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Microwaves have been successfully employed in the Lewis acid titanium tetrachloride-assisted synthesis of peptide systems. Dipeptide systems with their amino function differently protected with urethane protecting groups have been synthesized in short periods of time and with high yields. The formation of the peptide bond between the two reacting amino acids was achieved in pyridine by using titanium tetrachloride as a condensing agent and heating the reaction mixture with a microwave reactor. The reaction conditions are compatible with amino acids featuring various side chains and different protecting groups on both the amino function and side chains. Additionally, the substrates retain their chiral integrity after reaction. [ABSTRACT FROM AUTHOR]

In order to solve the problem of the low efficiency of lactose hydrolysis using traditional metal–organic frameworks (MOFs) nanozymes, Brønsted acid active sites (-COOH) were firstly introduced into Fe-MIL-101 nanozymes to enhance the lactose hydrolysis activity of MOFs bearing Lewis acid sites in this study. When compared to Fe-MIL-101, Fe-MIL-101-COOH exhibited improved catalytic performance, showing a lactose conversion rate of up to 78%. Our experiments suggested that this enhancement could be attributed to the synergistic effect between the Brønsted acidic COOH groups and Lewis acidic Fe clusters. Furthermore, Fe-MIL-101-COOH displayed good stability and reusability with no significant loss in catalytic activity observed after at least five consecutive cycles. Our results showed that the activity of Fe-MIL-101-COOH with Brønsted acid active sites was better than that of Fe-MIL-101. Fe-MIL-101-COOH could be applied to the hydrolysis of lactose in milk powder and the conversion rate of lactose was higher than 48%. This study provided support for the application of MOFs nanozymes in lactose catalytic conversion. [ABSTRACT FROM AUTHOR]

The enantioselective introduction of gem‐difluorinated carbonyl (i. e. α,α‐difluoro carbonyl) moieties into organic structures is a synthetically valuable but highly challenging approach. During the past decades, continuous efforts have been made for the developments of synthetic strategies for constructing C(sp3)−CF2COR chiral centers with high levels of enantioselectivities. This review summarizes and discusses the recent advance in the enantioselective construction of gem‐difluorinated carbonyl moieties, which are organized according to the reaction categories. [ABSTRACT FROM AUTHOR]

We report herein an effective method for an iron‐catalyzed vinylogous Michael addition of BODIPY derivatives to para‐quinone methides under mild conditions. The corresponding BODIPY‐derived diarylmethane compounds were obtained in 65–93 % yields. This method is featured by its inexpensive catalyst, simple reaction condition and broad substrate scope. [ABSTRACT FROM AUTHOR]

The report introduces simple yet highly reactive calcium salt, Ca[Al(ORF)4]2 (RF=C(CF3)3), 1, which effectively catalyses olefin hydrosilylation through an unusual mechanism involving the activation of the alkene molecule. Upon dissolution in o‐difluorobenzene (oDFB), 1 forms a highly Lewis acidic [Ca(oDFB)6]2+ complex. Our DFT calculations reveal that fluoride ion affinity is comparable to SbF5. Reactivity tests show that it effectively catalyses the hydrosilylation of olefins with high regioselectivity, also in reactions involving sterically demanding substrates like (iPr)3SiH or tetrasubstituted olefins. Experimental and computational results point to the mechanism where the olefin molecule forms a complex with Ca2+, which significantly facilitates the attack of H‐SiR3 on the C=C double bond. [ABSTRACT FROM AUTHOR]

ABSTRACT The construction of metal–organic frameworks (MOFs) with desirable structures for high‐performance photocatalysis is attractive but remains challenging. Here, a hierarchically meso‐ and microporous scCu‐MOF‐74 was synthesized in supercritical CO2 (scCO2)/methanol solution. Compared with the conventional microporous Cu‐MOF‐74, the meso‐ and microporous scCu‐MOF‐74 has more exposed and accessible Lewis acid sites derived from the missing‐linker defects. The unique structure endows scCu‐MOF‐74 with superior molecular accessibility, enhanced separation, and transfer efficiency of photogenerated charges. High catalytic activity and reusability can be achieved in photo‐oxidative coupling of amines, reaching a maximum N‐benzylbenzaldimine yield rate of 4.80 mmol g−1 h−1 under mild conditions, that is, air atmosphere and room temperature. This study provides a new idea for improving the intrinsic photocatalytic activities of MOFs. [ABSTRACT FROM AUTHOR]

Fluorinated arylborane‐based Lewis acid catalysts have shown remarkable activity and serve as ideal examples of transition metal‐free catalysts for diverse organic transformations. However, their homogeneous nature poses challenges in terms of recyclability and separation from reaction mixtures. This work presents an efficient technique for the heterogenization of boron Lewis acid catalysts by anchoring Piers' borane to allyl‐functionalized iron oxide. This catalyst demonstrates excellent activity in the hydrosilylation of imines and the reductive amination of carbonyls using various silanes as reducing agents under mild reaction conditions. The catalyst exhibits broad tolerance towards a wide range of functional substrates. Furthermore, it exhibits good recyclability and can be easily separated from the products using an external magnetic field. This work represents a significant advance in the development of sustainable heterogenous metal‐free catalysts for organic transformations. [ABSTRACT FROM AUTHOR]

Synthesis of bicyclic scaffolds has gained significant attention in drug discovery due to their potential to mimic benzene bioisosteres. Here, we present a mild and scalable Sc(OTf)3‐catalyzed [3+2] cycloaddition of bicyclo[1.1.0]butanes (BCBs) with ynamides, yielding a diverse array of polysubstituted 2‐amino‐bicyclo[2.1.1]hexenes in good to excellent yields. These products offer valuable starting materials for the construction of novel functionalized bicyclo[1.1.0]butanes. Preliminary mechanistic studies indicate that the reaction involves a nucleophilic addition of ynamides to bicyclo[1.1.0]butanes, followed by an intramolecular cyclization of in situ generated enolate and keteniminium ion. We expect that these findings will encourage utilization of complex bioisosteres and foster further investigation into BCB‐based cycloaddition chemistry. [ABSTRACT FROM AUTHOR]

A porous Sn–Er–Beta zeolite catalyst was rapidly prepared by introducing Sn source with water bath method and Er source with solid-state ion exchange method. When adding 180 mg catalyst, 225 mg glucose and 10 mL water into a reaction kettle at 200 °C for 2 h, the yield of lactic acid can reach 71.2%. After being recycled 5 times, the lactic acid yield of the catalyst can still reach 45.3%. The physical and chemical properties of Sn–Er–Beta zeolite were characterized, and it was confirmed that the catalyst had a multi-stage pore structure, with Sn and Er elements existing in the zeolite skeleton. Among them, the increase of Lewis acidity, Brønsted acidity and special strong alkaline sites of Sn–Er–Beta zeolite caused by the introduction of Sn, and the Lewis acidic sites are further increased after the introduction of Er. The combination of Sn and Er obviously improves the catalyst's capability to catalyze glucose and fructose to produce lactic acid. This provides an important reference value for the directional catalytic process of sugars. [ABSTRACT FROM AUTHOR]

Tris(pentafluoroethyl)indane dihydrate, [In(C2F5)3(OH2)2], and the gallium analog, [Ga(C2F5)3(OH2)2], serve as transfer reagents for the In(C2F5)3 and Ga(C2F5)3 units, as illustrated by the preparation of salts of (pseudo)halogenotris(pentafluoroethyl)indate and ‐gallate anions, [M(C2F5)3)X]− (M=Ga, In; X=F, Cl, Br, I, CN, SCN). Due to the water tolerance and water solubility of [In(C2F5)3(OH2)2] and [Ga(C2F5)3(OH2)2], reactions can be performed in the presence of water or even in an aqueous medium. [ABSTRACT FROM AUTHOR]

This document provides information on the use of photoacid generators (PAGs) in catalysis, specifically in the Friedel-Crafts alkylation of indoles with aldehydes/ketones. The study focuses on diarylethenes and terarylenes as PAGs, which have advantages such as high quantum yields and autonomy. The researchers developed an environmentally friendly method for synthesizing diindolylmethane derivatives with potential antibacterial, antitumor, and antifungal activities. The document also provides detailed information on the synthesis and characterization of various compounds, including their physical properties and spectroscopic data. This information can be useful for researchers studying these compounds and their properties. [Extracted from the article]

This article provides a comprehensive overview of various methods for the synthesis of substituted naphthalene derivatives. Naphthalene is a versatile organic compound with applications in materials chemistry, electronics, and medicine. The synthesis of naphthalene involves metal-catalyzed reactions, such as palladium-catalyzed carboannulation, and yields derivatives with diverse substituents. These derivatives have medicinal importance and exhibit a wide range of therapeutic activities. The article discusses different metal-catalyzed reactions, their mechanisms, and examples of reactions. It also highlights the need for more environmentally friendly approaches to naphthalene synthesis. [Extracted from the article]

A new strategy for the synthesis of 3‐substituted phthalides has been developed via a Lewis acid‐catalyzed intramolecular ring opening of aziridines with esters. Broad substrate scope, good yields and mild conditions made the cyclization reaction very suitable for the rapid construction of libraries of 3‐substituted phthalide compounds. [ABSTRACT FROM AUTHOR]

Inverse hydride shuttle catalysis provides a multicomponent platform for the highly efficient synthesis of alkaloid frameworks with exquisite diastereoselectivity. However, a number of limitations hinder this method, primarily the strict requirement for highly electron‐deficient acceptors. Herein, we present a general Lewis acid‐driven approach to address this constraint, and have developed two broad strategies enabling the modular synthesis of complex azabicycles that were entirely unattainable using the previous method. The enhanced synthetic flexibility facilitates a streamlined asymmetric cyclization, leading to a concise total synthesis of the alkaloid (−)‐tashiromine. [ABSTRACT FROM AUTHOR]

Electron-rich heteroaromatics, such as furan, thiophene and pyrrole, as well as their benzo-condensed derivatives, are of great interest as components of natural products and as starting substances for various products including high-tech materials. Although their reactions with Brønsted and Lewis acids play important roles, in particular as the primary step of various transformations, they are often disregarded and mechanistically not understood. The present publication gives a first overview about this chemistry focusing on the parent compounds. It comprises reactions with strong Brønsted acids forming adducts that can undergo intramolecular proton and/or substituent transfer reactions, ring openings or ring transformations into other heterocycles, depending on their structure. Interactions with weak Brønsted acids usually initiate oligomerizations/polymerizations. A similar behaviour is observed in reactions of these heteroaromatics with Lewis acids. Special effects are achieved when the Lewis acids are activated through primary protonation. Deuterated Brønsted acids allow straight forward deuteration of electron-rich heteroaromatics. Mercury salts as extremely weak Lewis acids cause direct metalation in a straight forward way replacing ring H-atoms yielding organomercury heterocycles. This review will provide comprehensive information about the chemistry of adducts of such heterocycles with Brønsted and Lewis acids enabling chemists to understand the mechanisms and the potential of this field and to apply the findings in future syntheses. [ABSTRACT FROM AUTHOR]

The activation of C(sp3)−F bonds by the commercially available catalyst B(C6F5)3 is reported and applied in reactions with arenes, allylic, vinylic and acetylenic silanes, and olefins to achieve a variety of C−C bond formations (45 examples). [ABSTRACT FROM AUTHOR]

Metal triflate-catalyzed acylation of sulfonamides and direct transacylation of N-acylsulfonamides have been investigated. The acylation of sulfonamides proceeds efficiently in the presence of a catalytic amount of Cu(OTf)2 (0.001 equiv) using either carboxylic anhydrides or acyl chlorides as the acylating agents. Alternative catalysts suitable for this transformation include Al(OTf)3, Fe(OTf)3, Ga(OTf)3, In(OTf)3, and Er(OTf)3. In the presence of Cu(OTf)2 (0.2 equiv), N-acylsulfonamides undergo direct transacylation in excess acyl chlorides (10 equiv) to furnish new N-acylsulfonamides through exchange of N-acyl groups. Ga(OTf)3, Fe(OTf)3, and In(OTf)3 are similarly reactive in catalyzing such transacylation transformations. The reaction conditions are mild and operationally convenient. A variety of functional groups including halogeno, keto, nitro, cyano, ether, and carboxylic ester are tolerated, providing the corresponding monoacylated N-acylsulfonamides in good to excellent yields. [ABSTRACT FROM AUTHOR]

Isomerization of glucose to fructose is a fundamental and key intermediate process commonly included in the production of valuable chemicals from carbohydrates in biorefinery. Enhancement of fructose yield is a challenge. In this work, Sn-doped silica nanotube (Sn-SNT) was developed as a highly efficient Lewis acid catalyst for the selective isomerization of glucose to fructose. Over Sn-SNT, 69.1 % fructose yield with 78.5 % selectivity was obtained after reaction at 110 °C for 6 h. The sole presence of a large amount of Lewis acid sites in Sn-SNT without Brønsted acid site is one of the reasons for the high fructose yield and selectivity. Otherwise, high density of Si−OH groups in Sn-SNT can ensure the presence of Si−OH groups near the Sn sites, which is important for the isomerization of glucose to fructose, leading to the high fructose yield and selectivity. Furthermore, the Sn-SNT is recyclable.

Lewis acidic boron compounds are ubiquitous in chemistry due to their numerous applications, yet tuning and optimizing their properties towards different purposes is still a challenging field of research. In this work, the boron‐based Lewis acid B[OTeF3(C6F5)2]3 was synthesized by reaction of the teflate derivative HOTeF3(C6F5)2 with BCl3 or BCl3 ⋅ SMe2. This new compound presents a remarkably high thermal stability up to 300 °C, as well as one of the most sterically encumbered boron centres known in the literature. Theoretical and experimental methods revealed that B[OTeF3(C6F5)2]3 exhibits a comparable Lewis acidity to that of the well‐known B(C6F5)3. The affinity of B[OTeF3(C6F5)2]3 towards pyridine was accessed by Isothermal Titration Calorimetry (ITC) and compared to that of B(OTeF5)3 and B(C6F5)3. The ligand‐transfer reactivity of this new boron compound towards different fluorides was demonstrated by the formation of an anionic Au(III) complex and a hypervalent iodine(III) species. [ABSTRACT FROM AUTHOR]

A series of substituted ferrocenyl boron derivatives was synthesized. The oxidation of the ferrocenyl unit resulted in a significant increase of the boron‐centered Lewis acidity. The neutral and cationic Lewis acids were characterized by NMR spectroscopy, crystal structure analysis and by computational methods. The new Lewis acids were then applied in the Meinwald rearrangement of epoxides, predominantly furnishing aldehydes as the kinetic products. [ABSTRACT FROM AUTHOR]

The synthesis of cyclic polymers via zwitterionic ring expansion polymerization is limited to a few number of monomer and catalyst pairs. Herein we report the synthesis of cyclic poly(tert‐butyl glycidyl ether) through the polymerization of tert‐butyl glycidyl ether (tBGE) with B(C6F5)3 in different reaction conditions that include different solvents, monomer to initiator ratio, monomer concentration and temperature. We found that bimodal molecular weight distribution is formed in almost all reaction conditions caused by cyclization of short chains. Subsequent chain elongation leads to the formation of cycles of higher molecular weight, particularly in cyclohexane and under bulk conditions. The formation of non‐cyclic byproducts is common in all the systems investigated. Low molecular weight cyclic chains (Mn = 0.7 kDa, Ð = 1.1) of high topological purity were successfully isolated by preparative gel permeation chromatography. By using a click scavenging protocol, the non‐cyclic byproducts were eliminated from the high molecular weight fraction (Mn = 3 kDa, Ð = 1.3) generating pure cyclic chains. Mechanistic investigation using density functional theory calculations was performed on the formation of zwitterionic intermediates and the transfer reaction to the monomer, which notably affects chain growth by the attack of the glycidyl oxygen of the monomer on the growing chain. [ABSTRACT FROM AUTHOR]

Present calculations reveal that complexation with a Lewis acid such as BH3 dramatically increases the strength of hydrogen bonding between H2O, H2S, HF, HCl, and NH3 dimers. The increase in strength is attributed to the increase in electrostatic component. The interaction energies were found to increase by two to three folds (more than 50% increase in interaction energies). Detailed electronic structure analyses within the realm of quantum theory of atoms in molecules and non‐covalent interaction index confirms the strengthening of hydrogen bonding due to Lewis acid complexation. Decomposition of interaction energies using symmetry adapted perturbation theory reveals that the increase in interaction energy (more than 60%) is due to the dramatic increase in electrostatic component. [ABSTRACT FROM AUTHOR]

The wide use of boronic compounds, especially boronic acids and benzoxaboroles, in virtually all fields of chemistry is related to their specific properties. The most important of them are the ability to form cyclic esters with diols and the complexation of anions. In both cases, the equilibrium of the reaction depends mainly on the acidity of the compounds, although other factors must also be taken into account. Quantification of the acidity (pKa value) is a fundamental factor considered when designing new compounds of practical importance. The aim of the current work was to collect available values of the acidity constants of monosubstituted phenylboronic acids, critically evaluate these data, and supplement the database with data for missing compounds. Measurements were made using various methods, as a result of which a fast and reliable method for determining the pKa of boronic compounds was selected. For an extensive database of monosubstituted phenylboronic acids, their correlation with their Brønsted analogues—namely carboxylic acids—was examined. Compounds with ortho substituents do not show any correlation, which is due to the different natures of both types of acids. Nonetheless, both meta- and para-substituted compounds show excellent correlation. From a practical point of view, acidity constants are best determined from the Hammett equation. Computational approaches for determining acidity constants were also analyzed. In general, the reported calculated values are not compatible with experimental ones, providing comparable results only for selected groups of compounds. [ABSTRACT FROM AUTHOR]

Lewis acid heterogeneous catalyst, ZnAl2O4/SiO2 nanocomposite, was determined as a strong catalyst for the green and safe three-component reactions by the one-pot procedure. The effect of factors, such as the amount of catalyst, the molar ratio of reactants, reflux time and temperature on the three-component reactions were investigated. Also, the parameters of green chemistry were studied. These reactions under solvent-free conditions in the presence of ZnAl2O4/SiO2 dramatically increased the yield of the formation of dihydropyrimidinones derivatives in a very short time. The results showed that ZnAl2O4/SiO2 under solvent-free conditions greatly accelerate the three-component reactions with the advance of imine pathway and preventing the formation of unwanted side-products. Also, aromatic aldehydes with low electron density had the best outcomes. Lower reaction yield was produced by β-ketoesters with more steric hindrance. Without noticeably altering reaction time or yield, this catalyst employed six times. The technique is environmentally friendly, as shown by its low E-factor of 0.218–0.570 and high atom economy of 90.025–87.237. [ABSTRACT FROM AUTHOR]

Vapor-phase infiltration of organometallic or inorganic compounds was used to synthesize Lewis-acid sites in both amorphous SiO2 and mesoporous SBA-15. Isolated Zr and Sn sites produced in this manner exhibited similar reaction and adsorption properties as that observed for Zr-BEA and Sn-BEA zeolites. Adsorbed CD3CN showed a characteristic ν(C≡N) stretch at 2300 cm−1 which was not observed on bulk ZrO2 or siliceous materials. Zr- and Sn-modified SiO2 and SBA-15 also showed similar activities to Zr-BEA and Sn-BEA for transfer hydrogenation/etherification of 5-hydroxymethylfurfural with 2-propanol and the Diels–Alder cycloaddition/dehydration of 2,5-dimethylfuran with ethene. [ABSTRACT FROM AUTHOR]

New nanocatalyst Lewis acid type promoted MCM-41@silyl-n-propyl modified 1,4-diazabicyclo[2.2.2]octane (MCM-41@SnPr-DABCO-H) as an effective, metal-free and heterogeneous reusable nanocatalyst was synthesized and characterized by FT-IR, SEM, TEM, EDS, XRD, TGA-DTG and Brunauer–Emmett–Teller (BET) techniques. This nanocatalyst was used in the clean synthesis of various CH-tetrazoles in moderate to high yields. The CH-tetrazoles were synthesized by the one-pot reaction of triethyl orthoformate, aniline derivatives and sodium azide in the presence of catalytic amount of nanocatalyst. CH-tetrazole structures were characterized and confirmed by FT-IR, 1H and 13C NMR spectroscopy techniques. [ABSTRACT FROM AUTHOR]

Indium triflate (In(OTf)3) has proven to be a powerful and sustainable catalyst in the synthesis of modern organic compounds, enabling a variety of transformations such as functionalization, cyclization, and multicomponent reactions. To provide insight into the most recent methods and applications, this study attempts to provide a comprehensive and up‐to‐date summary of these advances in the application of indium triflate as a catalyst in organic synthesis, focusing on the last five years of literature. The application of indium triflate as opposed to alternative indium(III) catalysts in organic transformations will be the main emphasis of this review, which will cover recent developments through research articles and reviews published between 2019 and 2023. This minireview will make a significant contribution to the existing literature by consolidating recent advancements in the use of indium triflate in modern organic synthesis. [ABSTRACT FROM AUTHOR]

We have synthesized a quinone‐incorporated bistriarylamine donor‐acceptor‐donor (D–A–D) semiconductor 1 by B(C6F5)3 (BCF) catalyzed C−H/C−H cross coupling via radical ion pair intermediates. Coordination of Lewis acids BCF and Al(ORF)3 (RF=C(CF3)3) to the semiconductor 1 afforded diradical zwitterions 2 and 3 by integer electron transfer. Upon binding to Lewis acids, the LUMO energy of 1 is significantly lowered and the band gap of the semiconductor is significantly narrowed from 1.93 eV (1) to 1.01 eV (2) and 1.06 eV (3). 2 and 3 are rare near‐infrared (NIR) diradical dyes with broad absorption both centered around 1500 nm. By introducing a photo BCF generator, 2 can be generated by light‐dependent control. Furthermore, the integer electron transfer process can also be reversibly regulated via the addition of CH3CN. In addition, the temperature of 2 sharply increased and reached as high as 110 °C in 10 s upon the irradiation of near‐infrared‐II (NIR‐II) laser (1064 nm, 0.7 W cm−2), exhibiting a fast response to laser. It displays excellent photothermal stability with a photothermal (PT) conversion efficiency of 62.26 % and high‐quality PT imaging. [ABSTRACT FROM AUTHOR]

1,3-Diene architectures are not only widely present in natural products, pharmaceuticals, and functional organic materials but also serve as versatile building blocks to furnish important functionalized molecules in synthetic chemistry due to conjugated repeating C=C units. Accordingly, various strategies to access substituted 1,3-dienes in a stereoselective manner have been developed. However, chemo-, regio- and stereoselective synthesis of highly substituted 1,3-dienes still remains elusive and challenging. Readily available propargylic esters have emerged as an appealing class of synthetic intermediates for accessing functionalized 1,3-dienes, especially challenging tri- or tetrasubstituted variants, via transition-metal catalysis, including electrophilic metal and redox neutral catalysis. This review, for the first time, systematically highlights recent advances in transition-metal catalyzed synthesis of substituted 1,3-dienes from propargylic esters, discusses the mechanisms and synthetic utilities, and gives the remaining challenges and potential opportunities in this field. [ABSTRACT FROM AUTHOR]

Traditional H2O2 cleavage mediated by macroscopic electron transfer (MET) not only has low utilization of H2O2, but also sacrifices the stability of catalysts. We present a non‐redox hydroxyl‐enriched spinel (CuFe2O4) catalyst with dual Lewis acid sites to realize the homolytic cleavage of H2O2. The results of systematic experiments, in situ characterizations, and theoretical calculations confirm that tetrahedral Cu sites with optimal Lewis acidity and strong electron delocalization can synergistically elongate the O−O bonds (1.47 Å → 1.87 Å) in collaboration with adjacent bridging hydroxyl (another Lewis acid site). As a result, the free energy of H2O2 homolytic cleavage is decreased (1.28 eV → 0.98 eV). H2O2 can be efficiently split into ⋅OH induced by hydroxyl‐enriched CuFe2O4 without MET, which greatly improves the catalyst stability and the H2O2 utilization (65.2 %, nearly 2 times than traditional catalysts). The system assembled with hydroxyl‐enriched CuFe2O4 and H2O2 affords exceptional performance for organic pollutant elimination. The scale‐up experiment using a continuous flow reactor realizes long‐term stability (up to 600 mL), confirming the tremendous potential of hydroxyl‐enriched CuFe2O4 for practical applications. [ABSTRACT FROM AUTHOR]

Transforming polyolefin waste into liquid alkanes through tandem cracking‐alkylation reactions catalyzed by Lewis‐acid chlorides offers an efficient route for single‐step plastic upcycling. Lewis acids in dichloromethane establish a polar environment that stabilizes carbenium ion intermediates and catalyzes hydride transfer, enabling breaking of polyethylene C−C bonds and forming C−C bonds in alkylation. Here, we show that efficient and selective deconstruction of low‐density polyethylene (LDPE) to liquid alkanes is achieved with anhydrous aluminum chloride (AlCl3) and gallium chloride (GaCl3). Already at 60 °C, complete LDPE conversion was achieved, while maintaining the selectivity for gasoline‐range liquid alkanes over 70 %. AlCl3 showed an exceptional conversion rate of 5000 gLDPEmolcat-1h-1 ${{{\rm g}}_{{\rm L}{\rm D}{\rm P}{\rm E}}{{\rm \ }{\rm m}{\rm o}{\rm l}}_{{\rm c}{\rm a}{\rm t}}^{-1}{{\rm \ }{\rm h}}^{-1}}$ , surpassing other Lewis acid catalysts by two orders of magnitude. Through kinetic and mechanistic studies, we show that the rates of LDPE conversion do not correlate directly with the intrinsic strength of the Lewis acids or steric constraints that may limit the polymer to access the Lewis acid sites. Instead, the rates for the tandem processes of cracking and alkylation are primarily governed by the rates of initiation of carbenium ions and the subsequent intermolecular hydride transfer. Both jointly control the relative rates of cracking and alkylation, thereby determining the overall conversion and selectivity. [ABSTRACT FROM AUTHOR]

Lewis superacids (LSA) are defined by a fluoride ion affinity (FIA) that exceeds that of SbF5, and are thus characterized as hard according to the HSAB concept. Soft superacidity was defined for compounds exceeding the hydride ion affinity (HIA) of B(C6F5)3. Herein we report on the synthesis of a Lewis acid being superacidic only on the soft regime: tris(pentafluoroethyl)indane, In(C2F5)3. It is accessible in the form of its dihydrate [In(C2F5)3(OH2)2]. An improved synthesis for the gallium analogue [Ga(C2F5)3(OH2)2] is also reported. Tris(pentafluoroethyl)indane dihydrate, [In(C2F5)3(OH2)2], was fully characterized by IR and NMR spectroscopy, as well as by single crystal X‐ray diffraction. Due to their stability and convenient accessibility, the hydrates are ideal starting compounds for the chemistry of tris(pentafluoroethyl)gallium and ‐indium compounds, for example hydroxogallates and ‐indates. An attempt to determine its gas‐phase structure and that of the gallium analogue by electron diffraction demonstrates that they lose water ligands upon evaporation. The energetics of these processes were predicted by quantum‐chemical calculations as was the nature of bonding in the free Lewis acids and their mono‐ and dihydrates. Furthermore, the synthesis and structural diversity of hydroxido tris(pentafluoroethyl) gallates and one indate are presented. [ABSTRACT FROM AUTHOR]

Here we report the challenging O‐trifluoromethylation of carboxylic acids via the formation and activation of acyloxy(phenyl)trifluoromethyl‐λ3‐iodanes. The method provides an easy access to various potentially valuable and hitherto elusive trifluoromethyl carboxylic esters. A remarkably wide range of substrates with commonly encountered functional groups are compatible with this reaction, including aromatic and aliphatic carboxylic acids, as well as Food and Drug Administration (FDA) approved drugs and pharmaceutically relevant molecules. The reaction mechanism and the origins of the enhanced reactivity by zinc chloride (ZnCl2) were discussed from experimental evidence and density functional theory (DFT) calculation. [ABSTRACT FROM AUTHOR]

2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO•), a persistent nitronyl nitroxide radical, has been used for the detection and trapping of nitric oxide, as a redox mediator for batteries, for the activity estimation of antioxidants, and so on. However, there is no report on the reactivity of PTIO• in the presence of redox-inactive metal ions. In this study, it is demonstrated that the addition of scandium triflate, Sc(OTf)3 (OTf = OSO2CF3), to an acetonitrile (MeCN) solution of PTIO• resulted in an electron-transfer disproportionation to generate the corresponding cation (PTIO+) and anion (PTIO−), the latter of which is suggested to be stabilized by Sc3+ to form [(PTIO)Sc]2+. The decay of the absorption band at 361 nm due to PTIO•, monitored using a stopped-flow technique, obeyed second-order kinetics. The second-order rate constant for the disproportionation, thus determined, increased with increasing the Sc(OTf)3 concentration to reach a constant value. A drastic change in the cyclic voltammogram recorded for PTIO• in deaerated MeCN containing 0.10 M Bu4NClO4 was also observed upon addition of Sc(OTf)3, suggesting that the large positive shift of the one-electron reduction potential of PTIO• (equivalent to the one-electron oxidation potential of PTIO−) in the presence of Sc(OTf)3 may result in the disproportionation. When H2O was added to the PTIO•–Sc(OTf)3 system in deaerated MeCN, PTIO• was completely regenerated. It is suggested that the complex formation of Sc3+ with H2O may weaken the interaction between PTIO− and Sc3+, leading to electron-transfer comproportionation to regenerate PTIO•. The reversible disproportionation of PTIO• was also confirmed by electron paramagnetic resonance (EPR) spectroscopy. [ABSTRACT FROM AUTHOR]

This research focuses on studying of the process of glycolysis of polycarbonate (PC) catalyzed by zinc chloride. The degradation of polyester into monomers (bisphenol A, or BPA, and ethylene carbonate, or EC), which may then interact with one another to generate the matching ethers, was discovered to be the process. As a result, the optimal conditions for the depolymerization of PC to obtain bisphenol A and ethylene carbonate with the highest yield were therefore identified as 190 °C, a molar ratio of 11 between EG and PC, and a mass concentration of 0.4% ZnCl2. A scheme of PC glycolysis has been proposed, and a mathematical model adequately describing the experimental data has been developed. [ABSTRACT FROM AUTHOR]

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Biomass is a renewable alternative to fossil fuels and a valuable source of chemicals. In this study, a facile and efficient method was established to improve the selectivity of methyl lactate (MLA) for the homogeneous Lewis acid catalyzed chemical conversion of glucose and methanol. The effects of catalyst dosage, reaction temperature, and reaction time were systematically investigated, with an emphasis on the variation trends of MLA and other by-products. Through process optimization, the best catalyst molar ratio was 0.075 to 0.1, the reaction temperature was 170 to 180 °C, and the reaction time was 3 h. Under these conditions, the conversion of glucose in methanol exceeded 98%, and the yield of MLA was greater than 40%.

Nickel complexes with a two‐electron reduced CO2 ligand (CO22−, "carbonite") are investigated with regard to the influence alkali metal (AM) ions have as Lewis acids on the activation of the CO2 entity. For this purpose complexes with NiII(CO2)AM (AM=Li, Na, K) moieties were accessed via deprotonation of nickel‐formate compounds with (AM)N(iPr)2. It was found that not only the nature of the AM ions in vicinity to CO2 affect the activation, but also the number and the ligation of a given AM. To this end the effects of added (AM)N(R)2, THF, open and closed polyethers as well as cryptands were systematically studied. In 14 cases the products were characterized by X‐ray diffraction and correlations with the situation in solution were made. The more the AM ions get detached from the carbonite ligand, the lower is the degree of aggregation. At the same time the extent of CO2 activation is decreased as indicated by the structural and spectroscopic analysis and reactivity studies. Accompanying DFT studies showed that the coordinating AM Lewis acidic fragment withdraws only a small amount of charge from the carbonite moiety, but it also affects the internal charge equilibration between the LtBuNi and carbonite moieties. [ABSTRACT FROM AUTHOR]

The trifluoromethylsulfinylation reaction of activated arenes with trifluoromethanesulfinyl chloride (CF3SOCl) in the presence of Lewis acid was achieved under mild and solvent‐free conditions. A series of aryl trifluoromethyl sulfoxides were obtained in moderate to high yields. The protocol could be extended to the perfluoroalkylsulfinylation of activated arenes, as well as the trifluoromethylsulfinylation of indoles without additive. [ABSTRACT FROM AUTHOR]

2‐Acetonaphthones, which bear an alkenyl group tethered to its C1 carbon atom via an oxygen atom, were found to undergo an enantioselective intramolecular ortho photocycloaddition reaction. A chiral oxazaborolidine Lewis acid leads to a bathochromic absorption shift of the substrate and enables an efficient enantioface differentiation. Visible light irradiation (λ=450 nm) triggers the reaction which is tolerant of various groups at almost any position except carbon atom C8 (16 examples, 53–99 % yield, 80–97 % ee). Consecutive reactions were explored including a sensitized rearrangement to tetrahydrobiphenylenes, which occurred with full retention of configuration. Evidence was collected that the catalytic photocycloaddition occurs via triplet intermediates, and the binding mode of the acetonaphthone to the chiral Lewis acid was elucidated by DFT calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi-based MOF (Bi-HHTP) was used for the photo-driven CO 2 cycloaddition reaction and a relatively high yield was obtained. • Bi has more flexible and diverse coordination modes, which can provide abundant adsorption sites for epoxide and CO 2. • Bi-HHTP exhibits a photothermal and photocatalytic synergistic effect towards photo-driven CO 2 cycloaddition. The cycloaddition reaction between CO 2 and epoxide is an efficient way to convert CO 2 into high value-added chemicals. Therefore, it is particularly important to develop efficient catalysts that can catalyze the reaction under mild conditions. In this work, a metal–organic framework (Bi-HHTP, consisting of bismuth (Bi) as metal dots and 2,3,6,7,10,11-hexahydroxy-triphenylene (HHTP) as organic linkers) with zigzagging corrugated topology was successfully synthesized, which shows excellent catalytic activity under visible light irradiation. Various characterizations suggest that the excellent activity is derived from the following reasons: (1) the abundant exposed Bi sites provide Lewis sites for adsorption of epoxides and CO 2 ; (2) the free holes produced over Bi-HHTP under light irradiation which could oxidize epoxide, which consequently facilitateing the subsequent ring-opening reaction; and (3) the existence of synergistic photocatalytic and photothermal effect in Bi-HHTP. This study provides a new avenue of developing bismuth-based metal organic frameworks to promote the efficiency of cycloaddition of CO 2 under mild conditions. [ABSTRACT FROM AUTHOR]

Dimethyldichlorosilane has been one of the most widely used monomers in the organic silicon industry chain, which can be synthesised through the methylchlorosilanes disproportionation reaction with the interchange of functional groups. In this research, the disproportionation mechanism catalysed by ZSM-5(3 T)@MIL-53(Al) and AlCl3/ZSM-5(3 T)@MIL-53(Al) core–shell catalysts were studied by using the hybrid functional method on the level of M06-2X/Def2-TZVP. The results showed that the two catalysts possessed different catalytic effect assigning to their different acidic active structures. The surface activity of ZSM-5(3 T)@MIL-53(Al) core–shell catalyst modified by AlCl3 transformed to Lewis acid center of Al–Cl bond with better disproportionation activity than before modification. Energy, frequency vibration and IRC calculations, bond level, ELF and LOL analyses were used to verify the reaction mechanism proposed in this manuscript. [ABSTRACT FROM AUTHOR]

This document provides information on the synthesis and characterization of several compounds. The compounds were prepared using a general procedure and purified by column chromatography. The compounds were then analyzed using various techniques such as 1H NMR and 13C NMR spectroscopy. The results of these analyses are reported, including the chemical shifts of the compounds. The compounds were also analyzed using high-resolution mass spectrometry (HRMS) to determine their molecular weights. The results of the HRMS analyses are also reported. Overall, this document provides detailed information on the synthesis and characterization of these compounds, which may be useful for researchers studying similar compounds or conducting related research. The document provides information on the synthesis and characterization of various compounds. The compounds are described in terms of their chemical structures and physical properties, such as NMR spectra and mass spectrometry data. The compounds include derivatives of a pyran-2-ylmethyl group with various substituents, such as phenylthio, phenylsulfinyl, and phenylsulfonyl. The compounds were prepared using specific procedures and purified by column chromatography. The yields and physical properties of the compounds are also provided. This document provides information about the synthesis and characterization of three compounds (6b, 6c, and 6d) by Bindu Tiwari and her colleagues. The compounds were prepared using a general procedure and purified through column chromatography. The compounds were characterized using various techniques such as 1 [Extracted from the article]

The synthesis of natural products with complicated architectures often requires the use of segments with functional groups that can be structurally transformed with the desired stereogenic centers. Bicyclic -lactones have great potential as a suitable segment for natural product synthesis. However, the stereoselective construction of such functionalized bicyclic -lactones is not as straightforward as one might expect. The template-mediated Diels–Alder reaction is one of the most powerful and versatile methods for providing bicyclic -lactones with high regioselectivity and stereoselectivity. In this reaction, the diene is linked to the dienophile by a temporary tether, allowing the reaction to proceed efficiently, yielding a product that can be used for natural product synthesis. This review describes some important instances of the template-mediated Diels–Alder reaction and its application to the synthesis of biologically active compounds. [ABSTRACT FROM AUTHOR]

MgCl2·nEtOH adducts play a major role in the industrial production of polyethylenes. Their chemical dealcoholation, usually accomplished during the catalyst synthesis step, has had a pronounced impact on the microstructure of the final Ziegler–Natta pre‐catalysts and the properties of the resulting polymers. Due to the industrial and academic importance of this issue, different aluminum‐based compounds including triethylaluminum (TEAL), triisobutylaluminum (TIBA), and ethylaluminumdichloride (EADC) were used in this research in the chemical dealcoholation of a MgCl2·1.5EtOH adduct, to provide the target catalysts. According to the analytical results, the catalysts synthesized using aluminum compounds (especially TEAL and EADC) generally had a more fractured structure, a smaller particle size and a vast surface area. Aluminum precursors bind to the catalyst structure together with TiCl4, which is manifested from their higher adsorption energies obtained by DFT calculations, and the presence of Al atom in the elemental analysis. Varying the chemical structure and physical properties of the catalysts, established using Al compounds, caused significant variation in the ethylene polymerization kinetic curves, their related rate constants, and the flow characteristic of the final polymers. The overall results outstandingly affirm that by appropriate choice of the Lewis acid compound, during the chemical dealcoholation of the adduct, various Ziegler–Natta catalysts can be achieved for different polyethylene grades. [ABSTRACT FROM AUTHOR]

A method of stereodivergent intramolecular ring‐opening arylation of amine‐tethered epoxides to 3,4‐disubstituted tetrahydroquinolines has been developed. The tuneable good stereoselectivity was attained by changing the catalyst from titanocene(III) catalyst to Lewis‐acidic zinc catalyst. [ABSTRACT FROM AUTHOR]