articles+ search results

INFRARED spectra, BENZENE, OPTICAL constants, ABSORPTION coefficients, and ORGANIC chemistry

Infrared spectroscopic results on benzene (C 6 H 6) ices from two recent papers, one published here, are compared to each other and to literature results from 60 years ago. Qualitative and quantitative differences are described, partly in terms of spectral resolution, and errors in one paper are identified that, once corrected, could bring the two recent publications into agreement with each other. A solution is provided for an unexplained disagreement with the literature noted by the authors of one paper. It is concluded that the only accurate, extensive set of IR absorption coefficients, band strengths, and optical constants now available for amorphous and crystalline benzene are those recently published here by the author and a colleague. Suggestions are made for future work to change this situation. • Laboratory results from two recent papers on benzene ices are compared. • Multiple tests suggest conflicting results and possible corrections to them. • The data can lead to determinations of molecular abundances in extraterrestrial ices. [ABSTRACT FROM AUTHOR]

CATALYSTS, DESULFURIZATION, CARBON emissions, ORGANIC chemistry, CARBON disulfide, and INTERMEDIATES (Chemistry)

Hydrodesulfurization is well established in the industry while costly and environmentally unfriendly due to CO 2 emissions and H 2 S production. An alternative, cost-effective desulfurization process remains unreported. Here, we demonstrate a desulfurization process for dibenzothiophene, one of the most well-known and recalcitrant sulfur-containing model compounds against catalytic desulfurization, under the regulation of methane instead of hydrogen over a combination of two catalysts, generating a new sulfur-containing product, CS 2 , as an important intermediate in organic chemistry and non-polar solvent with lower environmental impact than H 2 S. A catalytic mechanism is proposed and supported by extensive experimental and computational evidence. It is discovered that methane acts as a critical initiator and intensifies the direct desulfurization pathway, where two catalysts must work cooperatively and a surface sulfur transfer process is indispensable. This study explores an alternative desulfurization route with unique reaction pathways towards CS 2 formation, whose practical potential is also supported by the desulfurization performance over a series of real-world crude samples. [Display omitted] • Methane-regulated catalytic desulfurization of dibenzothiophene is realized. • Methane initiates a direct desulfurization pathway and ends up in final products. • Carbon disulfide is observed as an environmentally benign sulfur-containing product. • A dual catalyst system is designed and the mechanism is proposed and verified. • Real-world sample desulfurization practices confirm the technical feasibility. [ABSTRACT FROM AUTHOR]

CATALYSTS, CYCLOHEXENE, ORGANIC chemistry, CHEMICAL reactions, CERIUM oxides, and CATALYTIC oxidation

• Ultrasonic impregnation of Co, Ce or Co-Pd active phase on γ-Al 2 O 3 is presented. • Ultrasounds influences higher metal distribution and smaller crystallites and grains. • Characterization methods indicate Co as Co 3 O 4 or CoAl 2 O 4 and Ce in the form of CeO 2. • The addition of Pd to Co/γ-Al 2 O 3 do not influence the status of cobalt. • Ultrasonic irradiation increases surface area and decreases pore size and pore volume. The oxidation of cyclohexene belongs to the most important reactions in organic chemistry and leads to the production of the precursors for surfactants, polymers, agrochemicals, and drugs. So far, however, due to a complex reaction mechanism, it was hard to find the catalyst of satisfactory properties. Attractive catalysts in this reaction could be sonochemically prepared Co, Ce, and Pd containing γ-Al 2 O 3 , which is the object of the undertaken research. What is more, this combination of metals in the oxide system has not been studied. The analysis of catalytic performance indicated that all studied catalysts were active in the catalytic oxidation of cyclohexene. For metal-containing alumina (Me=Co, Ce, Pd), the conversion of cyclohexene was 61–84%. The best catalyst was Co 5 Ce 5 /γ-Al 2 O 3 s , prepared via the sonochemically-assisted procedure. It was also shown that the application of ultrasonic irradiation during the preparation of samples enhanced metal distribution over alumina support, resulted in smaller crystallites of prepared materials, and caused higher surface area with simultaneous smaller both pore size and pore volume in comparison with counterparts prepared via the standard procedure. XRD, Ra, and DR..-UV–vis spectroscopies indicated the coexistence of Co as Co 3 O 4 and CoAl 2 O 4 spinel, however, Ce was found in the form of CeO 2. The addition of Pd to Co/γ-Al 2 O 3 did not influence the status of cobalt. [Display omitted] [ABSTRACT FROM AUTHOR]

MEASUREMENT of viscosity, DIFFUSION coefficients, STABILITY constants, AQUEOUS solutions, ORGANIC chemistry, TEMPERATURE measurements, CARBONATE minerals, and GLYCERIN

[Display omitted] • Diffusivity, density and viscosity for GC in H 2 O were measured at 283.15 K–313.15 K. • The activation energy and the hydrodynamic parameters were calculated. • Data analysis suggests the formation of hydrogen bonded GC-GC dimers. • Formation constant, diffusivity and hydrodynamic radius were calculated for the dimer. Glycerol Carbonate (4-hydroxymethyl-2-oxo-1,3-dioxolane, GC) is an emerging green reactant for many organic chemistry applications. GC popularity stems from its high reactivity, which makes it attractive for many chemical transformations and for its easy synthesis from glycerol, a byproduct of biodiesel production. While extensive literature covers the synthesis and chemical reactivity of GC, its transport properties are poorly studied, especially in water. Here, we measured for the first time the diffusion coefficient of GC in water in the temperature range 283.15–313.15 K and for concentrations up to 0.1 M. By taking advantage of the Taylor Dispersion Analysis (TDA) we found D 0 = 9.53 ± 0.06 × 10 - 10 m2/s at 298.15 K and an activation energy for the diffusion process E a = 3.74 ± 0.09 kcal/mol. Density and dynamic viscosity were also measured in the same temperature interval to calculate the hydrodynamic radius of GC. Experimental data helped in assessing the structure of GC aggregates formed in aqueous solutions and provided an estimation of the equilibrium constant for the dimer formation. Our findings can be useful for studying the fate of GC in the environment and to improve its use for applications in aqueous media. [ABSTRACT FROM AUTHOR]

TITANIUM catalysts, ALLYL alcohol, HYDROGEN peroxide, EPOXIDATION, ALCOHOL oxidation, ALCOHOL drinking, and TETRAHYDROFURAN

In the Sharpless asymmetric epoxidation of chiral secondary allylic alcohols, one substrate enantiomer is predominantly converted to the anti‐epoxy alcohol. We herein report the first highly syn‐selective epoxidation of terminal allylic alcohols using a titanium salalen complex as catalyst, at room temperature, and aqueous hydrogen peroxide as oxidant. With enantiopure terminal allylic alcohols as substrates, the epoxy alcohols were obtained with up to 98 % yield and up to >99 : 1 dr (syn). Catalyst loadings as low as 1 mol % can be applied without eroding the syn‐diastereoselectivity. Modification of the allylic alcohol to an ether does not affect the diastereoselectivity either [>99 : 1 dr (syn)]. Inverting the catalyst configuration leads to the anti‐product, albeit at lower dr (ca. 20 : 1). The synthetic potential is demonstrated by a short, gram‐scale preparation of a tetrahydrofuran building block with three stereocenters, involving two titanium salalen catalyzed epoxidation steps. [ABSTRACT FROM AUTHOR]

Depressants are critical reagents for the selective separation of minerals in froth flotation. They serve a vital role in preferentially making the gangue minerals hydrophilic and prevent them from reporting to the mineral-rich froth phase. Current practice involves the use of inorganic depressants, which are toxic and non-biodegradable. Environmentally friendly, flexible and affordable flotation depressants are needed due to the depletion of easy-to-process high-grade ores as well as sustainability and environmental concerns. This paper discusses various organic depressants that have been adopted for selective depression of unwanted minerals in chalcopyrite flotation. The origin and chemistry, organic depressant-gangue minerals interaction mechanism, and the use of organic depressants in the most common chalcopyrite-flotation instances, including chalcopyrite separation from galena, molybdenite, sphalerite, pyrite, pyrrhotite, talc, serpentine and carbonaceous materials, are discussed. This review shows that organic depressants can partially or fully replace current inorganic depressants used in suppressing both sulfide and non-sulfide gangue minerals in chalcopyrite flotation. In this review, a well-detailed and well-referenced discussion is provided for the current state of organic depressants in chalcopyrite flotation, as well as a valuable discussion is provided to comparatively evaluate the depression performance of the various reported organic depressants. Finally, suggestions are made regarding future research challenges and directions. The recent advancements, developing features, and research prospects discussed in this article will provide a helpful reference for academics who want to delve deeper into the greening of chalcopyrite flotation process. [ABSTRACT FROM AUTHOR]

The discovery and development of new synthetic methods exploiting earth-abundant-element-based catalysts is an important goal in contemporary synthetic organic chemistry, which faces increasingly stringent requirements of sustainability. In this work, we disclose alumina-mediated propargylic C–H activation inducing a challenging transformation of readily available alkynes into a valuable 1,3-diene moiety under unprecedentedly mild conditions. Combining DFT-investigation and synthetic observations, we demonstrate that partial hydroxylation of alumina's surface might play an essential role in this process. [ABSTRACT FROM AUTHOR]

EYE tracking, CHEMISTRY education, ORGANIC chemistry, and RESONANCE

Drawing structural formulas is of great importance in organic chemistry. As such, they serve as an important communication and problem‐solving tool. By constructing resonance structures, it is possible, for example, to derive reactivities and structural properties of compounds. Although chemistry education research has emphasized the difficulties that learners encounter concerning the resonance concept, the drawing process of resonance structures has not been examined yet. In this regard, the use of eye‐tracking can help to shed light on the drawing process in a process‐oriented and detailed manner. Therefore, this paper presents excerpts of a study investigating the drawing process of resonance structures as an example to show the possibilities that the use of eye‐tracking offers for analyzing construction processes. [ABSTRACT FROM AUTHOR]

ORGANIC chemistry, MOIETIES (Chemistry), PROTON transfer reactions, ANTIAROMATICITY, AMIDINES, X-ray diffraction, and PYRIDINE

The switching of cyclic π‐conjugation pathways using external stimuli is an attractive research topic in the field of organic chemistry. Here, we synthesized C4h‐symmetric octaaza[8]circulenes with four peripherally arranged amidine moieties that exhibit enhanced antiaromaticity upon protonation. Titration experiments with methanesulfonic acid revealed the formation of the tetraprotonated forms of the octaaza[8]circulenes in solution. Single‐crystal X‐ray diffraction analyses and theoretical calculations indicated that the contribution of the 8π antiaromatic character of the octaaza[8]circulenes is enhanced by the delocalization of charge through the protonation of the pyridine rings. [ABSTRACT FROM AUTHOR]

ELECTRON configuration, MATERIALS science, EDITORIAL boards, ORGANIC chemistry, PHYSICAL organic chemistry, POLYMERIZATION, and SUPRAMOLECULAR chemistry

The article presents the discussion on the research of editorial board members. Topics include Sheng Dai showing heterogeneous catalysis being a key process for converting reactants into products playing a critical role in chemical and energy transformations; and Dechao Geng showing chemical vapor deposition (CVD) method compelling benefits in shaping 2D material single crystals due to high controllability, high scalability, and ultra-low cost.

SOLAR cells, PYRENE, SURFACE interactions, THIOPHENES, and SELENOPHENE

A new class of polymeric hole‐transport materials (HTMs) are explored by inserting a two‐dimensionally conjugated fluoro‐substituted pyrene into thiophene and selenophene polymeric chains. The broad conjugated plane of pyrene and "Lewis soft" selenium atoms not only enhance the π–π stacking of HTM molecules greatly but also render a strong interaction with the perovskite surface, leading to an efficient charge transport/transfer in both the HTM layer and the perovskite/HTM interface. Note that fluorine substitution adjacent to pyrene boosts the stacking of HTMs towards a more favorable face‐on orientation, further facilitating the efficient charge transport. As a result, perovskite solar cells (PSCs) employing PE10 as dopant‐free HTM afford an excellent efficiency of 22.3 % and the dramatically enhanced device longevity, qualifying it among the best PSCs based on dopant‐free HTMs. [ABSTRACT FROM AUTHOR]

ORGANIC synthesis, CATALYST synthesis, ORGANIC chemistry, LEWIS acids, HETEROGENEOUS catalysis, and GLYCOSAMINOGLYCANS

Sulfated titania (TiO2‐SO42−) is a unique and versatile catalytic material which is non‐toxic, non‐corrosive, non‐pollutant and easily separable in nature. Sulfated titania can engage in various organic reactions, as it contains both Lewis acid and Bronsted acid sites. A wide number of organic reactions in the presence of sulfated titania have been reported, most of which displays excellent conversion and selectivity for the syntheses of desired products with significant applications. This review endeavors to give an overview of the research highlights solicitous with sulfated titania. Even though it is arduous to cover all the research articles in the literature, various milestones in the route towards highly functionalized sulfated titania are explored. It is hoped that this review article will trigger the attention of researchers over sulfated titania for the advancement of new eco‐compatible approaches in organic chemistry. [ABSTRACT FROM AUTHOR]

METALS, CYCLOPROPANE, DIOLEFINS, MOIETIES (Chemistry), INDUSTRIAL applications, and ALLYLIC amination

Biologically potent and synthetically significant 1,2‐dihydronaphthalene derivatives have gained considerable attention due to their wide applications in industrial as well as in medicinal fields also. A mild and efficient metal‐free protocol via the rearrangement of cyclopropylcarbinols has been reported to construct these 1,2‐dihydronaphthalene skeletons utilizing cyclopropane ring as the scaffold. We obtained conjugated dienes and, in some cases, homoallylic chlorides as major products in good to excellent yields. They have no literature precedence till date. The fate of this rearrangement depends on the substituent patterns of the cyclopropane bearing aryl moiety. Besides the synthetic studies, to get deep insight into the electronic transitions, time dependent DFT studies have also been performed. [ABSTRACT FROM AUTHOR]

Abstract \nHIGHLIGHTS Quinoline heterocycles have been considered important structures due to their diverse applications in organic synthesis, coordination chemistry, as well as in the fields of drug design and development. Consequently, many researchers around the globe have focused on the production of these molecules as objective lead compounds and exploit their biological activities. Herein, the presented review provides an overview of anticancer agents and natural sources of quinolines and includes a summary of marketed drugs. Advanced synthetic analogs of quinoline derivatives and their anticancer activity have been provided. Quinoline natural sources for anticancer activity. Marketed drugs of quinolines Synthetic derivatives of quinolines bearing anticancer activity are revealed. Quinoline natural sources for anticancer activity.Marketed drugs of quinolinesSynthetic derivatives of quinolines bearing anticancer activity are revealed. [ABSTRACT FROM AUTHOR]

ENANTIOSELECTIVE catalysis, PHOSPHORUS, ORGANIC chemistry, DIASTEREOISOMERISM, and DIASTEREOISOMERS

The stereoselective synthesis of molecules bearing stereogenic phosphorus(V) centers represents an enduring challenge in organic chemistry. Although stereospecific nucleophilic substitution at P(V) provides a general strategy for elaborating optically active P(V) compounds, existing methods for accessing the requisite chiral building blocks rely almost entirely on diastereocontrol using chiral auxiliaries. Catalytic, enantioselective methods for the synthesis of synthetically versatile stereogenic P(V) building blocks offer an alternative approach to stereogenic-at-P(V) targets without requiring stoichiometric quantities of chiral control elements. Here, we report an enantioselective hydrogen-bonddonor-catalyzed synthesis of aryl chlorophosphonamidates and the development of these products as versatile chiral P(V) building blocks. We demonstrate that the two leaving groups on these chlorophosphonamidates can be displaced sequentially and stereospecifically to access a wide variety of stereogenic-at-P(V) compounds featuring diverse substitution patterns. [ABSTRACT FROM AUTHOR]

ORGANIC chemistry, BIOCATALYSIS, CHEMISTS, DRUG discovery, ENZYMES, and FIRST aid kits

First Aid Kits are collections of the most important medical equipment required for quick medical assistance. Similarly, enzyme kits can provide a proficient, ready‐ and easy‐to‐use collection of biocatalysts that can be applied with high reproducibility. In this article, we illustrate how kits of oxyfunctionalisation enzymes could operate as synthetic 'First Aid' for chemists working on complex natural product total synthesis in an early‐ or late‐stage fashion, as well as in lead diversification in drug discovery processes. We reason that enzyme kits could catalyse the integration of biocatalysis into (synthetic) organic chemistry and describe how we envision their future application. [ABSTRACT FROM AUTHOR]

ORGANIC chemistry, BIOCATALYSIS, CHEMISTS, ENZYMES, and ORGANIC synthesis

Biocatalysis, early-stage functionalisation, enzyme kits, late-stage functionalisation, lead diversification Cover Feature: Enzyme Kits to Facilitate the Integration of Biocatalysis into Organic Chemistry - First Aid for Synthetic Chemists (ChemCatChem 11/2022) Keywords: biocatalysis; early-stage functionalisation; enzyme kits; late-stage functionalisation; lead diversification EN biocatalysis early-stage functionalisation enzyme kits late-stage functionalisation lead diversification 1 1 1 06/10/22 20220608 NES 220608 B The Cover Feature b illustrates how enzyme kits function as proficient and readily available "First Aid" for synthetic chemists, to simplify syntheses of complex molecules complementary to conventional chemical methods. [Extracted from the article]

ORGANIC chemistry, FLUORIDES, CHEMICAL biology, OXIDATION states, CHEMICAL potential, and FLUORINATION

(Hetero)arylsulfur compounds where the S atom is in the oxidation state VI represent a large percentage of the molecular functionalities present in organic chemistry. More specifically, (hetero)aryl‐SVI fluorides have recently received enormous attention because of their potential as chemical biology probes, as a result of their reactivity in a simple, modular, and efficient manner. Whereas the synthesis and application of the level 1 fluorination at SVI atoms (sulfonyl and sulfonimidoyl fluorides) have been widely studied and reviewed, the synthetic strategies towards higher levels of fluorination (levels 2 to 5) are somewhat more limited. This Minireview evaluates and summarizes the progress in the synthesis of highly fluorinated aryl‐SVI compounds at all levels, discussing synthetic strategies, reactivity, the advantages and disadvantages of the synthetic procedures, the proposed mechanisms, and the potential upcoming opportunities. [ABSTRACT FROM AUTHOR]

ETHER derivatives, BENIGN prostatic hyperplasia, ETHERS, ORGANIC chemistry, and AMIDES

Ethers are of central importance in the fields of biomass, energy, and organic chemistry. Herein, a novel cobalt‐catalyzed carbonylative coupling of ethers with amines to construct α‐carbonylated ethers has been achieved. Remarkably, Alfuzosin, a medicine for treatment of benign prostatic hyperplasia (BPH), can be synthesized by this process straightforwardly. Notably, this protocol presents the first example on the direct carbonylative reaction of ethers. [ABSTRACT FROM AUTHOR]

AUTOCATALYSIS, KINETIC isotope effects, ALDEHYDES, and ZWITTERIONS

Under aprotic conditions, the stoichiometric reaction of N‐heterocyclic carbenes (NHCs) such as imidazolidin‐2‐ylidenes with aldehydes affords Breslow Intermediates (BIs), involving a formal 1,2‐C‐to‐O proton shift. We herein report kinetic studies (NMR), complemented by DFT calculations, on the mechanism of this kinetically disfavored H‐translocation. Variable time normalization analysis (VTNA) revealed that the kinetic orders of the reactants vary for different NHC‐to‐aldehyde ratios, indicating different and ratio‐dependent mechanistic regimes. We propose that for high NHC‐to‐aldehyde ratios, the H‐shift takes place in the primary, zwitterionic NHC‐aldehyde adduct. With excess aldehyde, the zwitterion is in equilibrium with a hemiacetal, in which the H‐shift occurs. In both regimes, the critical H‐shift is auto‐catalyzed by the BI. Kinetic isotope effects observed for R‐CDO are in line with our proposal. Furthermore, we detected an H‐bonded complex of the BI with excess NHC (NMR). [ABSTRACT FROM AUTHOR]

ALDEHYDES

Keywords: Autocatalysis; Breslow Intermediate; Carbenes; NMR; Reaction Mechanisms EN Autocatalysis Breslow Intermediate Carbenes NMR Reaction Mechanisms 1 1 1 06/01/22 20220607 NES 220607 B Breslow intermediates b (BIs) are pivotal species in Umpolung catalysis effected by N-heterocyclic carbenes (NHCs). Inside Back Cover: Formation of Breslow Intermediates from N-Heterocyclic Carbenes and Aldehydes Involves Autocatalysis by the Breslow Intermediate, and a Hemiacetal (Angew. Autocatalysis, Breslow Intermediate, Carbenes, NMR, Reaction Mechanisms. [Extracted from the article]

MINERALS, COPPER smelting, ALKYNES, ORGANIC chemistry, COPPER compounds, and COPPER

Copper is one of the most abundant metals on the Earth. Elemental copper, as well as its alloys and compounds are widely used as catalysts in organic chemistry. By utilizing naturally occurring ores, the non‐eco‐friendly copper smelting process can be bypassed, leading to green and environmentally friendly procedures in comparison to the use of synthetic copper compounds. In this study we wish to present a more economical method for the production of symmetric diynes starting from various terminal acetylenes in a Glaser–Hay reaction. Out of the seven tested naturally occurring copper‐containing minerals, chalcocite (Cu2S) and bornite (Cu5FeS4) were the best applicable ones. These minerals were able to produce diynes in yields comparable to those obtained with their synthetic analogues, furthermore they proved to be partly reusable. [ABSTRACT FROM AUTHOR]

RESOLUTION (Chemistry), PEPTIDES, HYDROLYSIS, AMINO acid analysis, ORGANIC chemistry, PRIONS, AMINO acids, and ENANTIOMERS

There are several reports of d-amino acids being the causative molecules of serious diseases, resulting in the formation of, for example, prion protein and amyloid β. d-Amino acids in peptides and proteins are typically identified by sequencing each residue by Edman degradation or by hydrolysis with hydrochloric acid for amino acid analysis. However, these approaches can result in racemization of the l-form to the d-form by hydrolysis and long pre-treatment for hydrolysis. To address these problems, we aimed to identify the dl-forms of amino acids in peptides without hydrolysis. Here, we showed that the dl-forms in peptides which are difficult to separate on a chiral column can be precisely separated by labeling with 1-fluoro-2,4-dinitrophenyl-5-d-leucine-N,N-dimethylethylenediamine-amide (d-FDLDA). Additionally, the peptides could be quantitatively analyzed using the same labeling method as for amino acids. Furthermore, the detection sensitivity of a sample labeled with d-FDLDA was higher than that of the conventional reagents Nα-(5-fluoro-2,4-dinitrophenyl)-l-alaninamide (l-FDAA) and Nα-(5-fluoro-2,4-dinitrophenyl)-l-leucinamide (l-FDLA) used in Marfey's method. The proposed method for identifying dl-forms of amino acids in peptides is a powerful tool for use in organic chemistry, biochemistry, and medical science. [ABSTRACT FROM AUTHOR]

HETEROGENEOUS catalysts, PHARMACEUTICAL chemistry, ORGANIC chemistry, CHEMISTS, ANTIDEPRESSANTS, and ANTIMALARIALS

Quinazoline‐2,4(1H,3H)‐dione is a significant class of N‐fused heterocyclic with a wide range of biological functions, including anti‐HIV, anticancer, antifungal, antibacterial, antimutagenic, anticoccidial, anticonvulsant, anti‐inflammatory, antidepressant, antimalarial, antioxidant, antileukemic, and antileishmanial activities, and other activities, and has attracted great attention in organic and medicinal chemistry. As a result, all chemists and pharmaceutical chemists must be aware of many methods to make quinazoline‐2,4(1H,3H)‐dione. This review paper focuses on various methods for producing quinazoline‐2,4(1H,3H)‐diones, such as green methods and homogeneous or heterogeneous catalysts from various precursors under varied conditions. [ABSTRACT FROM AUTHOR]

LEWIS acidity, CORANNULENE, POLYCYCLIC aromatic hydrocarbons, HELICENES, and ACENAPHTHENE

We have discovered a dual (i. e., soft and hard) Lewis acidity of alumina that enables rapid one‐pot π‐extension through the activation of terminal alkynes followed by C−F activation. The tandem reaction introduces an acenaphthene fragment – an essential moiety of geodesic polyarenes. This reaction provides quick access to elusive non‐alternant polyarenes such as π‐extended buckybowls and helicenes through three‐point annulation of the 1‐(2‐ethynyl‐6‐fluorophenyl)naphthalene moiety. The versatility of the developed method was demonstrated by the synthesis of unprecedented structural fragments of elusive geodesic graphene nanoribbons. [ABSTRACT FROM AUTHOR]

LEWIS acidity, CORANNULENE, and HELICENES

Keywords: alkyne activation; alumina; buckybowls; C-F activation; geodesic nanoribbons EN alkyne activation alumina buckybowls C-F activation geodesic nanoribbons 1 1 1 06/06/22 20220601 NES 220601 B Tandem bond activation b : The dual Lewis acidity of alumina has been discovered and employed to activate C-F and triple C C bonds in a tandem manner to provide rapid access to elusive nonplanar PAHs such as -extended helicenes, buckybowls and fragments of geodesic nanoribbons. Alkyne activation, alumina, buckybowls, C-F activation, geodesic nanoribbons. [Extracted from the article]

FATTY acids, ORGANIC chemistry, OLEIC acid, DIFFRACTION patterns, INDUSTRIAL capacity, INORGANIC compounds, and X-ray diffraction

The preparation of a novel crystalline fatty lambda-zirconium phosphate oleate, λ- ZrPO 4 (OH) 0.18 (C 18 H 33 O 2) 0 · 82 (CH 3) 2 SO, is reported in this research work. The material is characterized and formulated on the basis of its elemental, TGA, FT-IR and X-ray analyses. The X-ray diffraction pattern reveals that the interlayer distance of our new fatty material is heavily increased (2.96 nm) in comparison with that of the pristine λ-ZrP (1.02 nm). Therefore, this material could have potential applications in the field of intercalation chemistry of large organic and inorganic guests. • Chloride ligand of pure λ-ZrP can be easily exchanged with fatty acids. • Oleic acid leading to the formation of novel λ-type fatty solid material. • λ-ZrP materials could be functionalized with other aliphatic and aromatic fatty acids. • λ-ZrP and these fatty solid materials could have potential industrial applications. [ABSTRACT FROM AUTHOR]

ONLINE education, DISTILLATION, LEARNING strategies, PEERS, and ORGANIC chemistry

Model distillation is an effective way to let a less-parameterized student model learn the knowledge of a large teacher model. It requires a well-trained and high-performance model in advance, which limits the application of the deep model in some multimedia devices. However, the powerful teacher is not always available. Given this, some researchers propose a strategy of learning from each student model to replace the traditional teacher–student learning paradigm. Although this way has achieved good results recently, the simple mutual learning between student networks is easy to reach saturation earlier. In this work, we propose a smarter mutual learning method called Smarter Peer Learning (SPL) for online knowledge distillation, which puts forward a weight evaluation mechanism to build a virtual teacher and a novel online distillation framework. The ensemble teacher is constructed by combining the output of student networks through the calculated weight so that students will learn more from the better performance peers in the next stage of the learning. The experiments show that our SPL can train more efficient students than some existing advanced methods by applying various backbone networks to CIFAR-10, CIFAR-100, and Tiny-ImageNet datasets. [ABSTRACT FROM AUTHOR]

PRECIOUS metals, PERICYCLIC reactions, ORGANIC chemistry, DERACEMIZATION, ORGANOCATALYSIS, ASYMMETRIC synthesis, and CRUST of the earth

"Cheap but efficient". Magnesium-catalyzed enantioselective transformations can be efficiently used for the synthesis of diverse organic molecules of a complex structure. Therefore, catalysis by Earth-abundant main group metals might be considered the third way in the development of asymmetric catalysis, combining the advantages of catalysis with noble metals and organocatalysis. [Display omitted] Magnesium (Mg) constitutes one of the most abundant metal elements in the Earth's crust. The spectacular career of magnesium in organic chemistry has been initiated at the beginning of XX century and has still been lasting today. The discovery of organomagnesium compounds by Philippe A. Barbier and Victor Grignard is commonly recognized as one of the milestones in development of (organic) chemistry. The subsequent applications of Grignard reagents as relatively easy generated synthons in enantioselective reactions have opened new possibilities for acquiring enantiomerically enriched compounds. On the other hand, asymmetric reactions in which magnesium plays a role of catalyst can be considered still limited, especially when their number is compared to the number of contributions aimed at transition metal-catalyzed or organocatalyzed stereoselective transformations. However, taking into account the current trends of replacing expensive metals with their cheaper counterparts and making catalysis more environmentally (and user) friendly, the development of new and modification of known methods, which employ Earth-abundant metals, is very advisable. In this study we intend to emphasize the role of magnesium in organic chemistry, mainly in catalytic asymmetric synthesis. Among the already reported catalytic procedures, we have discussed the most recent examples, however, we also mentioned some, the groundbreaking previous ones. An exception for the pericyclic reactions has been made, as these reactions constitute the first examples of the use of magnesium catalysis in asymmetric synthesis. An attention has been drawn to some structural aspects, associated with either experimentally-determined geometry of the catalytic species or the calculated transition state(s) for a given asymmetric transformation. [ABSTRACT FROM AUTHOR]

ORGANOSELENIUM compounds, POLYMERIZATION, and SELENIUM

The one-pot multicomponent synthetic strategy of organoselenium compounds represents an alternative and robust protocol to the conventional multistep methods. During the last decade, a potential advance has been made in this domain. This review discusses the latest advances in the polymerization, metal, and metal-free one-pot multicomponent synthesis of organoselenium compounds. [ABSTRACT FROM AUTHOR]

PARACYCLOPHANES, IONS, FLUOROPHORES, FLUORESCENCE, SKELETON, and MACROCYCLIC compounds

Transformation of [15]paracyclophanes ([15]PCP) into fluorophores has been achieved by embedding tetraphenylethene (TPE) units into their skeletons at the meso-positions. The obtained two hosts demonstrated distinct aggregation-induced emission (AIE) properties and their fluorescence could be selectively quenched by Ni2+ ions. [ABSTRACT FROM AUTHOR]

COMPUTATIONAL chemistry, ORGANIC chemistry, HOMOGENEOUS catalysis, CATALAN language, and CHEMISTRY teachers

COMPUTATIONAL chemistry, ORGANIC chemistry, HOMOGENEOUS catalysis, CATALAN language, and CHEMISTRY teachers

SULFIDES, IRRADIATION, ORGANIC chemistry, WAVELENGTHS, PHARMACEUTICAL chemistry, SULFOXIDES, OXIDATION, and DIMETHYL sulfoxide

The sulfoxide moiety is recognized as one of the most important groups in organic and medicinal chemistry. Many efforts worldwide focus on developing novel and sustainable protocols, accessing sulfoxide-containing molecules. Photochemistry plays a unique role in sulfoxide synthesis, since this new emerging field, employing light as the energy source, is essential in developing novel and eco-friendly protocols. Herein, we report a novel, sustainable, light-driven protocol, where the impact of wavelength irradiation on sulfide aerobic photooxidation was examined. In this work, two different low-catalyst loading (0.05–0.5 mol%) protocols, utilizing anthraquinone as the photocatalyst (under CFL lamps or 427 nm irradiation) were developed and a catalyst-free protocol (under 370 nm irradiation) was also assessed. In addition, a broad scope of substrates was tested and extensive mechanistic studies were performed, in order to distinguish the mechanistic pathways that are followed in the different cases of aryl or alkyl sulfide oxidation under different wavelength irradiation. We also implemented our protocols towards the oxidation of several intermediates en route to Sulforaphane. [ABSTRACT FROM AUTHOR]

ALKENES, NUCLEOPHILIC reactions, ORGANIC chemistry, CHEMICAL reactions, and DOSAGE forms of drugs

Aza‐Michael addition is known to be one of the most exploited reactions in organic chemistry. Taking into account the fact that each seventh reaction in pharmaceutical industry involves the formation of at least one C−N bond, it is not surprising that this reaction is especially valuable for the synthesis of bioactive compounds and drugs. Traditionally, only push‐pull alkenes are regarded as starting material for this reaction. The participation of pull‐pull alkenes as Michael acceptors is much less studied. The presence of two vicinal electron‐withdrawing groups makes them highly reactive in nucleophilic reactions especially with nitrogen‐centered nucleophiles. This feature allows them to be excellent building blocks in the synthesis of bioactive molecules and polyfunctional materials. The review considers the most important and sometimes unexpected results obtained over the last two decades on the conjugate addition of nitrogen nucleophiles to pull‐pull alkenes bearing various acceptor moieties (alkoxycarbonyl‐, carbonyl‐, formyl‐, cyano‐, trifluoromethyl‐ or nitro group) in various combinations. [ABSTRACT FROM AUTHOR]

TERTIARY amines, IMINES, BIOACTIVE compounds, ORGANIC chemistry, AMINES, ENOLS, and NUCLEOPHILES

Chiral α-tertiary amines, a motif present in α,α-disubstituted α-amino acids, in a wide range of natural products, and many drugs and drug candidates, are important targets in organic chemistry. Among the possible strategies, 1,2-addition to chiral N -sulfinyl-ketimines is one of the best routes to form chiral α-tertiary amines with a high level of stereoselectivity. In this review, we focus first on the addition of organometallic reagents or other nucleophiles as enols or ylides to chiral N -sulfinylketimines. Then secondly we cover a selection of applications of these additions in the synthesis of valuable biologically active compounds. 1 Introduction 2 1,2-Addition Reaction Methodologies 2.1 Organolithium Reagent Additions 2.2 Grignard Additions 2.3 Organozinc Reagent Additions 2.4 Organoindium Reagent Additions 2.5 Organoboron Reagent Additions 2.6 Strecker Reactions 2.7 Palladium-Catalyzed Reactions 2.8 Enols, Enolates, and Other Deprotonated Reagent Additions 2.9 Ylide Additions 2.10 Heteroatom Nucleophiles 2.11 Miscellaneous Reactions 3 Applications to the Synthesis of Biologically Active Molecules 4 Conclusions [ABSTRACT FROM AUTHOR]

ORGANIC chemistry, RADICAL anions, ACENES, MATERIALS science, and X-ray diffraction

Boron‐embedded heteroacenes (boraacenes) have attracted enormous interest in organic chemistry and materials science. However, extending the skeleton of boraacenes to higher acenes (N≥6) is synthetically challenging because of their limited stability under ambient conditions. Herein, we report the synthesis of boron‐embedded heptacene (DBH) and nonacene (DBN) as the hitherto longest boraacenes. The former is highly stable (even after 240 h in tetrahydrofuran), while the latter is air‐sensitive with the half‐life (t1/2) of 11.8 min. The structures of both compounds are verified by single‐crystal X‐ray diffraction, revealing a linear backbone with an antiaromatic C4B2 core. Photophysical characterizations associated with theoretical calculations indicate that both compounds exhibit highly efficient anti‐Kasha emissions. Remarkably, the air‐stable DBH manifests an ultrahigh photoluminescence quantum yield (PLQY) of 98±2 % and can be chemically reduced to its radical anion and dianion states, implying the value of boron‐doped higher acenes as novel functional materials. [ABSTRACT FROM AUTHOR]

CHELATION, AMINATION, CATALYSTS, ORGANIC chemistry, PHARMACEUTICAL chemistry, and OXIDATION states

Comprehensive Summary: Nitrogen‐containing compounds are ubiquitously found in the fields of organic chemistry, pharmaceuticals, agrochemicals, medicinal chemistry and functional materials. The C—H bond amination reaction is one of the most straightforward protocols in the C—N bond formation, showing "step" and "atomic" economy. As a catalyst for C—H amination reaction, copper exhibits its unique catalytic properties due to easily accessible oxidation states. The research progress of copper‐catalyzed C—H amination in recent years is summarized. At the same time, reaction mechanisms are also briefly described in representative aminations to provide insights for the development prospects of highly practical and more environmentally benign processes. [ABSTRACT FROM AUTHOR]

NATURAL products, NATURAL history, MEDICAL informatics, EXECUTIVE advisory bodies, ORGANIC synthesis, and ORGANIC chemistry

RAPID eye movement sleep, SOLAR cells, CYCLOHEXANE, PREFRONTAL cortex, and ORGANIC chemistry

The article focuses on several research concerning rapid eye movement (REM) sleep, solar cells and cyclohexane. Topics discussed include emotional memories consolidated during rapid eye movement (REM) sleep in prefrontal cortex, solar spectrum allowed by tandem solar cell to be used and role of analysis of disubstituted cyclohexanes in development of organic chemistry.

LIGNINS, MOLECULAR motor proteins, LIGNOCELLULOSE, TARGETED drug delivery, DRUG delivery systems, SOFT robotics, MOLECULAR switches, and LIGNIN structure

Lignin is the largest natural source of functionalized aromatics on the planet, therefore exploiting its inherent structural features for the synthesis of aromatic products is a timely and ambitious goal. While the recently developed lignin depolymerization strategies gave rise to well-defined aromatic platform chemicals, the diversification of these structures, especially toward high-end applications is still poorly addressed. Molecular motors and switches have found widespread application in many important areas such as targeted drug delivery systems, responsive coatings for self-healing surfaces, paints and resins or muscles for soft robotics. They typically comprise a functionalized aromatic backbone, yet their synthesis from lignin has not been considered before. In this contribution, we showcase the synthesis of a novel light-driven unidirectional molecular motor from the specific aromatic platform chemical 4-(3-hydroxypropyl)-2,6-dimethoxyphenol (dihydrosynapyl alcohol) that can be directly obtained from lignocellulose via a reductive catalytic fractionation strategy. The synthetic path takes into account the principles of green chemistry and aims to maintain the intrinsic functionality of the lignin-derived platform molecule. [ABSTRACT FROM AUTHOR]

LIFE sciences, ORGANIC synthesis, BIOLOGICAL networks, INDUSTRIAL chemistry, ASSOCIATION (Chemistry), and ORGANIC chemistry

We should also remind ourselves that while synthetic organic chemistry has reached a high level of sophistication - often no longer being the bottleneck in drug discovery (c.f. preclinical biological activity translation into the clinical setting) - our synthetic chemistry capabilities are still far from being perfect. The Life Science sector is currently undergoing a revolutionary transformation - powered by the convergence of biology, technology and data-driven insights. Photoredox chemistry can also enable late-stage functionalization of various chemical modalities such as peptides as highlighted by Ruf et al.Riley and co-workers have combined photoredox catalysis with flow chemistry conditions and applied this protocol to a key carbon-nitrogen bond forming reaction in the synthesis of Entrectinib (Rozlytrek®). Synthetic chemistry will be a strong enabler of Life Science innovation and expand its reach significantly (exploring abiotic RNA/DNA, amino acids/peptides, protein drug conjugates, PROTACs in addition to classical small molecules). [Extracted from the article]

ORGANIC synthesis, LIFE sciences, CONVERGENT evolution, ORGANIC chemistry, and INDUSTRIAL chemistry

In this editorial, the future role of industrial organic chemistry in life science is discussed. B The Front Cover b illustrates the convergence of innovation in biology and digital technology. Organic chemistry is both a fundamental enabler of this transformation but also benefits from scientific breakthroughs in other scientific domains. [Extracted from the article]

CHEMICAL warfare agents, LIQUID chromatography-mass spectrometry, NERVE gases, and ORGANIC chemistry

Recently, the cases of Sergei and Yulia Skripal and of Alexei Navalny have attracted considerable public interest in acetylcholine esterase inhibitors in general, and Novichok agents in particular. The name "Novichok" is given to chemical warfare agents supposedly developed in the former Soviet Union between the 1970s and the 1990s, as a reaction to the British/American invention of VX agent. These three newcomer agents were synthesized much like VX, tabun, soman, and sarin, as unitary agents, meaning that the chemical structure is altered during production so that maximum potency occurs rapidly at the outset. In response, development of binary newcomer agents escalated at GosNIIOKhT, and in 1989 the first known binary newcomer agent, Novichok-5 was synthesized off the base structure of A-232 i " (for detailed references, see Chai et al. [2]). [Extracted from the article]

ORGANIC chemistry, LIQUID chromatography-mass spectrometry, ORGANIC compounds, DINOSAURS, RAMAN spectroscopy, SMALL molecules, and SECONDARY ion mass spectrometry

Simple Summary: Fossils of dinosaurs other than birds are at least 66 million years old. Nevertheless, many organic compounds have survived fossilization and can still be found in the fossils. This article describes the discovery of organic molecules in dinosaur fossils. It provides a review of the analytical methods used for their detection and characterization, and presents the wide range of chemical organic compounds, including small molecules and polymers, that have been found in dinosaurs to date. The difficulties in unambiguously confirming the presence of some of the organic molecules in these fossils are also discussed. This review provides an overview of organic compounds detected in non-avian dinosaur fossils to date. This was enabled by the development of sensitive analytical techniques. Non-destructive methods and procedures restricted to the sample surface, e.g., light and electron microscopy, infrared (IR) and Raman spectroscopy, as well as more invasive approaches including liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), time-of-flight secondary ion mass spectrometry, and immunological methods were employed. Organic compounds detected in samples of dinosaur fossils include pigments (heme, biliverdin, protoporphyrin IX, melanin), and proteins, such as collagens and keratins. The origin and nature of the observed protein signals is, however, in some cases, controversially discussed. Molecular taphonomy approaches can support the development of suitable analytical methods to confirm reported findings and to identify further organic compounds in dinosaur and other fossils in the future. The chemical properties of the various organic compounds detected in dinosaurs, and the techniques utilized for the identification and analysis of each of the compounds will be discussed. [ABSTRACT FROM AUTHOR]

ETHYL acetate, CERVICAL cancer, GRISEOFULVIN, CELL lines, XANTHONE, and CANCER cells

Chromatographic separation of the ethyl acetate extract of the root bark of Securidaca longipedunculata led to the isolation of one new xanthone derivative (1) along with nine known compounds (2-10). The structure of the isolated compounds were identified by NMR, mass spectrometric analyses, and comparison with the reported literature data. The isolates were evaluated for their cytotoxic activity with compounds 5 (IC50 = 0.38 µM) and 6 (IC50 = 52 µM) showed significant inhibitory activities against the human cervical cancer KB-3-1 cell line. Compound 5 displayed superior activity, which is even better than one of the reference drugs (griseofulvin, IC50 = 17 µM), whereas the rest showed little or none inhibitory activities. [ABSTRACT FROM AUTHOR]

HYDROGENATION, ALKENES, DIOLEFINS, ORGANIC chemistry, SILYL enol ethers, LIGANDS, and CATALYSTS

Comprehensive Summary: Olefins are very easily accessible compounds which are both popular substrates in synthetic chemistry and good ligands in the organometallic complexes. This dual character makes olefins a rich source of chiral ligands and catalysts for asymmetric catalysis. Herein, we will briefly summarize our studies on the development of chiral diene ligands for transition‐metal catalyzed asymmetric reactions and chiral FLP catalysts for asymmetric metal‐free hydrogenations and hydrosilylations. Several acyclic chiral diene ligands as well as P/olefin and S/olefin hybrid ligands were developed for Rh or Pd‐catalyzed asymmetric reactions. With these ligands in hand, we further put forward a novel strategy for acquiring chiral FLP catalysts via the in situ hydroboration of chiral dienes with Piers' borane. These catalysts proved to be highly effective for asymmetric metal‐free hydrogenations and hydrosilylations of imines, silyl enol ethers, ketones, and aromatic N‐heterocycles. What is the most favorite and original chemistry developed in your research group? The development of acyclic dienes both as chiral ligands and as precursors of chiral FLP catalysts. How do you get into this specific field? Could you please share some experiences with our readers? When I started my independent research in 2008, chiral olefins belong to one novel ligand type. We got into the field with the thought of the simpler the better. This experience further led us to step into FLP catalysis. What is the most important personality for scientific research? Courage and persistence of doing something unique. What are your hobbies? Walking and playing cards. How do you keep balance between research and family? Life is not only research, but also family. You believe it, the balance is there. What is your favorite journal(s)? My favorite journal is Organic Letters, in which authors can publish their work rapidly and readers can browse the progress of organic chemistry comprehensively. [ABSTRACT FROM AUTHOR]

DIPHENYL, ENANTIOMERIC purity, DERACEMIZATION, ORGANIC chemistry, DIAMIDES, and NUCLEAR magnetic resonance spectroscopy

Chiral compounds with a 1,2‐diamine structure motif and their derivatives are of great interest in organic chemistry and are broadly used in asymmetric transformations, as chiral auxiliaries, (co)ligands, and ligand core structure. Here, we present a straightforward, diastereoselective synthesis for a diamide‐bridged biaryl ligand. The ring closing reaction of the racemic atropos biphenyl 6,6′‐dimethoxy‐[1,1′‐biphenyl]‐2,2′‐dicarboxylic acid with (R,R)‐diaminocyclohexane yields the diasteromerically and enantiomerically pure cyclic (Sax,R,R)‐BIPOL, which can be used as a versatile chiral ligand. By NMR spectroscopy, we observed the formation of intermolecular aggregates of the diamide‐bridged BIPOL with anhydrous DMSO‐d6. DFT calculations at the B3LYP/6‐31G* level of theory corroborate the high interconversion barrier for the biaryl axis of ΔGǂ = 148.7 kJ mol−1 and the favoured formation of (Sax,R,R)‐BIPOL as single stereoisomer. [ABSTRACT FROM AUTHOR]

ARGININE, DENSITY functional theory, FLUORESCENCE spectroscopy, ELECTROMAGNETIC spectrum, CARBOXYLATES, and SUPRAMOLECULAR chemistry

In this article, we present fluorescent guanidiniocarbonyl-indoles as versatile oxo-anion binders. Herein, the guanidiniocarbonyl-indole (GCI) and methoxy-guanidiniocarbonyl-indole (MGCI) were investigated as ethylamides and compared with the well-known guanidiniocarbonyl-pyrrole (GCP) concerning their photophysical properties as well as their binding behavior towards oxo-anions. Hence, a variety of anionic species, such as carboxylates, phosphonates and sulfonates, have been studied regarding their binding properties with GCP, GCI and MGCI using UV-Vis titrations, in combination with the determination of the complex stoichiometry using the Job method. The emission properties were studied in relation to the pH value using fluorescence spectroscopy as well as the determination of the photoluminescence quantum yields (PLQY). Density functional theory (DFT) calculations were undertaken to obtain a better understanding of the ground-lying electronic properties of the investigated oxo-anion binders. Additionally, X-ray diffraction of GCP and GCI was conducted. We found that GCI and MGCI efficiently bind carboxylates, phosphonates and sulfonates in buffered aqueous solution and in a similar range as GCP (Kass ≈ 1000–18,000 M−1, in bis-tris buffer, pH = 6); thus, they could be regarded as promising emissive oxo-anion binders. They also exhibit a visible fluorescence with a sufficient PLQY. Additionally, the excitation and emission wavelength of MGCI was successfully shifted closer to the visible region of the electromagnetic spectrum by introducing a methoxy-group into the core structure, which makes them interesting for biological applications. [ABSTRACT FROM AUTHOR]

QUINONE derivatives, MELTING points, INDOLE, THIN layer chromatography, and ORGANIC synthesis

12-Ethyl-6-methyliden-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole-3-one (4) Methyllithium (10 mL, 3.0 M MeLi solution in THF) was added to a solution of compound B 3 b (1.5 g, 5.2 mmol) in 30 mL of anhydrous THF under a nitrogen atmosphere at 0 SP ° sp C and the mixture was stirred at 0 SP ° sp C for 1 h. The organic layer was dried over magnesium sulfate, filtered, and the solvent was evaporated to give an oil, which was purified by column chromatography (silica gel, ethyl acetate:acetone:triethylamine, 4:1:1). Finally, compound B 4 b was reduced with tris(triphenylphosphine)rhodium(I) carbonyl hydride in THF to give (±)-noruleine B 5 b in four steps, with an over-all yield of 41% and also obtained as yellow oil.[21],[22],[28] All of the component compounds in the preparative sequence were rigorously characterized (see Experimental section). The uleine alkaloids (Figure 1) have remarkable biological activities and have attracted much interest from synthetic organic chemists. [Extracted from the article]

PHOTOINDUCED electron transfer, CONJUGATE addition reactions, RADIATION chemistry, ABSTRACTION reactions, and ORGANIC chemistry

Photochemistry practitioners usually associate the name of Angelo Albini to the seminal works on decatungstate-photocatalyzed radical conjugate addition reactions ( I Chem. Eur. J. i B 2006 b , I 12 i , 4153), to the invention of triplet aryl cations-based arylation processes ( I Org. This issue of I Photochemical and Photobiological Sciences i is dedicated to Prof. Angelo Albini on the occasion of his 75th birthday. [Extracted from the article]

CYCLOPROPANATION, ORGANIC chemistry, TRANSITION metal catalysts, DRUG discovery, PHARMACEUTICAL chemistry, DIAZO compounds, and CARBENE synthesis

Carbenes are important and highly reactive intermediates for the synthesis of various complex molecules. They are now an indispensable chemical species in organic chemistry and are used frequently to synthesize complex compounds in drug discovery chemistry. In general, carbenes are synthesized by a combination of transition metal catalysts and diazo compounds or by the decomposition reactions of diazo compounds. This paper reports the development of the visible light for the photochemical generation of carbenes from a novel C,Se-selenonium ylide. Overall, this photochemical carbene generation method using C,Se-selenonium ylide does not require a catalyst, is simple to perform, and enables highly efficient cyclopropanation reactions with alkenes. [ABSTRACT FROM AUTHOR]

ORGANIC chemistry and DNA ligases

Introduction to the Special Issue Dedicated to Jean Cadet† Jean Cadet received his PhD in chemistry from University of Grenoble in 1973 and continued the quest from initial research on the radiolytic damage of thymine and thymidine to establish a formidable research group dealing with the chemistry and biochemistry of oxidatively generated, radiation- and photo-induced damage to DNA. 2 Wagner, J. R. and J. Cadet (2010) Oxidation reactions of cytosine DNA components by hydroxyl radical and one-electron oxidants in aerated aqueous solutions. These and numerous other studies by the Grenoble group stimulated the profiling of oxidation products by various oxidants, the quest for guanine oxidation products and the extension to oligonucleotides and DNA repair studies (7-9). [Extracted from the article]

TAUTOMERISM, CHALCONES, ORGANIC chemistry, HYDROGEN bonding, HYDROGEN, INTRAMOLECULAR forces, and ISOMERS

Condensation of 1- or 2-indanones and 1,3-indandiones with aromatic or heteroaromatic carbaldehydes gives products that demonstrate various transformations and effects of general interest for organic chemistry. In the present review, phenomena such as tautomerism, E / Z -isomerization, π-conjugation, hydrogen bonding, and homo- and heteroassociation are considered. The relative stability of various isomers of cyclic chalcones is shown to be determined by the intramolecular hydrogen bonding in their molecules and the formation of associates. The same effects also result in the formation of unusual, otherwise unstable tautomers, such as 2 H -indazoles. The hydrogen bonding-assisted keto-enol and E / Z -isomerization are analyzed. A novel, specific type of conjugation for the studied compounds was proposed and termed "roundabout" conjugation. The bibliography includes 101 references. [ABSTRACT FROM AUTHOR]

DISSOLVED organic matter, ION mobility spectroscopy, ION cyclotron resonance spectrometry, ORGANIC chemistry, TIME-of-flight mass spectrometry, and EUTROPHICATION

• Eutrophication shaped DOM chemistry to a more aliphatic signature with lower isomeric complexity. • Eutrophication induced production of a red-shifted humic-like fluorescence. • This red-shifted humic-like fluorescence carries an aliphatic molecular signature. • Reed marsh introduced unique highly aromatic compounds to connected rivers. • Optical and molecular techniques are complimentary for DOM cycling study in coastal environments. Dissolved organic matter (DOM) plays a crucial role in the coastal carbon cycle. However, eutrophication-induced algal blooms and lateral transport from connected tidal marshes may significantly affect DOM cycling, which remains poorly understood. By combining a suite of bulk and optical techniques, and the Fourier transform ion cyclotron resonance mass spectrometry and ion mobility quadrupole time-of-flight mass spectrometry, we determined DOM concentration and composition along two typical river-estuary transects (namely Liao and Daliao rivers), Northeast China, with contrasting eutrophic state and distribution of tidal marshes. The Daliao River is characterized by a higher eutrophication degree and is surrounded with lower reed coverage than the Liao River. Compared to the Liao River, significantly higher dissolved organic carbon concentrations were observed in the Daliao River, where higher stable carbon isotope (δ13C) values and protein-like fluorescent components, characterized relatively higher autochthonous DOM. Further molecular analysis revealed higher peptide and sugar-like compounds but lower isomeric percentages of several molecular formulas in the Daliao River, suggesting higher molecular lability but lower isomeric complexity than the Liao River. Associations between optical and molecular signatures among all DOM samples revealed that a red-shifted humic-like C3 component was significantly correlated with molecular formulas with lower molecular weight and aromaticity, and higher H/C, indicating that C3 was likely a result of phytoplankton production coupled with further heterotrophic processing. Moreover, we found that reed marshes could introduce to both rivers a series of carboxylic-rich alicyclic compounds, highly unsaturated compounds, and polyphenols with high molecular weight and low H/C. This study suggests that eutrophication and reed marsh affect the DOM quality and can be a potential source of recalcitrant DOM compounds to coastal rivers and estuaries, which warrants further investigations considering the increasing worldwide eutrophication and sea-level rise in coastal delta environments. [Display omitted] [ABSTRACT FROM AUTHOR]

DENSITY functionals, ORGANIC chemistry, and CHEMICAL reactions

In this Communication, we assess a panel of 18 double-hybrid density functionals for the modeling of the thermochemical and kinetic properties of an extended dataset of 449 organic chemistry reactions belonging to the BH9 database. We show that most of DHs provide a statistically robust performance to model barrier height and reaction energies in reaching the "chemical accuracy." In particular, we show that nonempirical DHs, such as PBE0-DH and PBE-QIDH, or minimally parameterized alternatives, such as ωB2PLYP and B2K-PLYP, succeed to accurately model both properties in a balanced fashion. We demonstrate, however, that parameterized approaches, such as ωB97X-2 or DSD-like DHs, are more biased to only one of both properties. [ABSTRACT FROM AUTHOR]

ORGANIC compounds, ORGANIC chemistry, COMPLEX compounds, PHOSPHINE oxides, ALDEHYDES, and PENTANE

[Display omitted] H-phosphonates, H-phosphinates and secondary phosphine oxides are versatile reagents for the construction of complex phosphoryl compounds. Their decade advances in three-component reactions were recorded in this article. Reactions with bicyclo[1.1.1]pentane, alkenes, alkynes, aldehydes, imines, S, Se, et al will be discussed. In this review, we systematically summarized the applications of these P(O)-H compounds in organic synthetic chemistry, and their mechanisms were also discussed. [ABSTRACT FROM AUTHOR]

WOMEN'S volleyball and ORGANIC chemistry

WOMEN'S volleyball and ORGANIC chemistry

BORANES, CATALYSTS, ORGANIC chemistry, CHEMICAL reactions, ALIPHATIC alcohols, GLYCOLS, and HIGH temperatures

Epoxide ring-opening is a key reaction in organic chemistry. We have previously shown that B(C 6 F 5) 3 , a strongly Lewis acidic arylborane, exhibited high rates and unusual selectivities for catalyzing the ring-opening of aliphatic epoxides with alcohols. Here we compare catalysts of the form B(C 6 H 5−X F X) 3 (x = 5, 4, 3, and 0) and determine that moderately Lewis acidic arylboranes have higher regioselectivity, but slower rates in this reaction. At high temperatures, these arylboranes can also hydrolyze into inactive species. However, deactivation is suppressed in the presence of co-catalytic amounts of 1,2-propanediol, and DFT calculations suggest a role for arylborane-H 2 O-diol complexes. Thermal stabilization and regioselectivity enhancement by diol are both more pronounced for B(C 6 F 5) 3 than for less Lewis acidic B(C 6 HF 4) 3 and B(C 6 H 2 F 3) 3 catalysts. These results further demonstrate the catalytic relevance of H-bound networks of arylboranes and diols and enable their use at higher temperatures and greatly increased rates. [Display omitted] • Arylborane catalysts hydrolyze above 90 oC, which decreases rates and selectivity in epoxide ring-opening. • Co-catalytic glycol stabilizes the catalyst against hydrolytic decomposition for > 1 h, while also increasing selectivity. • Glycol-mediated stabilization is higher for more Lewis acidic catalysts such as tris(pentafluorophenyl)borane. [ABSTRACT FROM AUTHOR]