Aliphatic Halides Research Articles

A low-coordinate platinum(0)-germylene for E–H bond activation and catalytic hydrodehalogenation

Pairing transition metals and heavier tetrylenes (Si, Ge, Sn, Pb) holds great potential for cooperative bond activation and catalysis. In this work, we investigate the reactivity of a low-coordinate Pt(0)/Ge(II) system that emerges from the reaction between the monoligated platinum(0) precursor [(PMe2ArDipp2)Pt(olefin)] with germylene dimer [ArDipp2GeCl]2 (where ArDipp2 = C6H3−2,6-(C6H3−2,6-iPr2)2). The resulting complex reveals ability for cooperative bond activation. Stoichiometric reactions with dihydrogen, water, methanol, ammonia and alkynes unveil the formation of Pt(II)-germyl compounds, characterized by distinct isomeric forms, whose flexibility derives from the particularly low-coordination. We explore its catalytic potential in the hydrodehalogenation of aliphatic, aromatic and main-group halides under dihydrogen atmosphere using both thermal and photochemical conditions, demonstrating promising conversions even for more challenging alkyl chlorides.

Dialkylation of Alkenes with Aliphatic Alcohols and Alkyl Halides by Dual Nickel and Photoredox Catalysis

Dialkylation of Alkenes with Aliphatic Alcohols and Alkyl Halides by Dual Nickel and Photoredox Catalysis

Secondary Metabolite Profiling of the Endophytic Fungus Trichoderma longibrachiatum L2D2 Isolated from Anaphalis contorta

In the last few decades, research on endophytic fungi has been increasing due to its applications in agriculture, medicine, and the pharmaceutical industry. Many studies indicate that fungal endophytes produce various types of bioactive compounds. In this study, the endophytic fungus Trichoderma longibrachiatum L2D2 was isolated from the leaf of the medicinal plant Anaphalis contorta and secondary metabolites were collected. The crude extract was analyzed for the presence of seven phytochemicals, and it was observed that alkaloids, flavonoids, phenolics, steroids, tannins, and terpenoids were produced. It was also found that the endophyte extract had a total flavonoid content of 126.07 (µg of quercetin equivalent/mg) and a total phenolic content of 43.97 (µg of gallic acid equivalent/mg). The Gas Chromatography–Mass Spectrometry (GC-MS) analysis reveals the presence of the major compound Dithiooxamide, which has a retention time (RT) of 50.030%, and the Liquid Chromatography–Mass Spectrometry (LC-MS) study shows the most abundant compounds as Hexanal (RT of 3.687 min) in positive ionization and Rosamultin (RT of 24.387 min) in negative ionization. Fourier-Transform Infrared (FTIR) Spectroscopy analysis also shows the presence of alcohol, aldehyde, aliphatic ether, aliphatic primary amine, alkene, alkyl halide, amine, aromatic amine, aromatic compound, carboxylic acid, ketone, phenol, and sulfoxide as functional groups. Further studies, like the purification of bioactive compounds and their biological activities, will reveal the applicability of T. longibrachiatum L2D2 in industries.

Exploring the hidden treasures of Nitella hyalina: a comprehensive study on its biological compounds, nutritional profile, and unveiling its antimicrobial, antioxidative, and hypoglycemic properties.

Macroalgae has the potential to be a precious resource in food, pharmaceutical, and nutraceutical industries. Therefore, the present study was carried out to identify and quantify the phyco-chemicals and to assess the nutritional profile, antimicrobial, antioxidant, and anti-diabetic properties of Nitella hyalina extracts. Nutritional composition revealed0.05 ± 2.40% ash content, followed by crude protein (24.66 ± 0.95%), crude fat (17.66 ± 1.42%), crude fiber (2.17 ± 0.91%), moisture content (15.46 ± 0.48%) and calculated energy value (173.50 ± 2.90 Kcal/100g). 23 compounds were identified through GC-MS analysis in ethyl acetate extract, with primary compounds being Palmitic acid, methyl ester, (Z)-9-Hexadecenoic acid, methyl ester, and Methyl tetra decanoate. Whereas 15 compounds were identified in n-butanol extract, with the major compounds being Tetra decanoic acid, 9-hexadecanoic acid, Methyl pentopyranoside, and undecane. FT-IR spectroscopy confirmed the presence of alcoholic phenol, saturated aliphatic compounds, lipids, carboxylic acid, carbonyl, aromatic components, amine, alkyl halides, alkene, and halogen compounds. Moreover, n-butanol contains 1.663 ± 0.768mg GAE/g, of total phenolic contents (TPC,) and 2.050 ± 0.143 QE/g of total flavonoid contents (TFC), followed by ethyl acetate extract, i.e. 1.043 ± 0.961mg GAE/g and 1.730 ± 0.311mg QE/g respectively. Anti-radical scavenging effect in a range of 34.55-46.35% and 35.39-41.79% was measured for n-butanol and ethyl acetate extracts, respectively. Antimicrobial results declared that n-butanol extract had the highest growth inhibitory effect, followed by ethyl acetate extract. Pseudomonas aeruginosa was reported to be the most susceptible strain, followed by Staphylococcus aureus and Escherichia coli, while Candida albicans showed the least inhibition at all concentrations. In-vivo hypoglycemic study revealed that both extracts exhibited dose-dependent activity. Significant hypoglycemic activity was observed at a dose of 300mg/kg- 1 after 6h i.e. 241.50 ± 2.88, followed by doses of 200 and 100mg/kg- 1 (245.17 ± 3.43 and 250.67 ± 7.45, respectively) for n-butanol extract. In conclusion, the macroalgae demonstrated potency concerning antioxidant, antimicrobial, and hypoglycemic properties.

Frustrated Lewis Pair‐Catalyzed Hydroboration of Nitriles: FLP Versus Borenium Catalysis

AbstractA frustrated Lewis pair‐catalyzed hydroboration of aromatic and aliphatic nitriles was developed. The catalyst provides the primary amines in high yields of 77–99% with catalyst loading as low as 2 mol%. The reaction displays high functional group tolerance towards esters, amides, nitro groups and aliphatic halides. The addition of the diborylated amines to ethyl 3‐phenylpropiolate proceeds with Z‐selectivity with d.r. of >99:1 in 77–90% yield over two steps. The reaction mechanism was investigated by control and computational experiments.magnified image

Renewable Reagent for Nucleophilic Fluorination.

Herein, we report a study on the reactivity of three 1,3-diarylimidazolium-based fluoride reagents, with a general formula of [IPrH][F(HF)n] (n = 0, 1, or 2), that tackle the challenges of limited solubility, hygroscopicity, instability, and laborious preparation procedures of nucleophilic fluoride reagents. Fluorination of 4-tert-butylbenzyl bromide reveals that trifluoride [IPrH][F(HF)2] is the most selective reagent. Microwave-assisted activation coupled with the addition of sterically hindered amine DIPEA or alkali metal fluorides increases the rate of fluorination with [IPrH][F(HF)2], making it an excellent reagent for the fluorination of various organic substrates. The scope of substrates includes benzyl bromides, iodides, chlorides, aliphatic halides, tosylates, mesylates, α-haloketones, a silyl chloride, acyl and sulfuryl chlorides, and a nitroarene. The exceptional stability of the air-stable and nonhygroscopic [IPrH][F(HF)2] reagent is illustrated by its convenient synthesis and detailed experimental regeneration protocol using hydrofluoric acid without organic solvents.

Comparing Halogen Atom Abstraction Kinetics for Mn(I), Fe(I), Co(I), and Ni(I) Complexes by Combining Electroanalytical and Statistical Modeling

AbstractFirst‐row transition metal complexes have garnered attention due to their ability to activate aliphatic halides for catalytic cross‐coupling reactions. However, mechanistic investigation of these systems is challenging as a consequence of difficulties associated with preparing the relevant metal complexes and the resultant poor stability of such intermediates for subsequent analytical interrogation. In this context, we have developed a platform to rapidly measure kinetic data using electroanalytical methods, which facilitates a wide range of physical organic studies. As a result, we have investigated and compared the reaction of benzyllic halides with electrogenerated MnI(PyBox)Cl, FeI(Pyrox)OTf, CoI(Pyrox)Br, CoI(PyBox)Br, NiI(Phox)Br complexes. The experimental results support a unified inner‐sphere halogen atom abstraction mechanism for these different complexes while also providing the ability to directly compare through multivariate linear regression analyses the subtle differences imparted by metal/ligand combinations. The information gleaned by this study has implications why certain metal complexes are matched to oxidative addition processes relevant in catalytic processes.

Understanding biochemical defense and phytoremediation potential of Leucas aspera in crude oil polluted soil.

The phytoremediation potential and enzymatic defense of a medicinal herb Leucas aspera was studied in the crude oil contaminated soil. The productivity, antioxidants, and phytochemical and functional group profiles of the plant species in stress conditions were investigated. Besides, changes in enzymes, beneficial bacterial population, and physico-chemical and total oil and grease (TOG) profiles in the contaminated soil were also studied. The results showed improvement in physico-chemical conditions, increase in beneficial bacterial population (4.1-5.4 folds), and decrease in TOG (31.3%) level of the contaminated soil by end of the experimental trials. The L. aspera treated contaminated soil showed enhancement in dehydrogenase (32.3%), urease (102.8%), alkaline phosphatase (174.4%), catalase (68.5%), amylase (76.16%), and cellulase (23.6%) activities by end of the experimental trials. Furthermore, there were significant variations in leaf area index, chlorophyll, and biomass contents of the experimental plant as against the initial level and control. Besides, the significant reduction in IC50 values (24-27.4%) of L. aspera samples grown in contaminated soil confirms the strong antioxidant enzymatic defense of the plant species against the crude oil associated abiotic stress. The Fourier-transform infrared (FT-IR) analysis confirmed the uptake and metabolism of aliphatic hydrocarbons, aldehydes, alkyl halides, and nitro compounds by the experimental plant from the contaminated soil.

Selective Fluoromethyl Couplings of Alkynes via Nickel Catalysis

AbstractWe describe here a Ni‐catalyzed intermolecular carbo‐fluoromethylation of alkynes with aliphatic halides and fluoromethyl halides (BrCF2H and ICH2F) in the presence of zinc, enabling the facile and selective access to a diverse range of biologically valuable CF2H/CH2F‐incorporated alkenes with excellent regio‐ and stereoselectivity. Notably, merging intramolecular radical cyclization with fluoromethyl coupling enables the expedient constructions of CF2H/CH2F‐incorporated lactones and lactams with high efficiency and selectivity. Mechanistic studies disclose that this catalytic protocol proceeds via a radical addition to an alkyne followed by selective coupling with the fluoromethyl unit.

Selective Fluoromethyl Couplings of Alkynes via Nickel Catalysis

We describe here a Ni-catalyzed intermolecular carbo-fluoromethylation of alkynes with aliphatic halides and fluoromethyl halides (BrCF2 H and ICH2 F) in the presence of zinc, enabling the facile and selective access to a diverse range of biologically valuable CF2 H/CH2 F-incorporated alkenes with excellent regio- and stereoselectivity. Notably, merging intramolecular radical cyclization with fluoromethyl coupling enables the expedient constructions of CF2 H/CH2 F-incorporated lactones and lactams with high efficiency and selectivity. Mechanistic studies disclose that this catalytic protocol proceeds via a radical addition to an alkyne followed by selective coupling with the fluoromethyl unit.

Antimicrobial Properties of Ocimum Species: An In Vitro Study.

This study aimed to determine the antimicrobial activity of ethanol-extracts obtained from Ocimum gratissimum L. (clove or African basil, Lamiaceae) and O. santum L. (holy basil) against some microorganisms present in oral cavity related to either medical or dental disease. Antimicrobial properties of both ethanol-extracts of Ocimum species against Streptococcus mutans KPSK2, S. pyogenes ATCC 19615, Staphylococcus aureus ATCC 16794, and Candida albicans ATCC 10231 were primarily determined by agar disk diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal or fungicidal concentration (MBC or MFC) of these herbal extracts were further determined by broth micro-dilution method. Ethanol-extracts of O. sanctum L. and O. gratissimum L. inhibited the growth of all tested microorganisms in various degrees ranging from the strongest antimicrobial activity of O. sanctum against S. pyogenes [MIC at 0.19% (w/v); MBC at 0.78% (w/v)] to the least inhibitory activity of O. gratissimum against C. albicans [MIC at 12.5% (w/v); undetectable MFC]. The ethanol-extract of O. sanctum showed stronger antimicrobial property against the tested bacteria and fungus than O. gratissimum. The ethanol-extracts of both Ocimum species showed stronger antibacterial than antifungal activity. However, the ethanol-extract of O. gratissimum even at a high concentration of 50% (w/v) was unable to eliminate the tested fungus. Ethanol-extracts of Ocimum species contain effective antibacterial and antifungal properties that may be beneficial for further development of antimicrobial agents in medical and dental fields.

Atom Transfer Radical Polymerization-Inspired Room Temperature (sp3)C-N Coupling.

A simple nonphotochemical procedure is reported for Cu(I)-catalyzed C-N coupling of aliphatic halides with amines and amides. The process is loosely based on the Goldberg reaction but takes place readily at room temperature. It uses Cu(I)Br, a commonly used and inexpensive atom transfer radical polymerization precatalyst, along with the cheap ligand N,N,N',N″,N″-pentamethyldiethylenetriamine, to activate the R-X bond of the substrate via inner-sphere electron transfer. The procedure brings about productive C-N bond formation between a range of alkyl halide substrates with heterocyclic aromatic amines and amides. The mechanism of the coupling step, which was elucidated through application of computational methods, proceeds via a unique Cu(I) → Cu(II) → Cu(III) → Cu(I) catalytic cycle, involving (a) inner-sphere electron transfer from Cu(I) to the alkyl halide to generate the alkyl radical; (b) successive coordination of the N-nucleophile and the radical to Cu(II); and finally reductive elimination. In the absence of a nucleophile, debrominative homocoupling of the alkyl halide occurs. Control experiments rule out SN-type mechanisms for C-N bond formation.

Photoinduced NaI‐Promoted Radical Borylation of Alkyl Halides and Pseudohalides

Main observation and conclusionA method for photoinduced NaI‐promoted radical borylation of aliphatic halides and pseudohalides with bis(catecholato)diboron (B2cat2) as the boron source is introduced. The borylation reaction is operationally simple and shows high functional group tolerance and broad substrate scope. Preliminary mechanistic studies suggest that the reaction proceeds through SN2‐based radical‐generation strategy.

Evaluation of the role of graphene-based Cu(i) catalysts in borylation reactions

A methodical experimental and theoretical analysis of different carbon-based Cu(i) materials in the context of the development of an efficient, general, scalable, and sustainable borylation reaction of aliphatic and aromatic halides has been performed.

Electroreduction of Substituted Chlorobenzenes: Understanding Silver Catalysis

It has been well established that silver electrodes are remarkable catalysts for the reduction of carbon–halogen bonds. The mechanism of electron-transfer (concerted vs. stepwise) seems to be an important aspect for silver electrocatalysis, as catalysis is only observed for concerted electron-transfer processes.1,2 For several years, it has been understood that aliphatic halides prefer concerted transfer, whereas aromatic halides prefer stepwise transfer as a result of their low-lying π* orbitals.3 However, the effect of adding various substituents to the aromatic ring on silver catalysis has not been widely studied. Indeed, preliminary studies performed in our laboratory indicate a deviation from this standard behavior; reduction of 1,2- and 1,3-dichlorobenzene at carbon and silver cathodes display remarkable catalysis at a silver surface. Moreover, these results suggest that silver is only catalytic for the first cathodic process, not the second. As a result, we propose a change in the electron transfer mechanism after the first reduction event, which is believed to be cleavage of a carbon–chlorine bond.To gain a deeper understanding of factors that influence catalysis at silver cathodes, more specifically for the reduction of substituted aromatic chlorides, the catalytic activity of silver for substituted chlorobenzenes was assessed by means of cyclic voltammetry. Voltammograms of chlorobenzene, 1,2-, 1,3-, 1,4-dichlorobenzene, and 1,2,3-, 1,2,4-, 1,3,5-trichlorobenzene were obtained at both glassy carbon and silver cathodes in dimethylformamide containing 0.10 M tetramethylammonium tetrafluoroborate. Analysis of reduction potentials reveals a moderate to significant positive potential shift, 50–200 mV, for these aromatic halides, which is indicative of electrocatalysis. References Isse, A.; Gottardello, S.; Durante, C. Dissociative electron transfer to organic chlorides: Electrocatalysis at metal cathodes. Phys. Chem. Chem. Phys. 2008, 10, 2409–2416. Isse, A.; Mussini P.; Gennaro, A. New Insights into Electrocatalysis and Dissociative Electron Transfer Mechanisms: The case of Aromatic Bromides. J. Phys. Chem. C 2009, 113, 14983–14992. Isse, A.A.; Falciola, L.; Mussini, P.R.; Gennaro, A. Relevance of electron transfer mechanism in electrocatalysis: the reduction of organic halides at silver electrodes. Chem. Commun. 2006, 334–346.

Alkylated monoterpene indole alkaloid derivatives as potent P-glycoprotein inhibitors in resistant cancer cells.

Aiming at generating a series of monoterpene indole alkaloids with enhanced multidrug resistance (MDR) reversing activity in cancer, two major epimeric alkaloids isolated from Tabernaemontana elegans, tabernaemontanine (1) and dregamine (2), were derivatized by alkylation of the indole nitrogen. Twenty-six new derivatives (3-28) were prepared by reaction with different aliphatic and aromatic halides, whose structures were elucidated mainly by NMR, including 2D NMR experiments. Their MDR reversal ability was evaluated through a functional assay, using as models resistant human colon adenocarcinoma and human ABCB1-gene transfected L5178Y mouse lymphoma cells, overexpressing P-glycoprotein (P-gp), by flow cytometry. A considerable increase of activity was found for most of the derivatives, being the strongest P-gp inhibitors those sharing N-phenethyl moieties, displaying outstanding inhibitory activity, associated with weak cytotoxicity. Chemosensitivity assays were also performed in a model of combination chemotherapy in the same cell lines, by studying the invitro interactions between the compounds and the antineoplastic drug doxorubicin. Most of the compounds have shown strong synergistic interactions with doxorubicin, highlighting their potential as MDR reversers. QSAR models were also explored for insights on drug-receptor interaction, and it was found that lipophilicity and bulkiness features were associated with inhibitory activity, although linear correlations were not observed.

Synthesis, characterization and catalytic properties of a new binuclear copper(II) complex in the azide–alkyne cycloaddition

A new binuclear copper(II)–oxalate complex containing 2,9-dimethyl-1,10-phenanthroline (dmp), was synthesized via a simple and one-pot reaction. [Cu2(dmp)2(ox)Cl2]·H2O (1) was characterized by single-crystal X-ray crystallography and IR methods. The complex 1 was been used to efficiently catalyze the three-component 1,3-Dipolar cycloaddition CuAAC reaction to produce 1,4-disubstituted 1,2,3‐triazoles in good to excellent yields from aromatic or aliphatic halide, sodium azide, and acetylene in water as a green solvent with low catalyst amount.

Green route for the synthesis of zinc oxide nanoparticles from Melia azedarach leaf extract and evaluation of their antioxidant and antibacterial activities

Zinc oxide nanoparticles (ZnO NPs) were synthesized using Melia azedarach leaf extract with zinc nitrate as initiating material. Synthesized nanoparticles shows the Ultra Violet – Visible (UV–Vis) Spectroscopy absorption peak at 372 nm which is one of the distinct features of ZnO NPs. Fourier Transform Infrared (FTIR) Spectrum implies that the role of aliphatic amines, alkyl halides and carboxylic acids were responsible for the synthesis of ZnO NPs and its stability. X- Ray Diffraction (XRD) spectrum confirmed that the synthesized zinc oxide particles were in the form of nanocrystals. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images showed hexagonal and spherical shapes of synthesized zinc oxide nanoparticles size ranges between 33 – 96 nm. The Energy Dispersive X-Ray Analysis (EDAX) confirmed that the presence of zinc content in the synthesized zinc oxide nanoparticles and it asserts that the process of biosynthesis of nanoparticles was carried out in accordance. The overall antioxidant studies revealed significant scavenging activities ranges from minimum 10.63% to maximum 54.97%. Biosynthesized ZnO NPs having efficient biological activities regarding anti-oxidant and antibacterial potential which might be utilized in several biological applications.

Recent developments and comparison of transformation strategies for organic halides to aldehydes and ketones.

Aldehydes and ketones are parts of millions of compounds and are important classes of chemicals which serve as important precursors for the synthesis of library of compounds. For the synthesis of aldehydes and ketones, one impressive approach to date, because of its excellent selectivity, high yield and stability toward over-reduction and over-oxidation, is the oxidation of organic halides (viz. aliphatic and benzyl halides). The current review covers the conventional and eco-friendly transformational approaches, from 2000 to date, toward synthesis of aldehydes and ketones from organic halides, including mechanistic studies, comparison of different transformational strategies and discussion on scope and cons and pros of each transformational approach. The review would be beneficial to get knowledge about recent synthesis techniques, select finest synthetic approach, develop further new transformational methodologies and improve current transformational approaches.

Clinochlore‐Supported Copper Nanoparticles as Green and Efficient Catalyst for Room‐Temperature Synthesis of 1,2,3‐Triazoles in Water

AbstractAcid activated clinochlore supported copper nanoparticles was prepared for the first time by immobilization of copper sulfate on clinochlore followed by in situ chemical reduction. This new material (AA‐Clin@Cu) was characterized using SEM, TEM, TGA, FTIR, XRD, XPS, and EDX and it was applied as an efficient and inexpensive catalyst for the synthesis of 1,2,3‐triazoles in water at room temperature. Using this catalyst, benzylic and aliphatic halides, as well as arylboronic acids were reacted successfully with sodium azide and alkynes. The easy synthesis and air‐stable catalyst was recycled for four runs with small drops in catalytic activity. Characterization of the reused catalyst showed similar pattern to the fresh catalyst.