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The green solvent CyreneTM has emerged as a valuable substitute for conventional polar aprotic organic solvents such as DMF, DMSO and NMP (renowned for their toxicity and environmental concerns). However, in the presence of bases, Cyrene is prone to polymerization, thus potentially incompatible with reactions where a base is needed to generate reactive nucleophiles. In this study, we developed an efficient synthetic strategy for nucleophilic aromatic substitutions of nicotinic esters in Cyrene. The success of this protocol relies on a very short reaction time (only 15 minutes) which prevents polymerization from occurring. Indeed, Cyrene not only outperformed typical solvents such as DMF and DMSO, but also, being highly soluble in water, allowed an easy purification of the desired products by simple precipitation upon the addition of ice‐water. [ABSTRACT FROM AUTHOR]

Herein, we report a new catalytic protocol for the aerobic oxidation of alcohols. The catalytic system is formed in situ, in a straightforward and user‐friendly manner, combining a widely available copper source (Cu2O) with one imidazolium salt precursor bearing perfluorinated moieties. Our protocol uses TEMPO, as additive, and the reaction takes place at the interface of a biphasic solvent system, consisting of anisole and 1‐bromoperfluorooctane. The as‐prepared carbonyl compounds remain in the organic solvent, while the catalytic system remains in the fluorous phase. In this manner, the isolation and purification of the desired products are quite facile. Our protocol uses low catalytic loadings and is more efficient with primary alcohols, affording the desired products in good to excellent yields. The fluorous phase containing the catalytic system can be efficiently recovered and reused for at least six times, without a significant decrease in its catalytic efficiency. [ABSTRACT FROM AUTHOR]

The use of volatile solvents for organic synthesis is nowadays questioned due to their negative impact on the environnement. To develop sustainable and environmentally friendly methodologies, we propose to combine two green chemistry concepts: the use of bioinspired solvents: natural deep eutectic solvents (NaDES), and mechanochemistry. Using the Suzuki‐Miyaura coupling as a model reaction, we described an efficient mechanochemical method with NaDES as a LAG (liquid‐assisted grinding) additive with short reaction times and without any ligand or additional heating. A mechanochemical extraction was also used to reduce the amounts of extraction solvents and the total time of the synthesis process. [ABSTRACT FROM AUTHOR]

The direct use of alcohols as the much greener and more sustainable alkylated reagents in substitution reactions is one of the emerging areas in green chemisty. However, owing to the poor leaving character of OH group, the direct substitution of alcohols is not an easy thing. Transition metal (TM) catalysis such as Pd‐catalyzed allylic/benzyl substitution and Ir‐catalyzed borrowing hydrogen provides efficient protocols for the direct substitution of alcohols, however, an organic solvent and servely anhydrous conditions are generally required. In recent decade, TM‐catalyzed direct substitution of alcohols in aqueous media was developed as a much greener alternative. In this review, the recent develpoments of this area are summarized. The activation mechanism of alcohols in aqueous reactions are emphatically discussed. [ABSTRACT FROM AUTHOR]

New fluorescent nucleobase analogues (FBAs) are emerging as extraordinarily useful tools for DNA labelling technologies. The highly fluorescent adenine analogue 2‐aminopurine (2AP) is still the most used within the few hundreds of newly FBAs synthesized, but its excitation in the UV region demands for high energy sources endangering living cells. New and highly fluorescent 2AP derivatives, 2‐amino‐6‐cyanopurines, were obtained using simpler but efficient synthesis method. All the new compounds exhibit advantageous photophysical properties over 2AP, showing absorption and emission bands ranging the visible region (blue‐green region), high fluorescence quantum yields and Stokes' shifts, especially in non‐protic organic solvents. Density Functional Theory calculations (DFT) of electronic and vibrational structure were performed, allowing to predict absorption and emission spectra. In addition, these 2‐amino‐6‐cyanopurines exhibit little to no toxicity in assays using yeast cells. [ABSTRACT FROM AUTHOR]

Tweezer‐type receptors that form π−π stacked supramolecular complexes are important components in functional polymeric materials and molecular machines. Herein, we study how varying specific structural components of tweezer‐receptors impacts their binding. A library of tweezer receptors, each containing two π‐electron poor receptor residues and differing by the nature of the linking unit which was either a flexible 2,2′‐(ethylenedioxy)bis(ethylamine) residue or a rigid 3,3"‐diamino‐m‐terphenyl diamine structure, were synthesised. Each tweezer formed 1 : 1 supramolecular complexes with π‐electron rich residues (1,5‐dihydroxynapthalene and pyrene) as confirmed by UV/Vis and 1H NMR spectroscopic studies. Binding constants were determined to be between 2.3×10−5 and 71 M−1 in organic solvents and were one magnitude greater in aqueous solvents for water soluble systems. The nature of the linker had variable effects on the binding constants, showing the design of tweezer type supramolecular receptors with targeted Ka values is non‐trivial and requires structural optimisation supported by binding constant determination studies. [ABSTRACT FROM AUTHOR]

Scalable protocols of straightforward synthesis of enantiomeric γ‐(acyloxy)carboxylic acids and γ‐lactones are presented. The key step is lipase‐catalyzed stereoselective acylation of γ‐hydroxycarboxylic acid sodium salt in organic solvent followed by acidification of the product, extraction and acidic relactonization of the unreacted enantiomer. The mixture of γ‐(acyloxy)carboxylic acid and γ‐lactone is separated either by extraction with solution of sodium bicarbonate or by distillation. A switch of enantioinduction of Candida antarctica lipase B along homologous nucleophiles from R configuration of γ‐hydroxyhexanoic acid salt to S configuration of the C7 and longer‐chain homologues has been disclosed. Both enantiomers of γ‐(acyloxy)pentanoic acids; γ‐(acetyloxy)octanoic and ‐nonanoic acids with S configuration; [(1S,5R)‐5‐(chloroacetyloxy)cyclopent‐2‐en‐1‐yl]acetic acid and enantiomeric γ‐lactones derived from them were prepared with e. r. >98.5/1.5. The rates of acylation of C5 to C9 homologous salts differ by three orders of magnitude but remain applicable for preparative synthesis by variation of the enzyme loading and reaction time. [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]

Preparation of organic semiconductors by solution processes is desirable to create flexible electronic devices. The use of soluble precursors, which exhibit high solubility in common organic solvents and afford the corresponding semiconducting molecules upon appropriate external stimuli such as heat and light, is a promising approach to realize this goal. Our group recently reported new soluble precursors, namely dinaphtho[1,8‐bc:1′,8′‐ef]thiepine bisimide (DNTBI) and its sulfoxide, which afforded perylene bisimide, a representative n‐type organic semiconductor, upon heating or light‐irradiation. In this work, we report the second‐generation synthetic route to DNTBI, which enabled gram‐scale and diversity‐oriented preparation of various N‐substituted DNTBIs. We also disclosed the suitable combination of leaving group (S or SO), external stimulus (heat or light), and N‐substituent to realize efficient charge transport. [ABSTRACT FROM AUTHOR]

A water‐promoted synthesis methodology for constructing 3‐sulfone propionic acids from sulfonyl hydrazides and α, β‐unsaturated propionic acids with excellent yields were reported. The green synthesis methodology was promoted by water without any catalyst, ligand and organic solvent. The D2O control experiment sufficiently proved that the 2‐hydrogen atom of 3‐sulfone propionic acid come from water. Moreover, the 3‐sulfone propionic acid derivates could be directly purified by crystallization without column chromatography. [ABSTRACT FROM AUTHOR]

Porous materials are important for various energy‐related technologies such as catalysis and separation. While porous organic cage compounds are a rather recent addition to the field of porous materials, these discrete nanocavities have since emerged as a versatile functional‐materials platform, facilitated by the solubility of the materials in common organic solvents. In contrast to other frameworks, organic cages are assembled first from modular building blocks in solution and then packed in the solid‐state in a next step. In this minireview, we highlight examples of porous organic cages with focus on how the intrinsic nanopore can be controlled and utilized, especially focusing on their synthesis and the gas sorption properties of smaller intrinsic pores of porous organic cage compounds, porous macrocycles, and other related compounds. [ABSTRACT FROM AUTHOR]

A mild, green and extra activator‐free synthesis of allylic sulfones from non‐derivatized allylic alcohols and sulfinic acids was developed and only the easily‐available Pd(PPh3)4 was used as the catalyst. This new method could be easily scaled up to gram scale, affording the target allylic sulfones in a nearly quantitative yield with water as the sole by‐product. Mechanism studies both by various NMR techniques and by theoretical calculations suggested two reaction pathways may be involved in the reaction, which are dependent on the reaction media, that is, an eight‐membered ring binding species may be formed in aqueous media between allylic alcohol, sulfinic acid and water, while a six‐membered ring binding species may be formed in common aprotic organic solvent between allylic alcohol and sulfinic acid. Both binding species may be accounted for the efficient activation of allylic alcohols via hydrogen bonding. [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]

Several dialkyl‐arylphosphine oxides were prepared, and the enantioseparation of the corresponding racemates was elaborated with host–guest complexation using TADDOL‐derivatives. The crystallization conditions were optimized and two separate crystallization methods, one in organic solvent, and the other in water, were found to yield five examples of phosphine oxides with enantiomeric excess values higher than 94 %. A gram scale resolution was performed, and both enantiomers of the methyl‐phenyl‐propyl‐phosphine oxide were separated with (R,R)‐ or (S,S)‐spiro‐TADDOL. The intermolecular interactions responsible for the enantiomeric recognition between the chiral host and guest molecules were investigated by single‐crystal X‐ray diffractional structural determinations. The similarities in the structural patterns of a few diastereomeric crystals were checked by powder X‐ray diffraction, as well. Organic solvent nanofiltration (OSN) was used as a scalable technique for the decomposition of the corresponding phosphine oxide–spiro‐TADDOL molecular complexes, and for the recovery of the phosphine oxide enantiomers and resolving agents. [ABSTRACT FROM AUTHOR]

Aryl sulfides are important motifs of bioactive molecules, which are generally synthesized by transition metal‐based coupling reactions under harsh conditions. Herein, we developed a new method that visible light along with cercosporin, produced by liquid fermentation and functioned as a cost‐effective and environmentally friendly photocatalyst, prompted the selective synthesis of aryl sulfides through C–S coupling of thiols and diazonium salts under mild conditions. Furthermore, this method can also be performed with a great conversion by the direct use of cercosporin‐containing fermentation supernatant as catalytic system without organic solvent extraction. [ABSTRACT FROM AUTHOR]

In recent years, there has been an increasing tendency to use biocatalysts in industrial chemistry, especially in the pharma and fine chemical sector. Preferably, enzymes or whole cells, applied as catalysts for a specific biotransformation, are utilized in aqueous reaction media since water is the natural medium for enzymes. In numerous examples of biocatalytic systems, however, a major problem is the insolubility of hydrophobic substrates in such aqueous reaction media. Apart from lipases, many enzymes are highly sensitive to organic solvents and are inactivated by an organic medium. Therefore, a change of solvent for biotransformations from water to organic solvents is usually challenging. In this study, we investigated the synthesis of nitriles by an organic solvent‐labile aldoxime dehydratase in pure organic solvents, exemplified for the dehydration of n‐octanaloxime to n‐octanenitrile. We present a method for applications in batch as well as flow mode based on an "immobilized aqueous phase" bearing the whole cells in a superabsorber as solid phase, thus enabling the use of a purely organic solvent as "mobile phase" and reaction medium. [ABSTRACT FROM AUTHOR]

One of the most useful chemical transformations of organoboronic acids is the Suzuki–Miyaura cross‐coupling reaction. Although it has vast application, it possesses some limitations: boronic acids can be difficult to quantify accurately due to their tendency to form oligomeric anhydrides and they must be activated under basic conditions. To address these problems, a new class of boronic acid derivatives is described. Phenoxy‐dialkoxy borates are prepared under mild conditions and show good solubility in common organic solvents. These adducts can be used in base‐free metal‐catalysed cross‐coupling reactions, including orthogonal reactions with MIDA boronates and trifluoroborates. [ABSTRACT FROM AUTHOR]

In a fluorous solvent (perfluorohexane, FC‐72), a perfluoroalkyl‐substituted 2‐hydroxy‐1‐naphthaldehyde (1) was found to show greatly enhanced fluorescence when treated with certain functional secondary amines but little fluorescence response was observed with unfunctional amines as well as functional primary and tertiary amines. The study of the reaction of 1 with 2‐methylamino ethanol (8) reveals a facile cyclocondensation of the aldehyde group of 1 with this 1,2‐amino alcohol to form a 5‐membered ring oxazolidine product which turns on the fluorescence. The reaction of 1 with the amino alcohol was found to be more favorable in the fluorous solvent than in a common organic solvent. The use of the fluorous phase‐based fluorescence measurement in this work provides a potentially more sensitive as well as selective method in amine sensing. [ABSTRACT FROM AUTHOR]

We developed an environmentally benign Ritter reaction of alcohols with nitriles using a commercially available bismuth salt as a less harmful catalyst. The detailed reaction profiles revealed that consumption of the ether by‐product as the reaction proceeded was the key for optimizing this reaction, and the yield of the target amide was improved by adding a small amount of water. This finding clearly reveals the significance of using a bismuth salt as the catalyst, as it is not deactivated in the presence of water. This catalyst system has a broad substrate scope, and even with 1 mol‐% of the catalyst, the reaction progresses smoothly. It is also possible to react stoichiometric amounts of nitriles and alcohols, thus reducing the amount of organic solvent required for the reaction. Furthermore, as the inexpensive bismuth catalyst can be easily removed using aqueous hydrochloric acid, a purification process that only required washing and drying without any organic solvents was successfully established. We developed the environmentally benign Ritter reaction using commercially available, less harmful bismuth salt as a catalyst. The reaction proceeded smoothly even using stoichiometric amount of nitrile to alcohol without any solvents. We also succeeded in establishing a purification process without using any organic solvents. [ABSTRACT FROM AUTHOR]

Organic synthesis without an organic solvent is still the exception. In this microreview, we discuss and compare different synthetic methods that proceed in the absence of conventional organic solvents. This includes solvent‐free methods in solids (mechanochemistry and solid‐state photochemistry), and in neat liquids (thermal and photocatalytic), as well as the application of unconventional solvents, such as ionic liquids and deep‐eutectic solvents. The different approaches are briefly introduced and examples illustrate their specific advantages, followed by a critical discussion of their limitations. Some methods have the intrinsic benefits of solvent‐free operation, such as avoiding solubility problems and side‐reactions with the solvent. However, every method has specific advantages and the demand of the synthetic application is crucial for selecting the best technique. [ABSTRACT FROM AUTHOR]

A simple and practical procedure for the oxidation of vinyl selenides into the corresponding selenones using Oxone in water at 60 °C has been reported. Structurally diverse phenyl vinyl selenones were oxidized under heterogeneous conditions without organic co‐solvents or additional catalysts. [ABSTRACT FROM AUTHOR]

Oxidative dearomatization of indoles with 70 % aqueous tert-butylhydroperoxide (TBHP) in the absence of any metal salts/organic solvents gave the corresponding C2/C3-quaternary indolinones under open-air reaction conditions. The nature of substituent on the indole nitrogen dictates the type of product formed in these reactions. Free (NH)-indoles gave C2-quaternary indolinone derivatives whilst (NR)-indoles yielded C3-quaternary indolinones as the major product. Moreover, the addition of an excess amount of TBHP also facilitated the one-pot transformation of (NR)-indoles to the corresponding isatin derivatives. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) can behave as green solvents in comparison with conventional organic solvents, but more often they also act as ligands, co-catalysts, and stabilizing agents both for metal active species and for intermediates of catalytic systems. In this review we have mainly summarized the recent achievements (2013 to the present) in Pd-catalyzed cross-coupling in ILs for the assembly of structurally diverse and highly functionalized organic molecules, with the focus on cascade reactions triggered by nucleopalladation, Suzuki coupling, Sonogashira coupling, allylic functionalization, and other types of coupling. The reaction conditions, regio- and stereoselectivities, and mechanisms are summarized in detail. We also highlight important and representative examples and synthetic applications of these coupling reactions. We hope that this review will result in further focused research to widen the comprehension and application of ILs in the future. [ABSTRACT FROM AUTHOR]

We report visible color changes and new intense, bathochromically shifted bands in electronic absorption spectra that reach into the near-infrared region (up to 862 nm) upon protonation of nine pentafulvene and expanded pentafulvalene derivatives. This phenomenon can only be explained by the formation of carbocations with highly delocalized charges. Solution pKa values in organic solvents were determined, making use of the method of relative basicity measurements. All seven 6-phenylpentafulvenes are weak bases, and pKa values of the protonated forms range from 0.92 to 10.29 in acetonitrile and from 1.3 to 5.9 in 1,2-dichloroethane. For 6-phenylfulvenes with varying para-substituents on the phenyl ring, pKa values correlate well with the Hammett parameters σpara. Furthermore, for most compounds, electrochemical reduction is significantly facilitated by protonation. Extensive theoretical and NMR studies strongly support the postulated protonation at carbon. [ABSTRACT FROM AUTHOR]

Bambusurils are recently developed neutral anion receptors that show a high affinity towards many inorganic anions, not only in organic solvents but also in water. However, the number of water-soluble bambusurils and also those bearing functional groups is very limited. In this paper we report the synthesis of four- and six-membered bambusurils containing eight and twelve nitro groups. All the nitro groups on the bambusuril portals could be transformed into amino functions, which provided the macrocycles with water solubility and allowed their further modification. For example, we have demonstrated the conversion of amino groups on the bambusurils into the corresponding urea-functionalized bambusuril derivatives. We also report the first example of a bambusuril bearing only two functional groups, which was prepared by the condensation of two different glycolurils. [ABSTRACT FROM AUTHOR]

A method for the catalyst-free C-H sulfenylation of imidazo[1,2-a]pyridines by using sulfonothioates as an odorless thioarylated reagent in aqueous medium was developed. This protocol was used for a variety of substituted imidazo[1,2-a]pyridines with broad functional-group tolerance and was extended to the sulfenylation of indoles and imidazothiazoles. The sulfonothioates were activated exclusively in aqueous medium rather than in an organic solvent, and the feasibility of the process for scale-up studies was demonstrated. [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]

We describe the synthesis of architectures that consist of a symmetrical rodlike oligo(phenylene-ethynylene) (OPE) backbone of incrementable length connected to a pair of classical ligands for metal coordination. OPE spacers decorated with various end groups and incorporating up to seven phenylene-acetylene repeat units were quickly obtained through a bidirectional approach. Efficient further functionalization with useful coordinating groups were achieved. The resulting homoditopic platforms are of interest in numerous fields ranging from supramolecular chemistry to materials science. [ABSTRACT FROM AUTHOR]

Palladium(II) catalysis was found to be effective for intramolecular C-H amination in water. With 2-azidobiphenyls as substrates, the reaction efficiently provided various carbazoles with N2 as the sole byproduct. The reaction showed high functional-group tolerance and could be used in the synthesis of several natural carbazole alkaloids. The catalytic process was promoted by water, and the reaction was inefficient in the organic solvents that were investigated. [ABSTRACT FROM AUTHOR]

A two-step reaction sequence for accessing meso-(dialkoxyphosphoryl)porphyrins from readily available trans-A2-type porphyrins was developed. This approach involves bromination and subsequent palladium-catalyzed phosphonylation. Optimal conditions for both steps were identified after exploration of various reaction parameters such as solvent, temperature and catalyst. A series of dialkoxyphosphoryl-substituted A2B-porphyrins Zn3( a- g) bearing electron-donating, electron-withdrawing or sterically bulky substituents at the meso-aryl groups were prepared in overall yields close to 40 %. These compounds, being air-stable and soluble in most organic solvents, are valuable synthetic intermediates because they can be readily transformed into functionalized trans-A2BC-type porphyrins through regioselective functionalization at the unsubstituted meso position of the macrocycle. Therefore, this approach offers considerable promise for application to the synthesis of trans-A2BC-type porphyrins, including water-soluble derivatives, push-pull chromophores and bis(porphyrin)s. [ABSTRACT FROM AUTHOR]

A procedure that enables access to α-(hydroxyalkyl)butenolides from 2-(trimethylsilyloxy)furan and keto esters with excellent regiocontrol is reported. Despite their synthetic significance, there is a general lack of catalytic methodology for the α-regioselective Mukaiyama-type aldol reaction of O-silylated dienolates. We demonstrate that the challenging competition between the α and γ positions of the nucleophilic dienolate can be controlled by the use of aqueous solvent. This phenomenon, which is observed for 2-(trimethylsilyloxy)furan, can be further extended to the reaction of 2-(trimethylsilyloxy)thiophene and, less efficiently, to 2-(trimethylsilyloxy)pyrrole. Moreover, initial application of water-compatible chiral zinc complexes composed of ( R, R)-diphenylethylenediamine-based ligands affords enantiomerically enriched α-addition products in good yields (up to 72 %) and with good enantioselectivity (up to 55 % ee). [ABSTRACT FROM AUTHOR]

Regioselective, tin-free sulfation of a number of unprotected glycopyranosides derived from L-fucose, L-rhamnose, D-arabinose, D-glucose, D-galactose, and D-trehalose was achieved by using phenylboronic acid for masking the hydroxy groups and a 2,2,2-trichloroethyl-protected sulfurylimidazolium salt as the sulfating reagent. The formation of phenylborate ester remarkably improved the solubility of the carbohydrates in organic solvents and indicated high reactivity and regioselectivity in the sulfation reactions. This methodology was successfully adapted to result in a one-pot procedure that did not require separation or purification of the reaction intermediates. [ABSTRACT FROM AUTHOR]

This microreview summarizes the use of deep eutectic solvents (DESs) and related melts in organic synthesis. Solvents of this type combine the great advantages of other proposed environmentally benign alternative solvents, such as low toxicity, high availability, low inflammability, high recyclability, low volatility, and low price, avoiding many disadvantages of the more modern media. The fact that many of the components of these mixtures come directly from nature assures their biodegradability and renewability. The classification and distribution of the reactions into different sections in this microreview, as well as the emphasis paid to their scope, easily allow a general reader to understand the actual state of the art and the great opportunities opened, not only for academic purposes but also for industry. [ABSTRACT FROM AUTHOR]

The organocatalytic asymmetric Michael addition of aldehydes to a nitro olefin in aqueous organic solvents catalysed by a broad range of simple primary amines and amino alcohols is reported. In particular, the use of ( S, S)-diphenylethylenediamine, which is the chiral backbone of various organocatalysts, gave addition products in good yields and with good to high enantioselectivities (45-96 % ee). Remarkably high enantioselectivities were observed for the demanding conjugate addition of α,α-disubstituted aldehydes to nitrostyrene (96-98 % ee) in aqueous organic solvent mixtures. [ABSTRACT FROM AUTHOR]

Cyclotriphosphazene and cyclotetraphosphazene appended with six and eight sapphyrin units, respectively, were prepared by treating N3P3Cl6 and N4P4Cl8 with the appropriate equivalents of 5,10,15-tri( p-tolyl)-20-(4-hydroxyphenyl)-25,27,29-trithiasapphyrin in tetrahydrofuran (THF) in the presence of Cs2CO3 at temperatures of 0 to 60 °C for 8-12 h. The two multi-expanded porphyrin assemblies were soluble in common organic solvents, and their identities were confirmed by their corresponding molecular ion peak in the MALDI-TOF mass spectra. 1D and 2D NMR spectroscopic techniques were used to deduce the molecular structures of the mult-expanded porphyrin assemblies. Absorption spectral studies showed that the band positions of the multisapphyrin assemblies were similar to that of the monomeric sapphyrin, but the extinction coefficients were three- to fourfold higher than that of the monomeric sapphyrin. The multisapphyrin assemblies are not very stable under redox conditions. [ABSTRACT FROM AUTHOR]

A novel quinoline-substituted crown ether has been synthesized as a receptor for ion pairs and its binding behavior was investigated in various solvents. The binding of ion pairs in [D6]DMSO and in mixed [D6]DMSO/CD3CN/CDCl3 solvents was studied and the results revealed positive cooperativity effects. As a novel solubilizing agent, the crown ether can extract halide salts into organic media, especially chloride salts. ESI MS provided evidence for the formation of salt-receptor complexes. A recycling experiment showed that the receptor can solubilize salts and can be recovered. This process can be performed as a cycle. This study validates the idea that a straightforward combination of a common anion receptor and a well-studied cation complexation moiety enables the formation of ion-pair receptors and solubilizers of salts in organic solvents. [ABSTRACT FROM AUTHOR]

Here we present a new formulation of the recently introduced OxymaPure additive for peptide bond formation, in which the N-hydroxylamine group is replaced by a potassium salt. The complete suppression of its acidity converts K-Oxyma into the most suitable coupling choice when peptides are assembled on highly acid-labile solid-supports. The coupling efficiency and diminished prospects for epimerization are conserved relative to OxymaPure. In addition, K-Oxyma displays excellent solubility in a variety of organic solvents and undergoes safer decomposition than classical 1-hydroxybenzotriazole additives. [ABSTRACT FROM AUTHOR]

The lipase-catalyzed regioselective acylation of methyl α- D-galacto-, -gluco- and -mannopyranosides with isopropylidene-protected ( R)- and ( S)-glyceric acid methyl esters in organic solvents is presented. Factors affecting the formation of the 6- O-mono- and 2,6- O-diacylated products are examined and preparative-scale reactions are detailed. In addition, studies on partially protected methyl α- D-galactopyranosides are presented, with the 3,4- O-isopropylidene protected compound leading exclusively to the formation of the 6- O-monoacylated product even at high substrate concentrations. Application of acidic resin in methanol allows removal of the isopropylidene protection groups without disturbing the ester bond at C-6. [ABSTRACT FROM AUTHOR]

The solution conformations of the αγ-hybrid oligopeptides Boc-[Aib-γ4( R)Val] n-OMe ( n = 1-8) in organic solvents have been probed by NMR, IR, and CD spectroscopic methods. In the solid state, this peptide series favors C12-helical conformations, which are backbone-expanded analogues of 310 helices in α-peptide sequences. NMR studies of the six- ( n = 3) and 16-residue ( n = 8) peptides reveal that only two NH protons attached the N-terminus residues Aib(1) and γ4( R)Val(2) are solvent-exposed. Sequential N iH-N i+1H NOEs characteristic of local helical conformations are also observed at the α residues. IR studies establish that chain extension leads to a large enhancement in the intensities of the hydrogen-bonded NH stretching bands (3343-3280 cm-1), which suggest elongation of intramolecularly hydrogen-bonded structures. The development of C12-helical structures upon lengthening of the αγ sequence is supported by the NMR and IR observations. The CD spectra of the (αγ) n peptides reveal a negative maximum at ca. 206 nm and a positive maximum at ca. 192 nm, spectral feature that are distinct from those of 310 helices in α-peptides. [ABSTRACT FROM AUTHOR]

The Front Cover shows a piece of ice in one glass and water in another glass; the former represents the solid phase of an unsubstituted directly‐2,2'‐linked tetracene dimer (2,2'‐TD), and the latter is the solution of the multi‐substituted 2,2'‐TD. The unsubstituted 2,2'‐TD reported by Rehan's group in 2017 could not be characterized, which may have been be due to its low solubility. On the other hand, the multi‐substituted 2,2'‐TD was highly soluble in organic solvents and could be characterized by several techniques such as NMR, UV/Vis spectroscopy, and X‐ray crystallography. More information can be found in the Full Paper by T. Honda, C. Kitamura et al. [ABSTRACT FROM AUTHOR]

“We are thus able to apply our synthetic receptors, which typically work in solution, in real‐world sensing devices …” Find out more about this author's research at https://doi.org/10.1002/ejoc.201701602. “We are thus able to apply our synthetic receptors, which typically work in solution, in real‐world sensing devices …” Find out more about this author's research at https://doi.org/10.1002/ejoc.201701602. [ABSTRACT FROM AUTHOR]