Phase Transfer Reagent Research Articles

Synthesis and anticancer screening of substituted (phenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide against PC3 prostate cancer cells

Multicomponent reaction among substituted isothiocyanate, hydrazine hydrate, and naphthalene-1-carbaldehyde in the presence of the phase transfer reagent Triton-B and subsequently heating lead to the formation of (Phenyl)-1-((naphthalen-5-yl)methylenethiosemicarbazide. Anticancer screening of the synthesized compound against prostate cancer cells PC3 showed that compound 2 ((Z)-4-(2-fluorophenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide), 4 ((Z)-4-(2-chlorophenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide) and 12 exhibited appreciable inhibitions on the PC3 cells. Next step evaluation of compounds on flow cytometry for apoptotic behavior revealed significant apoptosis of cancer cells by compound 12 i.e. (Z)-4-(4-chlorophenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide which necessitates its further exploration.

Synthesis of ω-Chloroalkyl Aryl Ketones via C-C Bond Cleavage of tert-Cycloalkanols with Tetramethylammonium Hypochlorite.

An oxidative C-C bond cleavage of tert-cycloalkanols with tetramethylammonium hypochlorite (TMAOCl) has been developed. TMAOCl is easy to prepare from tetramethylammonium hydroxide, and the combination of TMAOCl and AcOH effectively promoted the C-C bond cleavage in a two-phase system without additional phase-transfer reagents. Unstrained tert-cycloalkanols were transformed into ω-chloroalkyl aryl ketones in moderate to excellent yields under metal-free and mild reaction conditions.

Amphiphilic molecules affording efficient aqueous degradation of unsaturated polyester resin

Enormous challenges have been encountered in the degradation and recycling of unsaturated polyester resin (UPR) in water, primarily due to its water resistance. Herein, a novel, efficient and green catalytic system of methanesulfonic acid (MSA)/sodium laurylsulfonate (SLS) was proposed to aqueously degrade UPR under mild conditions (200°C). This method is considerably milder compared to other reported works based on aqueous hydrolysis (230°C-380°C). What's more, amphiphilic SLS as a phase transfer reagent enhanced the concentration of catalyst at the H2O-UPR interface, which facilitated the mass transfer between organic motifs with inorganic reagents and thus accelerated the reaction. The NMR and FT-IR characterizations indicated the ester bonds were cleaved via hydrolysis with H2O catalyzed by MSA, and high value-added products, i.e., copolymer of styrene and maleic anhydride (SMA) and phthalic acid (PA), were reclaimed by a simple separation process, with the yield of 86.77% and 84.37%, respectively. Furthermore, a viable mechanism for degradation was proposed through the degradation performance of the model compounds. This study provides a practical approach for the chemical degradation and conversion of other resins containing ester bonds.

Synthesis, characterization and anticancer screening of novel phenylbenzylidene thiosemicarbazone derivatives

Ten derivatives of phenylbenzylidene thiosemicarbazones (1–10) were synthesized by multicomponent reaction between hydrazine hydrate, isothiocyanate and substituted aldehydes in the presence of the phase transfer reagent Triton-B and subsequently heating the mixture. The synthesized compounds 1, 2, 5, 8 demonstrated to act as highly potent anticancer agents. They showed anticancer activity by mobilizing cellular 59Fe, inhibiting cellular uptake of 59Fe from 59Fe2-Tf, and mediating the ascorbate oxidation. Further, the structure activity relationship revealed that the donor atom and its stabilization resulted in better anticancer activity. The softness of the chelating donor atoms N and S yielded redox active iron complexes, which easily mediated ascorbate oxidation. This study identified the selective and potential chelators, which may act as anticancer agents and require further in vivo screening in future.

Self-assembly synthesis of two dimensional vanadium oxide nanotriangles for photocatalytic application

For the first time, we report a Two Dimensional Phase Transfer Reaction (2DPTR) between the three different phases of 2D nanosheets and their applications in catalysis and hydrogen evolution. Plasmonic two-dimensional (2D) nanomaterials have created a niche for themselves in a variety of applications due to their unique and tunable optical properties. In the present work, we report a simple method for the synthesis of three different phases of the 2D vanadium oxide nanosheets to convert to each other at room temperature (amorphous, nanoflakes and nanotriangles). We developed a two-step method that first involves probe ultrasonication to mediate the synthesis of 2D vanadium oxide nanoflakes (VNFs) at room temperature and secondly, their phase transformation to VNTs using hydrogen peroxide or Isopropyl Alcohol (IPA) as the phase transfer reagents. 2D VNTs have been studied for morphological, structural, and optical properties by using a variety of instruments, including TEM, UV–Vis, EPR, RAMAN, and XPS. Thus, after treatment with hydrochloric acid (HCl), the 2D vanadium oxide nanoflakes are easily converted to the 2D amorphous nanosheets (Vam) which then regain crystallinity in the form of VNTs after the addition of Hydrogen peroxide or IPA, with a plasmonic peak around 450 nm. Oxygen vacancies are created in the VNFs, after treatment with HCl, which results in the crystal lattice breakdown. These oxygen vacancies were filled up again when the nanoflakes were treated with hydrogen peroxide or IPA and then resulted in the formation of VNTs. The UV–vis spectroscopy was performed with different addition of concentrations of H2O2, the limit of detection 34.1 µM and linear range 0 to 1000 µM found. Also, a selectivity study proved H2O2 in these 2D VNTs. Vam and VNT also showed effective photocatalytic activity against KMnO4 which is a strong oxidizing reagent used in water treatment. The synthesis and plasmonic nature of the 2D VNTs and the photocatalytic activity of Vam and VNT present in this study is a pioneer report for these novel 2D nanomaterials and they can be further explored with many possibilities in many fields including sensing, catalysis, energy, biomedicine, and many other significant applications in the near future.

Amphiphilic Azo-Functionalized Polyhedral Oligomeric Silsesquioxane; Synthesis and Photo-Switched Efficient Phase Transfer via Host-Guest Encapsulation.

A new amphiphilic azo-functionalized polyhedral oligomeric silsesquioxane (POSS) derivative was synthesized by functionalizing octa(3-aminopropyl)silsesquioxane (OAS-POSS) with 4-((4-(dodecyloxy)phenyl)diazenyl)benzoic acid, affording a hydrophilic amino POSS head and hydrophobic dodecyl tail with a diphenyl-azo connector. Prepared amphiphilic azo-functionalized POSS (azo-POSS) exhibited high ability for encapsulation and transferring cationic dyes into the organic phase by vigorously mixing with aqueous solutions of each dye. The photo-controlled encapsulating properties of the synthesized phase transfer reagent was studied using cationic dyes, such as methylene blue (MB), crystal violet (CV) and thymol blue in acidic conditions. Results showed more than 95 % encapsulation of MB. However, no considerable encapsulation was shown in the case of anionic dyes such as eriochrome black T (EBT) and thymol blue in alkaline solutions. By trans/cis isomerization of the azo moiety of the phase transfer reagent by UV irradiation (365 nm), the amount of dye encapsulation was decreased, which could be attributed to the formation of cis isomer that led to the folding of the dodecyl alkyl tail on the POSS moiety, and therefore prevent to lay the 3-aminopropyl moieties of POSS head to the water/DCM interface to adsorb and encapsulate MB molecules.

Design and Discovery of Water-Soluble Benzooxaphosphole-Based Ligands for Hindered Suzuki-Miyaura Coupling Reactions with Low Catalyst Load.

We report a new class of highly effective, benzooxaphosphole-based, water-soluble ligands in the application of Suzuki-Miyaura cross-coupling reactions for sterically hindered substrates in aqueous media. The catalytic activities of the coupling reactions were greatly enhanced by the addition of catalytic amounts of organic phase transfer reagents, such as tetraglyme and tetrabutylammonium bromide. The optimized general protocol can be conducted with a low catalyst load, thereby providing a practical solution for these reactions. The viability of this new Suzuki-Miyaura protocol was demonstrated with various substrates to generate important building blocks, including heterocycles, for the synthesis of biologically active compounds.

Phase Transfer of Inorganic Nanosheets in a Water/2-Butanone Biphasic System and Lateral Size Fractionation via Stepwise Extractions.

Lateral size fractionation of niobate nanosheets derived from K4Nb6O17·3H2O was achieved via phase transfer from the aqueous phase to the 2-butanone phase in a water/2-butanone biphasic system, in which tetra-n-dodecylammonium (TDDA+) bromide was used as a phase transfer reagent. Phase transfer of the nanosheets was observed when the TDDA+/[Nb6O17]4- molar ratios were 0.6 and 1.0, and the phase transfer ratios were 41 and 97%, respectively. FT-IR and thermogravimetry results showed that the extracted nanosheets contained TDDA+ ions. These results indicate that adsorption of TDDA+ likely induced an increase in the hydrophobicity of the nanosheet surface, leading to phase transfer. In the AFM image of the original nanosheets in the aqueous phase, their lateral sizes were in the range from several hundreds of nm to several tens of μm, while those of the nanosheets after phase transfer at a molar ratio of 0.6 were in the range from several hundreds of nm up to 2 μm, indicating that nanosheets with smaller lateral sizes were preferentially extracted into the 2-butanone phase. In addition, the phase transfer ratio of the fragmentated nanosheets with a much smaller lateral size distribution compared with the original nanosheets was 79% when the TDDA+/[Nb6O17]4- molar ratio was 0.6, indicating that phase transfer for the nanosheets with smaller lateral sizes proceeded efficiently. Following this extraction cycle, the nanosheets with a TDDA+/[Nb6O17]4- molar ratio of 0.6 remaining in the aqueous phase after extraction were extracted stepwise again through dilution of the aqueous phase with water and the addition of a fresh 2-butanone solution of tetra-n-dodecylammonium bromide to form a new biphasic system. The lateral sizes of the nanosheets increased as the extraction cycles were repeated. Completion of the three extraction cycles allowed formation of the three classes of the nanosheets with different lateral size ranges of 0.68 ± 0.5, 2.8 ± 1.9, and 6.6 ± 3.1 μm.

Highly effective liquid and solid phase extraction methods to concentrate radioiodine isotopes for radioiodination chemistry.

Radioactive iodine isotopes play a pivotal role in radiopharmaceuticals. Large-scale production of multi-patient dose of radioiodinated nuclear medicines requires high concentration of radioiodine. We demonstrate that tetrabutylammonium chloride and methyltrioctylamonium chloride are effective phase transfer reagents to concentrate iodide-124, iodide-125 and iodide-131 from the corresponding commercial water solutions. The resulting concentrated radioiodide, in the presence of either phase transfer reagent, does not hamper the chemical reactivity of aqueous radioiodide in the copper (II)-mediated one-pot three-component click chemistry to produce radioiodinated iodotriazoles.

Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis.

The two‐electron reduced forms of perylene diimides (PDIs) are luminescent closed‐shell species whose photochemical properties seem underexplored. Our proof‐of‐concept study demonstrates that straightforward (single) excitation of PDI dianions with green photons provides an excited state that is similarly or more reducing than the much shorter‐lived excited states of PDI radical monoanions, which are typically accessible after biphotonic excitation with blue photons. Thermodynamically demanding photocatalytic reductive dehalogenations and reductive C−O bond cleavage reactions of lignin model compounds have been performed using sodium dithionite acts as a reductant, either in aqueous solution or in biphasic water–acetonitrile mixtures in the presence of a phase transfer reagent. Our work illustrates the concept of multi‐electron reduction of a photocatalyst by a sacrificial reagent prior to irradiation with low‐energy photons as a means of generating very reactive excited states.

Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis

AbstractThe two‐electron reduced forms of perylene diimides (PDIs) are luminescent closed‐shell species whose photochemical properties seem underexplored. Our proof‐of‐concept study demonstrates that straightforward (single) excitation of PDI dianions with green photons provides an excited state that is similarly or more reducing than the much shorter‐lived excited states of PDI radical monoanions, which are typically accessible after biphotonic excitation with blue photons. Thermodynamically demanding photocatalytic reductive dehalogenations and reductive C−O bond cleavage reactions of lignin model compounds have been performed using sodium dithionite acts as a reductant, either in aqueous solution or in biphasic water–acetonitrile mixtures in the presence of a phase transfer reagent. Our work illustrates the concept of multi‐electron reduction of a photocatalyst by a sacrificial reagent prior to irradiation with low‐energy photons as a means of generating very reactive excited states.

Promoting electron transfer of surface oxygen vacancies in Pd/CeO2-RE via doping engineering for enhancing catalytic activity in Suzuki coupling reaction

Doping engineering is considered as a facile and effective method for improving the physical and chemical properties of CeO2. Herein, rare earth (RE) ions (La and Nd) doped Pd/CeO2 with the coaxial double-nanotube structure were manufactured by the electrospinning and high-temperature calcination. Through the doping engineering, the original morphologies of Pd/CeO2 were not destroyed and all the elements were uniformly distributed on the surface of nanotubes. XRD, Raman and UV–vis characterizations revealed that La3+ and Nd3+ ions were incorporated into the CeO2 lattice, while the cubic fluorite structure of CeO2 was maintained. Moreover, it has been proved that there were oxygen vacancies existed on the surface of CeO2 and the concentration of oxygen vacancies increased significantly as the radius of RE ions increases. In addition, an electron transfer pathway between CeO2 and Pd nanoparticles was proposed based on the experimental data and Density Functional Theory (DFT) calculations. The Pd/CeO2-La catalyst with abundant oxygen vacancies showed a high catalytic performance for Suzuki coupling reaction under mild conditions without any phase-transfer reagent, toxic solvent and inert protective atmosphere, which realizing the green catalysis.

Formation and Application of Core-Shell of FePt-Au Magnetic-Plasmonic Nanoparticles.

Monodispersed FePt core and FePt–Au core–shell nanoparticles (NPs) have been chemically synthesized in liquid solution and with controllable surface-functional properties. The NP size was increased from 2.5 nm for FePt to 6.5 nm for FePt–Au, which could be tuned by the initial concentration of gold acetate coated onto FePt seeding NPs via a seed-mediated formation of self-assembled core–shell nanostructures. The analyses of the interplanar spacing obtained from the high-resolution transmission electron microscopy (HRTEM), selective electron diffraction pattern (SAED), and x-ray diffraction (XRD) confirmed that both FePt core and Au shell belong to the face-centered cubic (fcc) structure. FePt–Au NPs have a surface plasmon resonance (SPR) peak at 528 nm in the visible optical band region, indicating the red shift compared with the typical theoretical value of 520 nm of pure Au NPs. The surface modification and ligand exchange of FePt–Au was using mercaptoacetic acid (thiol) as a phase transfer reagent that turned the NPs hydrophilic due to the functional carboxyl group bond on the surface of presented multifunctional magnetic–plasmonic NPs. The water-dispersible FePt-based NPs conjugated with biomolecules could reach the different biocompatibility requirements and also provide enough heating response that acted as a potential agent for magnetic fluid hyperthermia in biomedical engineering research fields.

Selective extraction of trivalent actinides using CyMe4BTPhen in the ionic liquid Aliquat-336 nitrate.

The extraction of Am(iii), Cm(iii) and Eu(iii) by 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) from nitric acid solution was studied using the ionic liquid Aliquat-336 nitrate ([A336][NO3]) as diluent. Results show a high selectivity of the solvent for Am(iii) and Cm(iii) over Eu(iii), but rather slow extraction kinetics. The kinetics of CyMe4BTPhen were largely improved by the addition of 0.005 mol L−1N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA) as a phase transfer reagent and by the use of 1-octanol as co-diluent. The addition of the phase transfer catalyst and co-diluent did not compromise the selectivity towards the actinide/lanthanide separation and thus this four-component system can be successfully applied to separate Am(iii) and Cm(iii) from the lanthanides.

Selective Phase Transfer Reagents (OxP-crowns) for Chromogenic Detection of Nitrates Especially Ammonium Nitrate.

Nitrogen and phosphorus-containing ions such as ammonium, nitrates and phosphates are anthropogenic pollutants while ammonium nitrate may be diverted for nefarious purposes in improvised explosive devices. Crown ether-oxoporphyrinogen conjugates (OxP-crowns) are used to selectively detect nitrates, especially their ion pairs with K+ and NH4 + , based on ion pair complexation of OxP-crowns under phase transfer conditions. The presence of phosphate and carbonate lead to deprotonation of OxP-crowns. OxP-1N18C6 is capable of extracting ion pairs with nitrate from aqueous phase leading to a selective chromogenic response. Deprotonation of the OxP moiety leads to [OxP- ]-1N18C6[K+ ] and is promoted by crown ether selective cation binding coupled with hydration of basic oxoanions, which are constrained to remain in the aqueous phase. This work illustrates the utility of molecular design to exploit partitioning and ion hydration effects establishing the selectivity of the chromogenic response.

Cover Feature: Selective Phase Transfer Reagents (OxP‐crowns) for Chromogenic Detection of Nitrates Especially Ammonium Nitrate (Chem. Eur. J. 58/2020)

A color-based detector for ammonium nitrate consists of crown ether-appended oxoporphyrinogens, the OxP-Crowns, which extract ion pairs into an organic phase based on cation binding at crown ether and anion complexation. Selective mauve chromogenic response is observed when ammonium nitrate, commonly used in improvised explosive devices, is extracted from water to chloroform providing a simple test. As illustrated, a network of responses is found when considering other anions and aqueous phase pH. More information can be found in the Full Paper by J. P. Hill et al. on page 13177.

One-pot synthesis of alkynylthiocyanates by phase-transfer reagent

Thiocyano-group widely exist in natural products and drug structures. A novel one-pot synthesis of alkynylthiocyanates from terminal alkynes, [hydroxy(tosyloxy)iodo]benzene and potassium thiocyanate by phase-transfer reagent involving the hypervalent iodine intermediates in transition metal-free conditions was developed. The internal alkynylthiocyanates could be used to synthesize some important compounds such as 5-thiocyanato-1,2,3-triazoles and (Z)-α-thiocyanato-vinyl trifluoromethanesulfonate.

Poly(alkyl/arylphosphazene)-Metal Nanoparticle Composites

Nanoparticles of gold were prepared by reduction of Au(III) with a reducing agent in the presence of poly(methylphenylphosphazene), [Me(Ph)PN]n, (PMPP), an alcohol derivative (PMPP-OH), a graft copolymer poly(methylphenylphosphazene)-graft-polystyrene, PMPP-g-PS, and a blend of the two graft components. The process involved no phase transfer reagents because the polymers successfully moved the salts from the aqueous to the organic phase. The metal nanoparticles were characterized by UV–Visible spectroscopy and transmission electron microscopy (TEM). When stabilized by these phosphazene polymers, the average size of gold nanoparticles was between 3 and 5 nm. The PMPP-OH nanocomposites were stable in toluene at room temperature for several days, and showed no change on heating in the absence of solvent at 100 °C. In the graft copolymer and the blend, TEM imaging shows that the nanoparticles of gold were located exclusively in the phosphazene domains. An improved synthesis of the parent polymer, PMPP, used to make these and many other derivatives is described.

Fabrication of multi-walled carbon-nanotube-grafted polyvinyl-chloride composites with high solar-thermal-conversion performance

The optical absorption properties of carbon nanotubes (CNTs) have attracted extensive research attention. Here we report the fabrication of sea-island structured polymer-based multi-walled CNT (MWNT) composite with high solar-thermal-conversion performance. MWNT-grafted 4-chloromethyl styrene (MWNTs-g-CMS) is prepared via esterification between carboxyl groups on the MWNT surface and the chloromethyl group of the CMS in the presence of a phase-transfer reagent in water. Covalent bonding between the CMS and the MWNTs is confirmed by Fourier transform infrared spectra. Thermogravimetric analysis of the MWNTs-g-CMS shows a mass percentage of the attached methyl styrene chains as high as 24.31 wt%. Subsequently, polymer-based MWNT-graft-polyvinyl-chloride (MWNTs-g-PVC) composite was prepared via an in-situ graft polymerization between the vinyl chloride and active styryl groups of the MWNTs-g-CMS. The MWNT grafting efficiencies in a series of MWNTs-g-PVC composites are 0.013–0.103%. The sea-island structure of the MWNTs-g-PVC composites and the fine dispersion of MWNTs in the island are verified by electron microscopy. The solar-thermal conversion performance of the MWNTs-g-PVC composites is studied. The composites exhibit excellent light-absorption properties that resemble a black body, and yield a higher solar-thermal conversion efficiency than the carboxylic MWNT (PVC/MWNTs-COOH) composites, which is attributed to the sea-island structure and the good dispersion of MWNTs in the islands.

Biomimetic Clauson‐Kass and Paal‐Knorr Pyrrole Synthesis Using β‐Cyclodextrin‐SO3H under Aqueous and Neat Conditions ‐ Application to Formal Synthesis of Polygonatine†

AbstractThe synthesis of pyrroles under mild conditions using sulfonic acid‐functionalized β‐Cyclodextrin (β‐CD) as a supramolecular catalyst under aqueous conditions is demonstrated. Good to excellent conversion of various amines into pyrroles was observed without any side product formation. CD was found to play a dual role as a phase transfer reagent through inclusion as well as an acid catalyst thereby facilitating the smooth conversions of reactants. The advantages of this protocol are mild reaction conditions, sustainable catalyst and use of non‐toxic solvent water. Notably, the catalyst can be easily recovered and reused up to five cycles without any loss of catalytic activity. The developed protocol was successfully used as a key step for the formal synthesis of the alkaloid natural product Polygonatine.