction dichloromethane could be replaced. In order to overcome the current limitations, we were interested in finding a TEMPO‐oxidation method in alternative organic solvents, which is applicable for various alcohol oxidations. As a result, we found a method for N‐oxyl radical‐catalyzed oxidation using sodium hypochlorite as an oxidation agent in nitriles as an organic solvent component instead of dichloromethane. Besides the oxidation of aromatic primary alcohols also aliphatic primary alcohols, secondary alcohols as well as dialcohols were successfully converted when using this method, showing high selectivity towards the carbonyl compound and low amounts of the acid side‐product. [ABSTRACT FROM AUTHOR]

A protocol for selectively oxidizing aldehyde over hydroxymethyl group is developed, using biomass starch protected gold nanoparticles (NPs) as catalyst. The Au NPs show high selectivity that aldehyde is oxidized into carboxylic acid while alcoholic hydroxyl group stays intact in selective oxidation of 4-(hydroxymethyl)-benzaldehyde. The heterogeneous catalysis system is composed of soluble catalysts and insoluble substrate. The gold catalyst is prepared, preserved and applied for catalytic oxidation all in water. After reaction conditions are optimized, H2O2 is found to be the best oxidizing agent with complete conversion. Besides, the gold catalyst displays good versitility for aldehyde derivatives. After reaction completes, organic components are extracted by organic solvent and gold NPs in water are separated and recycled. [ABSTRACT FROM AUTHOR]

Aldehydes are carbonyl compounds that are highly reactive and extensively abundant in nature. Aldehydes are biomarkers for oxidative stress-linked disorders since they are formed as a result of oxidative processes. Aldehydes may occur in food as a result of food processing or degradation, and their level has been utilized as a guide of food quality level. Therefore, aldehydes are identified in biological and food samples as illness indicators and as by-products of food manufacturing, respectively. Among analytical methodologies, chromatographic methods are the most used for the simultaneous determination of various aldehydes. However, chromatographic methods consume a lot of harmful organic solvents and reagents. Hence, herein, a comprehensive greenness evaluation of the reported chromatographic methods for aldehydes has been conducted using AGREE—Analytical GREEnness Metric. This review helps to recommend those methods that are eco-friendly to be further used for the assay of aldehydes in versatile samples. [Display omitted] • AGREE was applied to assess the greenness of the reported methods for aldehydes determination. • A comparison was conducted based on the 12 input variables of AGREE. • Different derivatization agents for aldehydes and their analytical application were discussed. • Weaknesses and strength points were highlighted within the framework of greenness. • Recommendations were emphasized for empowering analytical methods' greenness. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Practical one-pot reaction for preparation of 5-substituted-1 H -tetrazoles. • Without using high boiling point or volatile organic solvents in the reaction. • Easy reaction set-up and multigram scale. Abstract A series of 5-substituted-1 H -tetrazoles have been efficiently synthesized in moderate to excellent yields (68–90%) under mild reaction conditions by combining aryl aldehydes, hydroxylamine hydrochloride with sodium azide in the presence of catalytic amount of Cu(OAc) 2 in deep eutectic solvent (DES). The new synthetic method has many advantages, such as high conversion, green reaction medium, easy work-up, low cost, and environment friendly. [ABSTRACT FROM AUTHOR]

The new type of ‘on-solvent’ multicomponent reaction was found: transformation of benzaldehydes, malononitrile and 4-hydroxy-6-methylpyridin-2(1H)-one in the presence of sodium acetate as catalyst in a small amount of ethanol results in formation of substituted 2-amino-7-methyl-5-oxo-4-phenyl-5,6-dihydro-4H-pyrano[3,2-c]pyridine-3-carbonitriles in excellent 92-99% yields. This novel ‘one-pot’ process opens an efficient and convenient way to functionalize pyrano[3,2-c]pyridine systems, which are promising compounds for different biomedical applications. [ABSTRACT FROM AUTHOR]

The measurement of α-dicarbonyls and other degradation products of sugars has become important in view of their toxicity. Although there are several methods used for their analysis, most require long reaction times to form UV absorbing or fluorescent derivatives and the nonpolar nature of commonly used derivatives necessitates relatively high concentrations of organic solvents for elution in reverse phase liquid chromatography. The present method describes the use of Girard-T reagent in a simple, one step derivatization of α-dicarbonyls and conjugated aldehydes and analysis using ion-pair reverse phase liquid chromatography. The limit of detection was in the range of 0.06-0.09 μM (4-12 ng/mL) for glyoxal, methylglyoxal, 3-deoxyglucosone and 5-hydroxymethylfurfural with good linear response and reproducibility using UV detection. The hydrazone derivatives were stable for several days in solution. The method was used to study degradation of several sugars and quantification of the target α-dicarbonyls and 5-hydroxymethylfurfural in several soft drinks. [ABSTRACT FROM AUTHOR]

The dynamic exchange of enamines from secondary amines and enolizable aldehydes has been demonstrated in organic solvents. The enamine exchange with amines was efficiently catalyzed by Bi(OTf)3 and Sc(OTf)3 (2 mol %) and the equilibria (60 m m) could be attained within hours at room temperature. The formed dynamic covalent systems displayed high stabilities in basic environment with <2 % by-product formation within one week after complete equilibration. This study expands the scope of dynamic C−N bonds from imine chemistry to enamines, enabling further dynamic methodologies in exploration of this important class of structures in systems chemistry. [ABSTRACT FROM AUTHOR]

Oxidation of aldehydes to carboxylic acids is a major reaction. Conventionally, this reaction is carried out with oxidants and metal catalysts, thus producing unwanted metal waste. Recently, aqueous media have been used as an alternative for toxic organic solvents. Here, we tested the clathrate-structured, neutral hydrogen peroxide adduct 4NaSO·2HO·NaCl for the oxidation of aldehydes to acids in aqueous solution. We found that various aromatic, heteroaromatic and aliphatic aldehydes were selectively oxidized to corresponding acids in 70-98% yields. This simple acid-base treatment allows to separate easily the acid product in high purity without any organic solvent. Moreover, the adduct is produced using 25% HO, with inexpensive sodium sulphate, NaSO, and sodium chloride, NaCl. The adduct is a non-toxic white crystalline solid, readily soluble in water, and easy to handle. [ABSTRACT FROM AUTHOR]

Pyrrolidine-derived organocatalysts have been tested in two types of α-heterofunctionalization reactions in aqueous media or under solvent-free ball-milling conditions. The best results in terms of both activity and enantioselectivity were obtained with O-silylated 4-hydroxyproline derivatives in the α-aminoxylation reaction between n-butyraldehyde and nitrosobenzene (83 % yield in water, 86 % yield by ball milling and ee > 99 %). A very good yield (82 %) and excellent optical purity (ee > 99 %) were also achieved in the α-hydrazination reaction of 3-phenylpropanal with dibenzyl azodicarboxylate by the ball-milling technique [ABSTRACT FROM AUTHOR]

[RhCl(COD)] 2 in combination with a water soluble sulphonated pyridyl-triazolyl N,N -bidentate ligand efficiently catalyzes styrene and 1-hexene hydroformylation in water/organic solvent biphasic systems. The catalyst displays a good activity affording mixtures of linear and branched aldehydes with complete chemoselectivity. The aqueous catalytic phase may be recycled four times giving complete substrate conversion by 18 h. Mercury-poisoning experiments and transmission electron microscopy indicate that, after the first catalytic run, rhodium is present in the aqueous phase in nanoparticle form. [ABSTRACT FROM AUTHOR]

In this article, the first use of silicotungstic acid (HSiWO) as a catalyst for the synthesis of octahydroxanthene-1,8-diones by the reaction of 5,5-dimethylcyclohexane-1,3-dione (dimedone) with various aldehydes under thermal solvent-free conditions is described. The obtained results showed that the catalyst has a high catalytic activity, and the desired products were obtained in high yields. Moreover, the catalyst was found to be reusable, and a considerable catalytic activity still could be achieved after the fifth run. Easy work-up and avoidance of using harmful organic solvents are the other advantages of this simple procedure. [ABSTRACT FROM AUTHOR]

The new multicomponent reaction comprises the triethylamine catalyzed assembling of salicylaldehydes, 2-aminoprop- 1-ene-1,1,3-tricarbonitrile and 3-methyl-2-pyrazolin-5-one in small amount of propanol, which affords substituted 2,4-diamino-5-(5-hydroxy-3-methyl-1H-pyrazol-4-yl)-5Hchromeno[2,3-b]pyridine-3-carbonitriles in 63–98% yields. This process is in agreement with PASE principles and opens the way to new chromeno[2,3-b]pyridine scaffold containing 3-methyl-2-pyrazolin-5-one fragment, which is promising for various biomedical applications. [ABSTRACT FROM AUTHOR]

Copper(I) oxide nanoparticles (CONPs) catalyze multicomponent coupling/cycloisomerization reactions between various 2-hydroxybenzaldehydes, secondary amines, and nonactivated alkynes to give 2,3-disubstituted 1-benzofurans. All reactions are carried out under solvent- and ligand-free conditions at 100 °C in air. The combination of copper-catalyzed C-H activation and an Oannulation process is essential for this transformation. This methodology provides rapid access to substituted 1-benzofurans in good to excellent yields with high atom economy and high catalytic efficiency. This procedure eliminates the need for propargylamine derivatives, uncyclized intermediates that make purification difficult. The CONPs and tetrabutylammonium bromide were reused successfully for up to five times. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(vinyl alcohol) has been functionalized with aldehydes in tetrahydrofuran (THF) with a good control of the grafting. A wide library of poly(vinyl acetals) could be obtained in order to study some structure/property correlations. The influence of the aldehyde nature on the functionalization rates has been studied, in particular for optical properties by measurement of the shininess for further applications in the cosmetic field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40677. [ABSTRACT FROM AUTHOR]

Although single- and multi-step biocatalytic approaches show persuasive advantages for the synthesis of especially chiral compounds (e.g. high chemo- and stereoselectivity), their application often suffers from low substrate loads and hence low space-time-yields. We herein present a synthetic cascade approach in which lyophilised, recombinant whole cells are applied in micro-aqueous reaction systems yielding extremely high space-time-yields. As an example we investigated the two-step synthesis of 1-phenylpropane- 1,2-diol starting from cheap aldehydes and achieved high selectivities (ee/de > 99%) and high product concentrations. The new concept of running biocatalytic cascades in a mixture of high substrate loads and organic solvents under addition of small amounts of highly concentrated buffer is not only very easyto- apply, but also exhibits several economic and ecologic advantages. On the one hand the usage of whole, lyophilised cells circumvents time-consuming enzyme purification as well as addition of expensive cofactors (here ThDP and NADPH). Additionally, catalyst and product workup is facilitated by the application of organic solvents (here MTBE). On the other hand, the employment of whole cells very effectively circumvents stability problems of biocatalysts in unconventional media enabling the addition of extremely high substrate loads (up to 500 mM in our example) and is therefore an easy and effective approach for multi-step biocatalysis. After optimisation, the combination of a carboligation step followed by a second oxidoreduction step with whole cell catalysts afforded an efficient two-step cascade for the production of 1-phenylpropane-1,2-diol with space-time yields up to 327 g L-1 d-1 and an E-factor of 21.3 kgwaste kgproduct -1. [ABSTRACT FROM AUTHOR]

The scalable pinacol coupling reaction is realized utilizing the inorganic electride [Ca2N]+e-- as an electron donor in organic solvents. The bond cleavages of the [Ca2N]+ layers by methanol play a vital role in transferring anionic electrons to electrophilic aldehydes, accompanying the formation of Ca(OMe)2 and ammonia. [ABSTRACT FROM AUTHOR]

A simple, efficient, eco-friendly, and cost-effective method has been developed for the synthesis of symmetrical bisthioglycolic acid derivatives by a one-pot reaction of aldehydes or ketones with thioglycolic acid under solvent- and catalyst-free conditions in excellent yields (87–97%). The advantages of this novel protocol include the excellent yields, operational simplicity, short reaction times, and the avoidance of the use of organic solvents and catalysts. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present work is to develop a new tanning process (that we call Wet Bright) that produces perfectly white leather and meets all the requirements for automotive leather. What is obtained through this new process is a leather free of chromium, aldehydes, aldehyde precursors and organic solvents. This new system consists of the application of Tanfor T™ system (from Kemira), which is safe for both humans and the environment and is not classified as hazardous. When compared to existing traditional processes, namely chrome tanned leather (Wet-Blue) and aldehyde tanned leather (Wet-White), there are economic and environmental advantages resulting from the use of this new system. In this vein, this new process results in significant COD reductions. More specifically, the new system is an environmentally-friendly process since it reduces COD by 60%, suspended solids by 61%, and nitrogen by 65% compared with chromium tannage. In addition, Wet-Bright leathers present a reduction of 43% in volatile compounds versus Wet-White and a reduction of 8% versus Wet-Blue. And most importantly, wastewaters from this new system do not contain chromium. [Copyright &y& Elsevier]

Abstract: This is a report of an innovative, one-pot, catalyst-free, four-component synthesis of octahydro-imidazo[1,2-a]quinolin-6-ones from aromatic aldehydes, cyclic 1,3-diones, diamines, and nitro ketene dithioacetal in stoichiometric melt conditions. The protocol avoids the use of expensive catalysts, toxic organic solvents and anhydrous conditions, and affords potentially bioactive compounds in excellent to high yields. [Copyright &y& Elsevier]

Hollow fiber solvent bar microextraction coupled with high-performance liquid chromatography was developed for the preconcentration and determination of active ingredients inRadix Salvia miltiorrhiza. These ingredients include dihydrotanshinone I, cryptotanshinone, tanshinone I, tanshinone IIA, salvianolic acid B, danshensu, and protocatechuic aldehyde. To evaluate the technique, seven compounds of varying polarity were used as model analytes, and a polyvinylidene fluoride hollow fiber (1.0 cm) with octanol (2 µL) was used as microextraction bar. The extraction conditions, including the identity of the hollow fiber, organic solvent, pH, salt addition, agitation speed, extraction time, and volume, were investigated and optimized. The extraction mechanism was analyzed and verified. The two main parameters, extraction recovery and enrichment factor, were obtained. Under the most favorable conditions, the enrichment factors of the analytes were 0.7–612, the limits of detection were below 1.11 ng mL−1, and the recoveries were between 95.4% and 101.3%. Thus, hollow fiber solvent bar microextraction is simple, rapid, and practical with a wide range of potential applications. [ABSTRACT FROM AUTHOR]

An efficient Hantzsch synthesis of various substituted 1,4-dihydropyridines from an aldehyde, a β-dicarbonyl compound and ammonium acetate using p-toluenesulfonic acid in a solvent-free condition in the absence of any other co-catalyst is described. The process is simple and environmentally benign and the catalyst is commercially available and inexpensive. This method has the advantages of excellent yield (80-96%) and short reaction time (5-20 min.). Irradiation of a typical 1,4-dihydropyridine leads to the corresponding pyridine. [ABSTRACT FROM AUTHOR]

Highlights: [•] Efficient metal-mediated Reformatsky reaction of bromodifluoromethyl ketones and aldehydes was investigated. [•] Water is suitable solvent for this transformation. [•] The reactions of ketones and aldehydes could tolerate a broad range of functional groups. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fluorination of α-bromoketones undergoes efficiently with TBAF·3H2O in water. [•] Water as a reaction medium was superior to organic solvents for the fluorination. [•] Condensation of α-fluoroketones with aldehydes affords α-fluoroenones. [ABSTRACT FROM AUTHOR]

A one-pot method has been developed for the oxidative cleavage of internal alkenes into aldehydes by using 0.5 mol % of the nonheme iron complex [Fe(OTf)2(mix-bpbp)] (bpbp= N, N′-bis(2-picolyl)-2,2′-bipyrrolidine) as catalyst and 1.5 equivalents of hydrogen peroxide and 1 equivalent of sodium periodate as oxidants. A mixture of diastereomers of the chiral bpbp ligand can be used, thereby omitting the need for resolution of its optically active components. The cleavage reaction can be performed in one pot within 20 h and under ambient conditions. Addition of water after the epoxidation, acidification and subsequent pH neutralization are crucial to perform the epoxidation, hydrolysis, and subsequent diol cleavage in one pot. High aldehyde yields can be obtained for the cleavage of internal aliphatic double bonds with cis and trans configuration (86-98 %) and unsaturated fatty acids and esters (69-96 %). Good aldehyde yields are obtained in reactions of trisubstituted and terminal alkenes (62-63 %). The products can be easily isolated by a simple extraction step with an organic solvent. The presented protocol involves a lower catalyst loading than conventional methods based on Ru or Os. Also, hydrogen peroxide can be used as the oxidant in this case, which is often disproportionated by second- and third-row metals. By using only mild oxidants, overoxidation of the aldehyde to the carboxylic acid is prevented. [ABSTRACT FROM AUTHOR]

Microwave-assisted synthesis of 3,4-dihydropyrimidin-2-thiones via Biginelli reaction from aldehydes, acetoacetates, and thiourea in the presence of iodine under solvent-free conditions has been accomplished in good yields and purity without chromatographic separation. [ABSTRACT FROM PUBLISHER]

A novel one-pot synthesis of 1,2-dihydro-1-arylnaphtho[1,2-e][1,3]oxazine-3-ones by condensation of a variety of aldehydes with β-naphthol and urea or thiourea in the presence of wet cyanuric chloride under solvent-free condition has been described. High yields, simple procedure, easy workup, short reaction times, and avoiding the use of organic solvent are the advantages of this green methodology. [ABSTRACT FROM AUTHOR]

Scandium triflate efficiently promotes a one-pot, three-component condensation of aldehydes, malononitrile, and thiophenols to produce highly substituted pyridines in good yields. This reaction does not involve any hazardous organic solvent and toxic catalyst. [ABSTRACT FROM AUTHOR]

A facile and convenient procedure for the synthesis of 4H-pyrans from aldehydes, malononitrile, and ethyl acetoacetate/acetylacetone and also synthesis of 4H-pyrano[2,3-c]pyrazoles from three-component condensation of aldehydes, malononitrile, and pyrazolone or four-component condensation of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine monohydrate using [bmim]OH as task-specific ionic liquid has been described. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium. [ABSTRACT FROM AUTHOR]

An efficient and convenient method for the preparation of 3-benzylquinazolin-4(1H)-one derivatives under solvent-free and catalyst-free conditions by the reaction of isatoic anhydride, benzylamine, and aromatic aldehydes was reported. In reported papers, ammonia water, ammonium salt, and aromatic amine were often used to synthesize quinazolin-4(1H)-one derivative, but benzylamine was seldom used in this synthesis. This article offers a green method for the synthesis of 3-benzylquinazolin-4(1H)-one derivative used benzylamine as starting material. This methodology has the advantages of short reaction time, mild reaction conditions, easy work-up, and environmental friendliness. [ABSTRACT FROM AUTHOR]

An eco-friendly, simple, and effective protocol is developedforthe synthesis of various multisubstituted 2-aminothiophenes. In thepresence of a catalytic amount of ZnO (5 mol %), ketones oraldehydes, malononitrile and elemental sulfur were converted to thecorresponding 2-aminothiophene derivatives in moderate to high yields(27%–70%) under solvent-free conditions at 100 °C. Zincoxide as an efficient, readily available, and reusable catalyst, showedvery good catalytic activity for the synthesis of 2-aminothiophenederivatives. Thus far, little research has been reported on the Gewaldreaction under solvent-free conditions; to the best of our knowledge,this is the first time that it has been proposed as an inexpensiveand readily available catalyst for use in the target synthetic route. [ABSTRACT FROM AUTHOR]

Abstract: An ultrasound promoted easy, efficient, and environment friendly process has been devised for the synthesis of α-aminophosphonates within seconds through a one-pot three-component condensation of the aldehydes, amines, and triethylphosphite. The desired products were obtained in excellent yields and in high purity under solvent-free and catalyst-free conditions. Study with various aldehydes and amines reveals that ultrasound radiation plays a key role in the direct synthesis of α-aminophosphonates. [Copyright &y& Elsevier]

Abstract: A new green protocol has been developed for the synthesis of fluorine containing 2,4,5-trisubstituted imidazoles via one-pot, three-component condensation reaction of 4,4-difluorobenzil with aldehydes and ammonium acetate using reusable indium (III) fluoride (InF3) as Lewis acid catalyst under solvent-free conditions. This protocol provides a novel and improved method for obtaining fluorine containing 2,4,5-trisubstituted imidazoles in terms of good yields with little catalyst loading. [Copyright &y& Elsevier]

A facile one-pot synthesis of 5-(trifluoromethyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine derivatives is described via a three-component reaction of aldehydes with 5-aminotetrazole and ethyl 4,4,4-trifluoro-3-oxobutanoate or 4,4,4-trifluoro-1-phenylbutane-1,3-dione in ionic liquid. This method has the advantages of short synthetic route, operational simplicities, good yields, ecofriendliness, and recyclability of the solvent. [ABSTRACT FROM AUTHOR]

Abstract: An efficient and organo-catalyzed method has been developed for the synthesis of 5-arylidenethiazolidine-2,4-diones and 5-arylidene-2-thioxothiazolidin-4-ones via Knoevenagel condensation of arylaldehydes 1 and 2,4-thiazolidinedione 2a/2-thioxothiazolidin-4-one 2b under mild conditions. Urea-adduct 4 and azomethine 5 also afford arylidene-products 3 by reacting with 2a–b via addition–elimination reaction. This protocol has the features of use of inexpensive, ecofriendly readily available, effective catalyst system viz. urea/thiourea, avoidance of volatile solvents, excellent yield and simple work-up procedure. [Copyright &y& Elsevier]

An environmentally benign and efficient method has been developed for the synthesis of a series of benzo[4,5]imidazo[1,2-a]pyrimido[4,5-d]pyrimidin-4(1H)-one derivatives in aqueous media under catalyst-free conditions by simply combining 2-aminobenzimidazole, aldehyde, and cyanoacetamide. The advantages of this method are that it is catalyst-free, has an easy workup, provides excellent yields, and uses water as the solvent which is considered to be relatively environmentally benign. [ABSTRACT FROM AUTHOR]