Reaction Conditions Research Articles

Sulfonamides and sulfonate esters: Synthetic routes, proposed mechanisms, and crystallographic characterizations

The sulfonamide and sulfonate moieties are key structural features in many pharmaceuticals, agrochemicals, and materials and have proven useful as synthetic precursors. In this review, synthetic routes for sulfonamides and sulfonate esters were examined to gain insight into the mechanism behind the sulfonylation of amines and alcohols, which remains largely unknown and highly dependent on the reaction conditions used. Furthermore, the review delves into crystallographic characterizations of previously reported sulfonamide and sulfonate ester compounds, unraveling trends associated with crucial steric and electronic factors that influence their crystallization. This exploration not only enhances our understanding of the structural nuances of these compounds, but also paves the way for informed design strategies in synthetic and medicinal chemistry. In essence, this review endeavors to provide a holistic perspective on sulfonamides and sulfonate esters, bridging the realms of synthesis, mechanism elucidation, and structural characterization.

Hypervalent iodine-mediated cyclization of bishomoallylamides to prolinols

A change in mechanism was observed in the hypervalent iodine-mediated cyclization of N-alkenylamides when the carbon chain between the alkene and the amide increased from two to three atoms. In the latter case, cyclization at the amide nitrogen to form the pyrrolidine ring was favored over cyclization at the amide oxygen. A DFT study was undertaken to rationalize the change in mechanism of this cyclization process. In addition, reaction conditions were developed, and the scope of this cyclization studied.

Efficient Hydroboration of Ketones and Imines Using Amidophosphine‐borane under Catalyst‐Free Conditions

We report here the use of amidophosphine borane {(BH₃)₂(PPh)₂N(CH₂)C₆H₅} as a competent reducing agent for the hydroboration of ketones and imines, yielding the corresponding secondary alcohols and secondary amines under mild and catalyst‐free reaction conditions. Solid amidophosphine boranes, which are easy to synthesize, and easy to handle demonstrated excellent reactivity and functional group tolerance toward a wide variety of ketones and imines, including aromatic, heteroaromatic, and aliphatic derivatives with electron‐withdrawing and electron‐donating substitutions, thus showing excellent chemoselectivity.

Oxidative Coupling of Methane: A Review Study on the Catalytic Performance

Extensive data on the characteristics and performance of the catalysts synthesized and tested for methane oxidative coupling (OCM) is available in thousands of reports published during the last four decades. Revisiting and analyzing the general trends recognizable in those data could improve the current understanding of the catalyst functionality under different reaction conditions. This is instrumental in determining the direction of future research aiming for more efficient OCM catalysts and reactors. These are the subjects of the comprehensive analysis reported in this paper, which covers the main aspects associated with the analysis of the OCM catalytic performance, including the catalyst characteristics, reaction mechanism, and reactor operation. Special attention was devoted to analyzing these aspects in the framework of thermal-reaction engineering and, accordingly, critically reviewing the reported catalytic performances in the literature.

Synthesis and in vitro Biological Evaluation of a Series of 5-Benzylidene Derivatives of Rhodanine-Sulfonylurea Hybrid as a Novel Class of α-Glucosidase Inhibitors

A novel rhodanine-sulfonylurea hybrid (C) has been prepared based on the isocyanate-amine reaction conditions in the first step and its 5-benzylidene analogues (C1-C13) were synthesized using Knoevenagel reaction conditions as the subsequent step. The physical and spectral characterization of all the synthesized compounds (C-C13) was performed using FT-IR, 1H NMR and HR-ESI-MS spectral methods. All compounds were subjected to in vitro α-glucosidase enzyme inhibitory properties at 100 µM concentration. The results were compared with a standard drug, voglibose, also tested at the similar concentrations. The bioassay results revealed that the intermediate compound C was more potent with a percentage inhibitory activity of 64.86%, which is relatively better than the series of 5-benzylidene analogues (C1-C13) synthesized from the intermediate C. This clearly displayed that substitution at position-5 on the rhodanine ring of intermediate C is not a favourable substitution to enhance the bioactivity; however, one of the derivative compounds, C12, has exhibited potency of 58.32%, which is close to the compound C. It is significant that both the intermediate C and compound C12 displayed better potency compared to the standard voglibose, with percentage inhibition recorded at 37.75%. The additive or synergistic potential of the bioactive pharmacophore tosylurea, which was earlier established, tolerated the rhodanine ring substitution towards retaining the α-glucosidase inhibitory properties.

Decoding the Promotional Effect of Iron in Bimetallic Pt-Fe-nanoparticles on the Low Temperature Reverse Water-Gas Shift Reaction.

The reverse water-gas shift (RWGS) reaction is a key technology of the chemical industry, central to the emerging circular carbon economy. Pt-based catalysts have previously been shown to effectively promote RWGS, especially when modified by promoter elements. However, their active states are still poorly understood. Here, we show that the intimate incorporation of an iron promoter into metal-oxide-supported Pt-based nanoparticles can increase their activity and selectivity for the low temperature reverse water-gas shift (LT-RWGS) substantially and drastically outperform unpromoted Pt-based materials. Specifically, the study explores the promotional effect of iron in Pt-Fe bimetallic systems supported on silica (PtxFey@SiO2) prepared by surface organometallic chemistry (SOMC). The most active catalyst (Pt1Fe1@SiO2) shows high selectivity (>99% CO) toward CO at a formation rate of 0.192 molCO h-1 gcat-1, which is significantly higher than that of monometallic Pt@SiO2 (96% sel. and 0.022 molCO h-1 gcat-1). In-situ diffuse reflectance FT-IR spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS) indicate a dynamic process at the catalyst surface under the reaction conditions, revealing distinct reaction pathways for the monometallic Pt@SiO2 and bimetallic PtxFey@SiO2 systems.

Synergistically enhanced heterogeneous activation of dissolved oxygen for aqueous carbamazepine degradation over S(III) coupled with siderite

The wide occurrence of emerging contaminants (ECs) was drawing more attention due to the potential hazard and threat on human and environment. Carbamazepine (CBZ) is a widely prescribed medication that has garnered considerable research interest with the exposures exceeding the environmental carrying capacity. We have established the innovative heterogeneous advanced oxidation process (AOPs) based on the activated dissolved oxygen (DO) coupled with S(III) and natural iron ore (siderite). In S(III)/O2/siderite system, we investigated the degradation efficiency, reactive species generation mechanism, and degradation pathway of CBZ. CBZ degradation and mineralization rate were 90% above and ∼15% with the reaction time of 40 min. The degradation of CBZ conformed to a pseudo-first-order kinetic model, with an activation energy determination of 76.36 kJ/mol. The optimal initial solution pH was the weak acid condition (pH = 4–6) for CBZ degradation. Moreover, the inhibition effects of coexisting substance including Cl−, HCO3−, and natural organic matter (NOM) on CBZ removal were observed, while the coexisted SO42− exhibited no significant influence. In addition, the reactive species generated in S(III)/O2/siderite system were predominantly identified as sulfate radical (SO4∙-) and hydroxyl radical (∙OH). The crucial intermediate complexes, Fe(III)S(IV)O3(+) and Fe(II)HS(IV)O3(+), was proposed to form in the initial stages of the reaction, which upon decomposition, yielded SO4∙- along with other reactive species. The degradation pathway of CBZ primarily involved deamination, oxidative ring-opening, hydroxylation, decarboxylation, and ketone degradation processes. This work provides the effective approach for the CBZ degradation with the mild reaction conditions and the sustainable technology for ECs treatment and control.

Degradation of organic dyes by Peroxymonosulfate activated with Zn/Co-ZIF

In this study, we successfully synthesized a bimetallic metal-organic framework material Zn/Co-ZIF to start Peroxymonosulfate (PMS) for organic dye degradation in the water body. Material characterization was evaluated by advanced methods, such as XRD, FT-IR, SEM, EDX, and BET. The influence of different factors on methylene blue (MB) decomposition rate was investigated. The results show that Zn/Co-ZIF has a porous structure, a high specific surface area and decomposes 98.22% MB (20 mg/L) in 4 minutes under reaction conditions of 40 mg/L catalyst, 0.814mM PMS, pH = 7. The decomposition efficiency of dyes increases in the order CR (79.85%) <RhB (90.81 %) < DB71 (96.07%) < MO (97.63%) < MB (98.22%). The main ROS for the degradation MB in this study were SO4—-, O2—- and 1O2. This shows that Zn/Co-ZIF materials are potential heterogeneous catalysts to activate PMS to decompose organic pollutants in water.

Practical Copper‐Catalyzed Double N‐Arylation of Cyclic Diaryliodoniums: Synthesis of 5H‐Dibenzo[d, f][1,3]Diazepine, and Benzo[c]Cinnoline Derivatives

ABSTRACTAn efficient access to novel families of 7‐membered dibenzodiazepines and 6‐membered benzo[c]cinnoline derivatives has been elaborated. The synthetic strategy is based on a copper‐catalyzed double N‐arylation of cyclic diaryliodoniums with imidamides and 4‐substituted 1, 2, 4‐triazoline‐3, 5‐diones (TADs) respectively under ambient reaction conditions. A mechanistic rationale for the double N‐arylation is discussed.

L‐Cysteine‐Catalysed Hydration of Activated Alkynes

Hydration reactions consist of the introduction of a molecule of water into a chemical compound and are particularly useful to transform alkynes into carbonyls, which are strategic intermediates in the synthesis of a plethora of compounds. Herein we demonstrate that L‐cysteine can catalyse the hydration of activated alkynes in a very effective and fully regioselective manner to access important building blocks in synthetic chemistry such as β‐ketosulfones, amides and esters, in aqueous media. The mild reaction conditions facilitated the integration with enzyme catalysis to access chiral β‐hydroxy sulfones from the corresponding alkynes in a one‐pot cascade process in good yields and excellent enantiomeric ratios. These findings pave the way towards establishing a general method for metal‐free, cost‐effective, and more sustainable alkyne hydration processes.

An Efficient Multi‐Component Double Friedel‐Crafts Alkylation of Isatin: Access to Unsymmetrical and Symmetrical 3, 3‐Diaryl oxindoles

AbstractAcetic acid‐mediated three‐component double Friedel–Crafts alkylation reaction for the synthesis of α, α‐diaryl oxindole derivatives is demonstrated. The reaction is successful with various isatin, indole, and N, N‐disubstituted aniline derivatives. The efficiency of the reaction is further enhanced by a four‐component reaction of isatin, electrophiles and acetic anhydride for the synthesis of N‐acylated 3,3‐diaryl oxindole derivatives facilitated by dual activation of C3 and N1 acetylation in a single‐step. Various unsymmetrical and symmetrical 3,3‐diaryl oxindoles were prepared in single‐step MCR reaction under easy to operate reaction conditions.

L-Cysteine-Catalysed Hydration of Activated Alkynes.

Hydration reactions consist of the introduction of a molecule of water into a chemical compound and are particularly useful to transform alkynes into carbonyls, which are strategic intermediates in the synthesis of a plethora of compounds. Herein we demonstrate that L-cysteine can catalyse the hydration of activated alkynes in a very effective and fully regioselective manner to access important building blocks in synthetic chemistry such as β-ketosulfones, amides and esters, in aqueous media. The mild reaction conditions facilitated the integration with enzyme catalysis to access chiral β-hydroxy sulfones from the corresponding alkynes in a one-pot cascade process in good yields and excellent enantiomeric ratios. These findings pave the way towards establishing a general method for metal-free, cost-effective, and more sustainable alkyne hydration processes.

"[18F]Trifluoroiodomethane- Enabling Photoredox-mediated Radical [18F]Trifluoromethylation for Positron Emission Tomography.

The development of new tracers for positron emission tomography (PET) is highly dependent on the available synthetic tools for their radiosynthesis. Herein, we present theradiosynthesis and application of [18F]trifluoroiodomethane - the first reagent for broad scope radical [18F]trifluoromethylation chemistry in high molar activity. CF218FI can be prepared from [18F]fluoroform with 67±5% AY and >99% RCP. Its synthetic utility is demonstrated by the radiosynthesis of previously unprecedented 18F-labeled a-trifluoromethyl ketones and trifluoromethyl sulfides, important motifs that are present in a range of bioactive compounds. Both protocols are Ru- and photo-mediated and proceed under mild reaction conditions. They show good functional group tolerance evidenced by the respective reaction scopes and make use of easily obtainable starting materials. The products can be isolated in 8.3-11.1 GBq/µmol (starting from ca. 5GBq [18F]fluoride). The applicability to PET tracer synthesis is shown by the radiolabeling of bioactive compounds, such as derivatives of probenecid and febuxostat. In a broader context, this work opens the door to the utilization of radical [18F]trifluoromethylation chemistry for the radiolabeling of PET tracers in high molar activity.

Yeast protein‐derived γ‐glutamyl peptides prepared by transpeptidation reaction exhibit a pronounced taste‐enhancing effect

AbstractA high‐salt diet can induce hypertension, so salt reduction can prevent hypertension. γ‐Glutamyl peptides (GGPs) have obvious taste‐enhancing effects, while their contents in natural foods are relatively low. Yeast protein rich in Glu/Gln is a good precursor for the preparation of GGPs. In this study, yeast protein‐derived GGPs were prepared through hydrolysis and transpeptidation reactions, followed by sensory evaluation and E‐tongue analysis. Peptide sequences were identified by LC−MS/MS and screened for molecular docking. The optimal reaction conditions were hydrolysis for 4 h, enzyme concentration of 16 U/g, and transpeptidation for 4 h. GGPs could increase salt and umami intensity by 60.78% and 40.93% based on sensory evaluation, 22.52%, and 16.40% according to E‐tongue analysis. Fifteen γ‐glutamyl peptides with different peptide lengths were selected for molecular docking. Molecular docking confirmed their binding to calcium‐sensing receptors (CaSr) through hydrogen bonds and hydrophobic interaction, while interaction between CaSR receptor and γ‐glutamyl di‐, tri‐, and oligo‐peptides varied in binding energy. The stimulation received by CaSR lasted a longer time and varied in intensity. It was further proved that the flavor of mixed peptides has a layered sense and can give people a rich taste experience. Overall, yeast protein‐derived GGPs can enhance salt and umami taste, which can reduce salt usage without compromising taste.

Crystal structures of the (η2:η2-cycloocta-1,5-diene)(η6-toluene)iridium(I) cation and μ-chlorido-iridium(III) complexes of 2-(phosphinito)- and 2-(phosphinomethyl)anthraquinone ligands

When reacted in dry, degassed toluene, [Ir(COD)Cl]2 (COD = cycloocta-1,5-diene) and 2 equivalents of 2-(di-tert-butylphosphinito)anthraquinone (tBuPOAQH) were found to form a unique tri-iridium compound consisting of one monoanionic dinuclear tri-μ-chlorido complex bearing one bidentate tBuPOAQ ligand per iridium, which was charge-balanced by an outer sphere [Ir(toluene)(COD)]+ ion, the structure of which has not previously been reported. This product, which is a toluene solvate, namely, (η2:η2-cycloocta-1,5-diene)(η6-toluene)iridium(I) tri-μ-chlorido-bis({3-[(di-tert-butylphosphanyl)oxy]-9,10-dioxoanthracen-2-yl}hydridoiridium(III)) toluene monosolvate, [Ir(C7H8)(C8H12)][Ir2H2(C22H24O3P)2Cl3]·C7H8 or [Ir(toluene)(COD)][Ir(κ-P,C-tBuPOAQ)(H)]2(μ-Cl)3]·toluene, formed as small orange platelets at room temperature, crystallizing in the triclinic space group P\overline{1}. The cation and anion are linked via weak C—H...O interactions. The stronger intermolecular attractions are likely the offset parallel π–π interactions, which occur between the toluene ligands of pairs of inverted cations and between pairs of inverted anthraquinone moieties, the latter of which are capped by toluene solvate molecules, making for π-stacks of four molecules each. The related ligand, 2-(di-tert-butylphosphinomethyl)-anthraquinone (tBuPCAQH), did not form crystals suitable for X-ray diffraction under analogous reaction conditions. However, when the reaction was conducted in chloroform, yellow needles readily formed following addition of 1 atm of carbon monoxide. Diffraction studies revealed a neutral, dinuclear, di-μ-chlorido complex, di-μ-chlorido-bis(carbonyl{3-[(di-tert-butylphosphanyl)oxy]-9,10-dioxoanthracen-2-yl}hydridoiridium(I)), [Ir2H2(C23H26O2P)2Cl2(CO)2] or [Ir(κ-P,C-tBuPCAQ)(H)(CO)(μ-Cl)]2, Ir2C48H54Cl2O6P2, again crystallizing in space group P\overline{1}. Offset parallel π–π interactions between anthraquinone groups of adjacent molecules link the molecules in one dimension.

Diimide-Mediated Hydrogenation of Nitrile Butadiene Rubber

The hydrogenation of nitrile butadiene rubber (NBR) has shown great potential for improving its physical, thermal, mechanical, and chemical stability. Hydrogenation process of NBR in this work involved the utilization of diimide produced from the interaction between hydrazine hydrate (N2H4) and hydrogen peroxide (H2O2), with the addition of boric acid as a promoter. Attenuated total reflectance Fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) were used to evaluate the degree of hydrogenation, glass transition, thermal stability, and rubber crystallinity, respectively. The highest hydrogenation degree was 99%, which resulted in a 57% gel content. Upon hydrogenation, both the glass transition temperature (Tg) and decomposition temperature (Td) increased. The hydrogenated rubber samples generally showed an amorphous state, except for the 99% hydrogenated sample, which displayed a semi-crystalline state. However, using diimide for direct hydrogenation yields a side reaction from the free radicals in the system, which leads to gel formation. Optimization was accomplished by employing the response surface methodology (RSM), which entailed manipulating parameters such as the total solid content (TSC) of NBR, reaction time, and the mole ratio of H2O2 to N2H4, to reduce the percentage of gel content. The RSM analysis identified the optimum reaction conditions as a 1:1 mole ratio of H2O2: N2H4 and 25% TSC, with a reaction time of 8 h, which yielded 32% gel content percentage, where a mole ratio of H2O2 to N2H4 and reaction time indicated a synergistic effect, whereas TSC denoted an antagonistic effect.

Tetrabutylammonium Hydrogen Sulfate (TBAHS) Catalyzed Microwave-Assisted Synthesis of 3,4,5,6,7,9-Hexahydro-1H-xanthene-1,8-(2H)-dione Derivatives and its Biological Study

In this study, a facile and eco-friendly synthesis of novel 3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione derivatives using tetrabutylammonium hydrogen sulfate (TBAHS) as a catalyst in the microwave reactor is presented. The reaction involved the condensation of aromatic aldehydes with 1,3-cyclohexanedione in ethanol as solvent, offering significant advantages in terms of reaction rate, yield and purity. The use of TBAHS as catalyst in conjunction with microwave irradiation facilitated the formation of the target xanthene derivatives in remarkably short reaction times. Moreover, Monowave 50 microwave reactor provided precise control over reaction parameters, enabling rapid optimization of reaction conditions. Further these synthesized compounds were systematically evaluated for their antibacterial, antituberculosis and antioxidant activities.

Synthesis and spectroscopic studies of triazole-based macroheterocycles containing eudesmane-type sesquiterpenoid moieties

Chiral recognition is one of the most important and fascinating areas in supramolecular chemistry. Chiral macrocycles, especially chiral macrocyclic hosts, having stable structures, adjustable internal cavities to encapsulate and complexation have been developed during the last decade. Attention has been paid on the synthesis of covalently linked of rigid units on the side chain of macrocycles with active binding motifs. In this study, new synthetic protocols has been developed for preparation of optically active triazole-based macrocyclic compounds in which eudesmane-type sesquiterpene lactones act as pendent moieties by the implementation of the copper(I)-catalyzed azid-alkyne cycloaddition strategies. The described protocols provided mild reaction conditions, high yields and high atom- and step-economy. New macrocycles with hanging dihydroisoalantolactone units, different combinations of heteroatoms, and ring sizes in the range of 16–36 atoms were characterized by NMR and UV–vis spectroscopy and mass spectrometry analysis. The molecular structures and intermolecular interactions of two new macrocyclic compounds were elucidated using single-crystal X-ray crystallography. Upon addition of Mg(II) or Zn(II) cations to these novel ligands, using titration experiments we observed the formation of 1:1 (16:Mg2+) complexes and 1:1 to 2:1 (16:Zn2+) complexes, respectively, according to stoichiometry. The result suggests that dihydriisoalantolactone and triazole units within the molecules formed complexes with Mg (II) and Zn (II) ions in solution.

Flux-Screened Copper/Electric Dual-Catalyzed Chemo- and Enantioselective Ullmann-Type C-C Coupling Reactions.

This study introduces an innovative copper/electric dual-catalyzed approach to Ullmann coupling reactions. Our research delineates a series of chemoselective cross-couplings among various halogenated aromatics and enantioselective couplings involving halogenated aryl aldehydes. We employed a flux screening technique to refine the reaction parameters, which is rarely reported in the field of electrochemical synthesis. This advancement accelerates the determination of optimal reaction conditions and affords some inspiration for developing sustainable and ecofriendly chemical synthesis.

Advancing the Coupling of III–V Quantum Dots to Photonic Structures to Shape Their Emission Diagram

AbstractThe development of optoelectronic devices based on III–V semiconductor colloidal quantum dots (CQDs) is highly sought after due to their reduced toxicity. While devices based on conventional CQDs (II–VI semiconductors, halide perovskites) have achieved impressive technological leaps since their discovery, the most mature of these compounds contain toxic heavy metal elements (Cd, Hg, or Pb), which are highly undesirable for safe industrial scale applications. The strong covalent bonds of III–V compounds like InP, InAs, or InSb prevent the release of their toxic atoms, making them safer. However, these same bonds create severe material constraints. Namely, their harsher reaction conditions and increased sensitivity to oxidation have kept most of the research focused on material development. Meanwhile, their integration into devices and their coupling to photonic structures lag behind. Here, the integration of InAs/ZnSe core‐shell CQDs is advanced. First, the material parameters necessary to design plasmonic gratings coupled to the CQDs are elucidated and those gratings are fabricated. Angle‐resolved spectroscopy shows that the plasmon modes successfully couple to the CQD layer's emission leading to a tunable directivity with a 15° linewidth. A 3‐fold increase of the PL signal is achieved at normal incidence, thus advancing toward the goal of efficient outcoupling in LEDs.