Search

The quest for polymers that would be at the same time bio‐based and degradable after usage, in addition to offering chemical post‐modification options, remains a daunting challenge in contemporary polymer science. Despite advances in polymer chemistry, attempts at controlling the chain‐growth polymerization of muconate esters remain unexplored. Here we show that dialkyl muconates can be rapidly polymerized by organocatalyzed group transfer polymerization (O‐GTP). O‐GTP is conducted to completion at room temperature in toluene within a few minutes, using 1‐ethoxy‐1‐(trimethylsiloxy)‐1,3‐butadiene (ETSB) as initiator and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)‐phosphoranylidenamino]‐2λ ${\lambda }$ 5,4λ ${\lambda }$ 5 catenadi(phosphazene) (P4‐t‐Bu) as catalyst. Chain extension experiments and synthesis of all muconate‐type block copolymers can also be achieved. Furthermore, polymuconates are amenable to facile post‐polymerization modification reactions. This is showcased through the hydrolysis of the ester side chains leading to well‐defined poly(muconic acid), and by epoxidation of the C=C double bonds of the main chain. Last but not least, these internal alkene groups can be selectively cleaved by ozonolysis, demonstrating the upcyclability of polymuconates under oxidative conditions. This work demonstrates that polymuconates constitute a unique platform of bio‐based polymers, easily modifiable in addition to being chemically degradable under user friendly experimental conditions. [ABSTRACT FROM AUTHOR]

A series of compounds with the general formula A2MB2O6 (A=Zn, Ba, Pb; B=Pb, Ba, Zn, Cu) related to the kotoite structure has been prepared employing high‐temperature solid state methods. The substitution of transition elements in place of Zn2+ ions resulted in colored compounds. The optical absorption spectra could be explained based on Tanabe‐Sugano diagram and allowed d‐d transitions. Dielectric studies on Ba2ZnB2O6, (Ba1.5Pb0.5)ZnB2O6, PbZn2B2O6, Pb1.5Zn1.5B2O6, BaZn2B2O6 and Pb2CuB2O6 at room temperature indicate reasonable values at low frequencies, which decrease on increasing frequencies. Magnetic study of synthesized single‐phase compounds BaZnCoB2O6 and Pb2CuB2O6 have been performed. The substitution of Eu3+, Tb3+ and Tm3+ in place of Ba2+ in Ba2ZnB2O6, gives rise to the expected emission of red, green and blue colors. Suitable modifications of the different phosphors in Ba2ZnB2O6, resulted in white‐light emission in Ba2ZnB2O6. The Pb2CuB2O6 compound was found to be a good catalyst in the ipso‐hydroxylation of arylboronic acids. [ABSTRACT FROM AUTHOR]

A two-step synthetic experiment to produce paracetamol from 4-hydroxyacetophenone was designed for undergraduate organic chemistry courses. The experiment begins with the condensation of 4-hydroxyacetophenone with hydroxylamine to form 4-hydroxyacetophenone oxime. This oxime then undergoes a Beckmann rearrangement catalyzed by cyanuric chloride to yield paracetamol. The experiment incorporates several essential organic laboratory techniques, such as reflux, extraction, drying, filtration, rotary evaporation, thin-layer chromatography, and column chromatography, providing students with comprehensive training in organic synthesis. By synthesizing a compound of significant medical and economic value, the experiment demonstrates practical applications of organic synthesis, thereby enhancing student interest in organic chemistry. Additionally, the use of a small molecule organic catalyst for the Beckmann rearrangement deepens students’ understanding of the principles of organic catalysis and the mechanism of the Beckmann rearrangement. [ABSTRACT FROM AUTHOR]

Fixation of carbon dioxide is a key issue for the sustainable synthesis of chemical compounds. A catalyst system for the preparation of cyclic carbonates by the fixation of carbon dioxide (CO2) onto epoxides is presented. This system is designed for easy application due to the availability of the compounds on an industrial scale as well as moderate reaction conditions. Notably, it avoids the use of metal-halogen catalysts and instead employs a tertiary amine as the catalytic center, in conjunction with an alcohol acting as a hydrogen bond donor (HBD). The kinetics of the cycloaddition reaction between epoxides and CO2 were thoroughly investigated using IR spectroscopy. Remarkably, optimization of the amino-to-alcohol group ratio and the amine structure was carried out to enhance the overall performance of the catalyst system showing a synergistic effect between the tertiary amine and the hydroxyl. Most notably, this entire process is conducted without the use of solvents and operates at ambient pressure, underscoring its significant ecological advantages.

In this research, a mild, efficient, and general method has been developed to synthesize the new derivatives of 2-aryl/alkyl-3H-indol-3-ones in moderate to excellent yields. This method allowed the syntheses of these compounds via the three-component reaction of anhydride compound, sodium cyanide, and aniline derivatives using acetic anhydride as an organic catalyst in one-pot reactions. The advantages of this method include mild reaction conditions, simple procedures, and easy workup. [ABSTRACT FROM AUTHOR]

This manuscript presents a regioselective chlorination of arenes, yielding almost exclusively the monochlorinated product. It tolerates free hydroxy groups, 1°, 2° and 3° amines, and carboxylic acids, among other polar and nonpolar functional groups, as well as mono‐ and polysubstituted aromatic rings. Additionally, the utilization of chlorosulfonium salts as the chlorinating agent is demonstrated. The method emerges as an alternative to other processes where organic byproducts must be separated from the reaction mixture. In addition, the main byproducts are gaseous materials such as CO and CO2. This publication introduces the application of sulfoxides, oxalyl chloride, and aqueous hydrogen peroxide as the chlorination mixture. [ABSTRACT FROM AUTHOR]

Pyrimido[5,4‐d]pyrimidines are biologically important compounds with diverse activity depending on the substituent groups around the heterocycle. The 3,4‐dihydropyrimido[5,4‐d]pyrimidines are efficiently converted to the aromatic derivatives by Dimroth rearrangement promoted by reaction with piperidine, in a very slow process. Subsequently, the aromatic derivatives are converted to new 4,8‐disubstituted‐pyrimido[5,4‐d]pyrimidine derivatives by reaction with aldehydes in an acidic medium. The 4,8‐disubstituted‐pyrimido[5,4‐d]pyrimidines are also obtained much more efficiently by a tandem reaction between the 3,4‐dihydropyrimido[5,4‐d]pyrimidines, piperidine and a variety of aldehydes. The cascade reaction approach has a broad application since phenyl, haloaryl, alkoxy‐aryl, hydroxy‐aryl, and heteroaryl aldehydes are compatible with the reaction conditions. The reactions were studied by 1H NMR. These studies support the reaction mechanisms proposals. The tandem approach involves the formation of ionic reactive intermediates that allows explain this approach's efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] Covalent organic frameworks (COFs) are excellent candidates for rationally designed metal-coordinated catalysts due to their porous structures and adjustable organic building blocks. In this work, a two-dimensional (2D) COF with novel fxt topology was synthesized. The newly devised COF had been fully characterized by a range of spectroscopic and microscopic techniques. The COF was further metallized by the gold species to form a heterogeneous catalyst that enabled the one-pot synthesis of flavone and its derivatives. The Au@COF catalyst showed high catalytic activity and good recyclability. This work demonstrates the great potential of metallized COFs with unique well-defined pores in organic catalysis. [ABSTRACT FROM AUTHOR]

In this work, the organocatalytic strategy for the ring‐opening copolymerization (ROCOP) of 3,5‐anhydro‐D‐xylose oxetane 1 and various anhydrides has been demonstrated by use of phosphazene base (P1) and triethyl borane (TEB). The ROCOP proceeds efficiently to generate sugar‐derived polyesters with perfectly alternating sequence distribution, controlled molar masses, and moderate dispersity. These polyesters show good thermal stability (Tmax > 320°C) and adjustable glass transition temperatures (Tg 70 ~ 110°C) with the variation of anhydrides. This work provides efficient organocatalyst for the selective copolymerization for biomass‐derived degradable polyesters. [ABSTRACT FROM AUTHOR]

A procedure was developed for preparing block synthons by the reaction of 2,4-pentanedione, 1,2-ethanedithiol, and aromatic aldehydes in the presence of an organic catalyst (triethylamine, piperidine, diazabicycloundecene, morpholine) to construct heterocycles derived from bis(arylmethylsulfanyl diketones). Among the bis(sulfanyl diketones) prepared, the compounds containing p-methoxyphenyl and thienyl substituents in the methinesulfanyl moiety showed the highest fungicidal activity toward phytopathogenic fungi Bipolaris sorokiniana, Fusarium oxysporum, and Rhizoctonia solani. [ABSTRACT FROM AUTHOR]

Organometallic catalyst can make chemical reaction achieve high selectivity, high yield, mild reaction conditions, simple and convenient operation. Among them, N-heterocyclic carbenes (NHCs) is a kind of ligand with strong stability, low price, low toxicity and easy preparation. The strong coordination ability of nitroheterocyclic carbens with transition metals has led to its rapid development as a new ligand of transition metal complexes. Compared with other metals, metal Cu stands out among many metals due to its advantages of low price and abundant reserves. Taking nitrogen heterocyclic carben-copper complex(NHC-Cu) as an example, this paper summarized and summarized the research progress of NHC-Cu as catalyst in organic reaction in recent ten years. It mainly includes Click reaction (azide and alkyne cycloaddition reaction),addition of terminal alkynes to trifluoromethyl ketone, conjugate addition reaction, carbonylation, asymmetric allyl substitution, A~3 coupling reaction, boriding and oxidation reaction [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis and polymerization performances of terpenoid‐derived camphoric anhydride (CA). Utilizing simple organo‐base tBuP2 as the catalyst, CA can polymerize with various epoxides by efficient and controlled ring‐opening alternating copolymerization (ROAC) to afford perfectly alternating poly(CA‐alt‐epoxide). Kinetic study shows that the polymerization proceeds following zero‐order dependence on the concentration of CA. The self‐switchable terpolymerization from the mixture of CA, propylene oxide (PO) and ε‐caprolactone (CL) is conducted under the catalysis of tBuP2. First, ROAC of CA and PO is carried out exclusively with benzyl alcohol as initiator. Then, block copolymer (BCP) poly(CA‐alt‐PO)‐b‐PCL is obtained via the sequential polymerizations after the complete consumption of CA. The followed ring‐opening polymerization (ROP) of CL is initiated by the terminal hydroxyl of the ROAC‐resulted poly(CA‐alt‐PO) polyester without external stimulus. During the process, the excess PO compound remains intact. The one‐pot synthesis displays distinct living nature and perfect chemoselectivity. The as‐prepared terpenoid‐derived alternating and BCP's exhibit elevated thermal properties. [ABSTRACT FROM AUTHOR]

In order to apply the C-H activation strategy to the development of chiral organic catalysts, two novel C3-trimethylsilyl substituted chiral proline catalysts are designed and synthesized using L-proline as the starting material and C(sp 3)-H silylation as the key step, which are applied to the asymmetric aldol reaction of p-nitrobenzaldehyde with acetone and the asymmetric Mannich reaction of imine with β-methylbutyraldehyde, respectively. Both target products can be synthesized with a good enantioselectivity. This strategy effectively enriches the means of structural modification of proline and provids a new method for the development of new silicon-containing organic catalysts.

In order to apply the C-H activation strategy to the synthesis of novel organic catalysts, a novel primary amine-thiourea catalyst is designed and synthesized by using the developed inert C(sp3)-H amination method as a key step. First, using phenylalanine as the substrate and di-tert-butyl-azodicarboxylic acid as the nitrogen source, the corresponding amination products are obtained by employing the Pd-catalyzed inert C(sp3)-H amination method. Next, the chiral skeleton of 1,2-diamine privileged in organocatalysts is obtained by simple conversion. Then, a novel chiral primary amine-thiourea bifunctional organic catalyst is synthesized, whose structure is characterized by nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS). The synthesized catalyst is also successfully applied to the asymmetric Michael addition reaction of isobutyraldehyde with nitroolefins. Due to the advantages of transition metal-catalyzed C-H activation, such as simplicity, high efficiency, high atomic economy, and non pre-functionalization, its application to the development of small molecular catalysts will undoubtedly make the structure of catalyst more diversified and the synthesis process more efficient.

Chiral benzothiazepines constitute the core structures of many foremost pharmaceuticals with diverse biological activities endowed by their unique scaffolds, which poses a great challenge to organic chemists and pharmaceutical researchers. This review provides a concise overview for the asymmetric synthesis of chiral benzothiazepine derivatives, focusing on advances in asymmetric catalysis, including metal catalysis, small-molecule organocatalysis and enzymatic catalysis. The catalytic asymmetric reactions, involving asymmetric epoxidation, reduction, dihydroxylation, hydrogenation, aldol reaction and other sulfa-Michael addition, have emerged as powerful strategies for the rapid construction of chiral benzothiazepine through single or multistep reactions. The booming asymmetric synthetic methodology affords us instructive clues for the highly efficient preparation of chiral benzothiazepines, facilitating their large-scale preparation and diversity-oriented synthesis.

Noble-metal nanoparticles are regarded as one of the most promising catalysts to reduce the organic pollutant 4-nitrophenol (4-NP). However, the inevitable agglomeration of noble-metal nanoparticles and their poor distributions in catalytic systems limit their performance. Here, we propose a strategy to encapsulate Au nanoparticles inside porous organic cages (POCs) of soluble RCC3 and stabilize the size of Au nanoparticles at ∼3.25 nm. Typically, the Au@RCC3 composite exhibits excellent 4-NP catalytic reduction performance, which is superior to the corresponding Au bulk catalyst and is also closely related to the size of Au nanoparticles. The normalized X-ray absorption near-edge structure (XANES) results indicate that the electron deficiency at the Au atoms in Au@RCC3 is due to the existence of the RCC3 cage, which is beneficial to accelerate the electron transfer from BH4– to 4-NP during the hydrogenation process. This is also shown by density functional theory (DFT), in which a low energy barrier of 1.03 eV exists for the Au12 cluster compared with 1.37 eV for the Au25 cluster. Therefore, the encapsulation of noble-metal nanoparticles with soluble POCs is an effective way to design and develop stable active catalysts rationally. [ABSTRACT FROM AUTHOR]

The ability of chalcogenium salts to transfer an electrophilic moiety to a given nucleophile is well known. However, up to date, these reagents have been used in stoichiometric quantities, producing a substantial amount of waste as byproducts of the reaction. In this report, we disclose further investigation of selenonium salts as S‐adenosyl‐L‐methionine (SAM) surrogates for the alkylation of nucleophiles in aqueous solutions. Most importantly, we were able to convert the stoichiometric process to a catalytic system employing as little as 10 mol % of selenides to accelerate the reaction between benzyl bromide and other alkylating agents with sodium cyanide in water. Probe experiments including 77Se NMR and HRMS of the reaction mixture have unequivocally shown the presence of the selenonium salt in the reaction mixture. [ABSTRACT FROM AUTHOR]

February 2021 marked the 160th anniversary of the birth of N.D. Zelinskii, who worked for more than 50 years at Moscow University and headed a large school of organic chemists. The present historical sketch of the life and scientific achievements of Nikolai Zelinskii highlights his contribution to the development of catalysis, petroleum chemistry, and hydrocarbon chemistry, as well as the wide range of his interests in the field of organic chemistry. [ABSTRACT FROM AUTHOR]

Several N-isopropyliodobenzamides were evaluated as catalysts for the oxidation of benzhydrol to benzophenone in the presence of Oxone® (2KHSO5·KHSO4·K2SO4) as a co-oxidant at room temperature. A study on the substituent effect of the benzene ring of N-isopropyl-2-iodobenzamide on the oxidation revealed that its reactivity increased in the following order of substitution: 5-NO2 < 5-CO2Me, 3-OMe < 5-OAc < 5-Cl < H, 4-OMe < 5-Me < 5-OMe. The oxidation of various benzylic and aliphatic alcohols using a catalytic amount of the most reactive 5-methoxy derivative successfully resulted in moderate to excellent yields of the corresponding carbonyl compounds. The high reactivity of the 5-methoxy derivative at room temperature is a result of the rapid generation of the pentavalent species from the trivalent species during the reaction. 5-Methoxy-2-iodobenzamide would be an efficient and environmentally benign catalyst for the oxidation of alcohols, especially benzylic alcohols.

The enantioselective synthesis of chiral N,N‐acetals derived from α‐dicarbonyl compounds has been achieved. Good yields and enantioselectivities were observed for the reaction with various α‐dicarbonyl compounds with 2‐aminobenzamides using chiral bis(imidazoline)‐phosphoric acid catalysts. Based on these experimental investigations, a possible transition state is proposed to explain the origin of the asymmetric induction. [ABSTRACT FROM AUTHOR]

Supported ionic liquid catalysts have gained significant attention in recent years to overcome the limitations of the homogeneous and heterogeneous catalysis. The thin film containing dispersed homogeneous catalyst in the ionic liquid have been immobilized onto various porous solid supports having a high surface area to synthesize supported ionic liquids (SILs) that acted as potential organocatalysts in organic green synthesis. Support materials, ionic liquids, and molecularly dispersed catalysts have played a significant role in increasing the catalytic activity of the SIL catalysts. In the present review, the literature of the last decade concerning the synthesis of SIL catalysts by using different strategies as well as their applications in organic synthesis is incorporated. The main emphasis of the present work is to critically analyze the recent developments in the supported molecular dispersed catalysts (such as lewis acids, organometallic complexes, metal nanoparticles, and chemical functionality associated with cation/anion of ionic liquids) using ILs and explore their potential to act as building block systems in catalysis. [ABSTRACT FROM AUTHOR]

Imidazoline is an important class of compounds found in numerous natural and pharmaceutical products. The compounds are also used as an intermediate in the synthesis of organic molecules. Moreover, chiral imidazolines are widely utilized as organocatalysts to synthesize various natural and synthetic organic compounds. In the past decade, there was an increase in interest in developing new methods to synthesize these imidazoline analogs. Both modification of the previously established methods and the development of new methods are carried out significantly. This review article highlights the progress of the synthesis of imidazoline scaffolds in the last few years (2009‐present). The review also described the proposed mechanism illustrated in many of the reports. [ABSTRACT FROM AUTHOR]

Herein, a volcanic-based mesoporous catalytic system is precisely characterized by various analytical methods and suitably used for facilitating the organic synthesis reactions. Briefly, high reaction yield (99%) has been obtained in short reaction times (4 min) in the synthesis reactions of chromene pharmaceutical derivatives, through applying this highly efficient organometallic catalyst. From mechanistic aspect, effective electronic interactions between heteroatoms like oxygen with the surface of pumice microparticles provide a suitable condition for covalent bindings. As the main advantages of the volcanic pumice, high catalytic performance after activation of the chemical functional groups via acid treatment, magnetic property, and completely natural basis (biocompatibility and biodegradability) could be referred. Highly porous structure leads reactants to be entrapped in the tiny pores and activated for covalent binding. Moreover, significant convenience in the separation of the particles and great reusability could be mentioned as additional excellences for this catalyst. [ABSTRACT FROM AUTHOR]

Asymmetric functionalizations of α‐sulfanyl cyclic ketones were realized via chiral phosphoric acid catalyzed enantioselective addition reactions with aldimines, azodicarboxylates and allenamides. A series of chiral organosulfur compounds possessing sulfur‐containing tetrasubstituted stereocenters were accessed via these methods, with excellent regioselectivities and high stereoselectivities. [ABSTRACT FROM AUTHOR]

This work introduces a new additive named 4,4’-trimethylenedipiperidine for the practical and ecofriendly preparation of ethyl 5-amino-7-(4-phenyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate derivatives. This chemical is commercially available and easy to handle. It also possesses a low melting point and a broad liquid range temperature, high thermal stability, and good solubility in water. Based on green chemistry principles, the reaction was performed in a) a mixture of green solvents i.e. water and ethanol (1:1 v/v) at reflux temperature, and b) the additive was liquefied at 65 °C and the reaction was conducted in the liquid state of the additive. High yields of the desired triazolo-pyrimidines were obtained under both aforementioned conditions. Our results demonstrated that this additive, containing 2 Lewis base sites and able to act as an acceptor-donor hydrogen bonding group, is a novel and efficient alternative to piperidine, owing to its unique properties such as its reduced toxicity, nonflammable nature, nonvolatile state, broad liquid range temperature, high thermal stability, and ability to be safely handled. Furthermore, this additive could be completely recovered and exhibited high recyclability without any change in its chemical structure and no significant reduction in its activity. The current methodology has several advantages: (a) it avoids the use of hazardous materials, as well as toxic, volatile, and flammable solvents, (b) it does not entail tedious processes, harsh conditions, and the multistep preparation of catalysts, (c) it uses a metal-free and noncorrosive catalyst, and (d) reduces the generation of hazardous waste and simple work-up processes. The most important result of this study is that 4,4’-trimethylenedipiperidine can be a promising alternative for toxic, volatile, and flammable base reagents in organic synthesis owing to its unique properties. [ABSTRACT FROM AUTHOR]

The isochroman scaffold constitutes an important structural unit, which is present in various bioactive natural products and synthetic pharmaceutical compounds exhibiting wide arrays of biological properties. Hence the synthesis of this class of heterocyclic compounds in a stereoselective fashion is highly significant and desirable. In the last decade, a substantial advancement has been witnessed ln the catalytic asymmetric synthesis of isochroman derivatives by employing metal catalysts bearing chiral ligands or by chiral metal‐free organocatalysts. This review aims to provide an overview of the transition metal‐catalyzed and organocatalyzed asymmetric syntheses of isochroman derivatives including isochromenes and isochromanones. [ABSTRACT FROM AUTHOR]

The bifunctional quinine‐catalyzed stepwise (3+2) cycloaddition for the enantioselective construction of spirooxindole‐fused cyclopenta[c]chromen‐4‐ones is developed. The reactions of 3‐homoacylcoumarins and alkylidene oxindole electrophiles generate aforementioned spirooxindole‐chromenone adducts bearing five contiguous stereocenters, of which one is the spiro all‐carbon quaternary stereocenter in high yields (up to 99%) with excellent stereoselectivities (up to >20:1 dr and 99% ee). This methodology was investigated for three different alkylidene oxindole electrophiles and could also be practically demonstrated on a gram scale. Mechanistic investigations revealed that the (3+2) cycloaddition for the enantioselective synthesis of spirooxindole‐fused cyclopenta[c]chromen‐4‐ones is proceeding via a stepwise reaction pathway. [ABSTRACT FROM AUTHOR]

The enantioselective allylation of simple aldimines has been studied making use of density functional theory calculations. The proposed reaction mechanism includes eight possible transition-state structures, four of them leading to the R and four to the S enantiomer, respectively. Despite the fact that this multiple transition-state problem depends on subtle effects, all density functionals and basis sets employed indicate that the R isomer is favourably formed in contradiction to earlier published experimental results. The discussion of the transition-state structures and the comparison with literature results give insight into the origin of the observed stereoselectivity. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Δ2‐Pyrrolin‐4‐ones undergo organocatalyzed sulfa‐Michael/aldol domino spirocyclizations with mercaptoacetaldehyde dimer. The products contain three contiguous stereocenters (ee up to 99%, dr up to 95:5, 25 examples) and can be transformed into analogues of natural products. With the use of a single catalyst, the absolute configuration of the products were determined by the configuration of the exocyclic double bond of the starting material. These results point at the possibility of a widespread use of unsaturated Δ2‐pyrrolin‐4‐ones in various (organo)catalyzed (cascade) transformations for accessing libraries of 3D‐rich pyrrolone‐based (spiro)heterocycles. [ABSTRACT FROM AUTHOR]

Carbohydrates are the most prevalent class of naturally occurring biomolecules. They mediate cell signaling, bacterial virulence, and metabolism, among other functions. The site‐selective functionalization of carbohydrates has been a long‐standing problem in chemistry. Phosphoramidates are a particularly challenging functional group to install stereoselectively because of the chirality at the phosphorus center. As such, the site‐ and stereoselective phosphoramidation of carbohydrates has never been achieved. We have developed the first site‐ and stereoselective phosphoramidation reaction of carbohydrates using a chiral catalyst and a chiral electrophile. This method offers a convenient solution for the selective synthesis of phosphoramidated carbohydrate‐containing prodrugs and natural products. [ABSTRACT FROM AUTHOR]

An iridium(III)‐catalyzed three‐component reaction of enamides, aryldiazonium tetrafluoroborates, and 1,4‐diazabicyclo[2.2.2]octane bis(sulfur dioxide) (DABSO) for the direct C(sp2)−H arylsulfonylation of enamides is developed. This transformation provides a robust and straightforward approach for preparing a diverse array of β‐amidovinyl sulfones in moderate to excellent yields and high stereoselectivities without Light‐emitting diode (LED) radiation. This transformation also features mild conditions, broad substrate scopes, and excellent functional group tolerance. [ABSTRACT FROM AUTHOR]

• TBD in conjunction with thiols induced living ROP of carbazole-containing thiiranes. • Linear and star-shaped polymers with relatively low polydispersity were prepared. • Synthesized polymers are promising host materials for solution processable PLED s. The anionic ring-opening polymerization of carbazole-containing monomers, (9-carbazolylmethyl)thiirane (M1) and (3,6-di- tert -butyl-9-carbazolylmethyl)thiirane (M2), with hexanethiol or pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) as initiators and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst at 20 °C in tetrahydrofuran or N,N-dimethylformamide as solvents has been studied. The polymerization of these monomers proceeds in a living fashion affording linear and star-shaped polymers with controlled molecular weight (M n = 4000–15,000 g mol−1) and relatively low polydispersity (Đ < 1.3). It was demonstrated that end-capping of polymers by trifluoroacetic anhydride allowed to protect thiol end groups from oxidative coupling, which typically leads to the broadening of molecular weight distribution of the synthesized polymers. The thermal, photophysical and electrochemical properties of the synthesized linear and star-shaped polymers were estimated. [ABSTRACT FROM AUTHOR]

C5‐disubstituted Meldrum's acid precursors were shown to be a useful platform for the synthesis of an array of 3‐alkylated dihydrocoumarins with up to 93:7 er, thanks to an enantioselective domino cyclization‐decarboxylative‐protonation reaction triggered by an unprecedented benzhydryl‐derived cupreine organocatalyst. This cyclization sequence was extended to an emerging organocatalytic decarboxylative‐chlorination reaction in the presence of trichloroquinolinone and by means of a bifunctional cinchona derived Brønsted base which gave rise to the formation of dihydrocoumarins (up to 79:21 er) with a tertiary chlorinated stereocenter. [ABSTRACT FROM AUTHOR]

A pharmacophore model for inhibitors of Escherichia coli’s DNA Gyrase B was developed, using computer-aided drug design. Subsequently, docking studies showed that 2,5(6)-substituted benzimidazole derivatives are promising molecules, as they possess key hydrogen bond donor/acceptor groups for an efficient interaction with this bacterial target. Furthermore, 5(6)-bromo-2-(2-nitrophenyl)-1H-benzimidazole, selected as a core molecule, was prepared on a multi-gram scale through condensation of 4-bromo-1,2-diaminobenzene with 2-nitrobenzaldehyde using a sustainable approach. The challenging functionalization of the 5(6)-position was carried out via palladium-catalyzed Suzuki–Miyaura and Buchwald-Hartwig amination cross-coupling reactions between N-protected-5-bromo-2-nitrophenyl-benzimidazole and aryl boronic acids or sulfonylanilines, with yields up to 81%. The final designed molecules (2-(aminophen-2-yl)-5(6)-substituted-1H-benzimidazoles), which encompass the appropriate functional groups in the 5(6)-position according to the pharmacophore model, were obtained in yields up to 91% after acid-mediated N-boc deprotection followed by Pd-catalyzed hydrogenation. These groups are predicted to favor interactions with DNA gyrase B residues Asn46, Asp73, and Asp173, aiming to promote an inhibitory effect.

[4-Iodo-3-(isopropylcarbamoyl)phenoxy]acetic acid was developed as a highly reactive and easily separable catalyst for the oxidative cleavage of tetrahydrofuran-2-methanols to γ-lactones in the presence of Oxone® (2KHSO5·KHSO4·K2SO4) as the co-oxidant. The reactivity of this new catalyst was considerably greater than that of our previously reported catalyst, 2-iodo-N-isopropylbenzamide. The new catalyst and product were easily separated by only liquid-liquid separation without chromatography. In addition, using a mixture of nitromethane and N,N-dimethylformamide as the solvent and heating enabled a low catalyst loading, a short reaction time, and high product yield. Oxidative cleavage using the new catalyst can be used as a practical and efficient method for synthesizing γ-lactones. [ABSTRACT FROM AUTHOR]

Abstract: A new family of polystyrene‐supported cis‐4‐hydroxydiphenylprolinol silyl ethers has been prepared, and the resulting polymers have been evaluated as organocatalysts to promote the tandem reaction between N‐protected hydroxylamines and α,β‐unsaturated aldehydes in batch and flow. The new PS‐supported catalysts compare favorably with well‐established immobilized Jørgensen‐Hayashi catalysts, affording 5‐hydroxyisoxazolidines as single diastereoisomers with high enantioselectivities and good yields (up to 83% yield, up to 99% ee). [ABSTRACT FROM AUTHOR]

Optically pure hetero-organic organocatalysts, bearing a hydroxy moiety, a stereogenic sulfinyl group and a chiral amine moiety, have revealed high catalytic activity in the asymmetric reduction of various N-aryl ketimines leading to the corresponding chiral amines. Desired products were formed in high chemical yields (up to 95%) and with ee’s up to 97%. The influence of particular stereogenic centres on the stereochemical outcome of the reduction reaction is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Metal‐free carbonitride(CN) semiconductors are appealing light‐transducers for photocatalytic redox reactions owing to the unique band gap and stability. To harness solar energy efficiently, CN catalysts that are active over a wider range of the visible spectrum are desired. Now a photochemical approach has been used to prepare a new‐type triazine‐based CN structure. The obtained CN shows extraordinary light‐harvesting characteristics, with suitable semiconductor‐redox potentials. The light absorption edge of the CN reaches up to 735 nm, which is significantly longer than that of the conventional CN semiconductor at about 460 nm. As expected, the CN can efficiently catalyze oxidation of alcohols and reduction of CO2 with visible light, even under red‐light irradiation. The results represent an important step toward the development of red‐light‐responsive triazine‐based structures for solar applications. [ABSTRACT FROM AUTHOR]

Abstract: A metal‐free, convenient photocatalytic approach to chalcones from β‐nitrostyrenes and benzaldehydes via a radical denitrative benzoylation pathway is reported. The salient features of the protocol include the utilization of visible light as an inexpensive and ecosustainable energy source, N‐hydroxyphthalimide (NHPI) as a reusable organophotocatalyst and acetonitrile as an acceptable green solvent to afford chalcones in excellent yields at room temperature in a one‐pot procedure. Notably, this is the first application of β‐nitrostyrenes as readily available substrates for chalcone synthesis and the first example of photocatalysis in this field. [ABSTRACT FROM AUTHOR]

Abstract: An efficient enantioselective Michael reaction of readily available α‐substituted N‐Boc isoxazolidin‐5‐ones is described under phase transfer conditions with up to 95:5 er. The organocatalytic process is promoted by a low catalytic loading of a commercially available N‐spiro quaternary ammonium salt. This sequence opens an entry to chiral heterocyclic platforms displaying a β‐amino carbonyl motif with an α‐all‐carbon quaternary stereogenic center. The methodology was also successfully extended to the asymmetric amination reaction using an azodicarboxylate electrophile. [ABSTRACT FROM AUTHOR]

Five novel thioureas have been obtained through multi-step reactions from d -Mannitol as starting material and applied as catalysts in the asymmetric Henry reaction. Using catalyst 7a , (1 S ,2 R )-2-nitro-1-phenylpropan-1-ol containing two chiral centers was obtained in high yield and with high selectivity (up to 95% yield, 87% ee, 91:9 dr). This catalyst also retained activity in the presence of water, affording a up to 93% yield, 88% ee, and 94:6 dr. [ABSTRACT FROM AUTHOR]