Phosphonium Research Articles

Aerobic Coupling of Organophosphonium Salts with Alkenes: Catalyst‐Free C(sp3)−C(sp2) Bond Formation

AbstractAn aerobic coupling of benzhydryl phosphonium salts with simple alkenes for accessing trisubstituted olefins is developed under metal‐free, catalyst‐free, and additive‐free conditions. New C(sp3)−C(sp2) bond is constructed via the C−P and C−H bond functionalization by synergistically using O2 as a “green” oxidant and DMSO as a promoter. The method also distinguishes itself by its broad substrate scope and synthetic potential. Particularly, the use of 1,3,5‐trimethoxybenzene fragment in the resulting products as a carbon‐based leaving group for further transformations is proved to be feasible.

Multi-dimensional application of quaternary phosphonium salt functionalized fiber with high polarization performance: Efficient adsorption of SDBS and green conversion of CO2

A novel mono-quaternary phosphorus salt functionalized fiber (PANQPSF) was developed as the multifunctional material to simultaneously realize selective removal of sodium dodecyl benzene sulfonate (SDBS) from water and green conversion of CO2. Compared with other adsorption materials and functionalized fibers, PANQPSF exhibits the eminent adsorption performance for SDBS due to its high polarization and hydrophobicity, and the adsorption capacity can reach 5.1 mol mol−1, equivalenting to 1066 mg g−1. And the synergistic adsorption mechanism of electrostatic interaction and lipophilic interaction between PANQPSF and SDBS is proposed. Furthermore, the PANQPSF still keeps excellent adsorption capacity even after 10 cycles. More satisfactorily, PANQPSF is used to catalyze the cycloaddition reaction of CO2 and epoxy compounds. The catalytic mechanism based on the nucleophilicity of Br− and the stabilizing effect of electrostatic interaction is promoted. In summary, the adsorption and catalytic performance prove that PANQPSF is an outstanding material with multi-dimensional applications.

Visible-Light-Induced Photoreduction of Carborane Phosphonium Salts: Efficient Synthesis of Carborane-Oxindole-Pharmaceutical Hybrids.

Visible-light-induced photoreaction of carboranes is an effective approach to prepare carborane-containing compounds. While several methods involving boron-centered carboranyl radicals have been established, those for carbon-centered carboranyl radicals are underdeveloped, except for the UV-light-promoted photohomolysis. Herein, we describe a simple but effective approach to access carbon-centered carboranyl radicals by photoreduction of carborane phosphonium salts under blue light irradiation without using transition metals and photocatalysts. The utility of the method was demonstrated by successfully preparing a range of carborane-oxindole-pharmaceutical hybrids by radical cascade reactions. Computational and experimental studies suggest that the carbon-centered carboranyl radicals are generated by single-electron transfer of the photoactive charge-transfer complexes between the salts and the additive potassium acetate.

Visible‐Light‐Induced Photoreduction of Carborane Phosphonium Salts: Efficient Synthesis of Carborane‐Oxindole‐Pharmaceutical Hybrids

AbstractVisible‐light‐induced photoreaction of carboranes is an effective approach to prepare carborane‐containing compounds. While several methods involving boron‐centered carboranyl radicals have been established, those for carbon‐centered carboranyl radicals are underdeveloped, except for the UV‐light‐promoted photohomolysis. Herein, we describe a simple but effective approach to access carbon‐centered carboranyl radicals by photoreduction of carborane phosphonium salts under blue light irradiation without using transition metals and photocatalysts. The utility of the method was demonstrated by successfully preparing a range of carborane‐oxindole‐pharmaceutical hybrids by radical cascade reactions. Computational and experimental studies suggest that the carbon‐centered carboranyl radicals are generated by single‐electron transfer of the photoactive charge‐transfer complexes between the salts and the additive potassium acetate.

Preparation and Characterization of Antibacterial Polycarbonate (PC) Using High Thermal Resistant Quaternary Fluoroalkyl Phosphonium Salts as Antibacterial Agents

In our previous study, quaternary fluoroalkyl phosphonium salt with iodine anion (PPICF-13) was synthesized as an antibacterial agent for PC, but it would dye PC to be brown during processing because of the oxidation of the iodine. With the aim to eliminate the dyeing problem, three quaternary fluoroalkyl phosphonium salts (PPCF) with trifluoroacetate (TFA-PPCF-13), tetrafluoroborate (FB-PPCF-13), and trifluoromethanesulfonate (TFMS-PPCF-13) were synthesized in the research described here through anion exchange reactions between PPICF-13 with the relative silver salts. After evaluation of their antibacterial activity and thermal stability, FB-PPCF-13 was chosen to prepare antibacterial PC through injection processing. The influence of FB-PPCF-13 concentration on the mechanical properties, thermodynamic properties, light transmittance, appearance, and antibacterial activity of the antibacterial PC was investigated. The results showed that incorporation of FB-PPCF-13 had no negative influence on the mechanical properties of PC, but could reduce Tg and increase the MFI due to the plasticization effect of FB-PPCF-13. When the concentration of FB-PPCF-13 was 2 wt.% or more, the resulting antibacterial PC could have strong antibacterial activity no matter before or after being aged. Though FB-PPCF-13 reduced the light transmittance of PC, it did not influence the color scheme of dyed PC products.

Effect of the structure of chitosan quaternary phosphonium salt and chitosan quaternary ammonium salt on the antibacterial and antibiofilm activity

N-(4-N′, N′, N′-trimethylphosphonium chloride) benzoyl chitosan (TMPCS), N-(4-N′, N′, N′-triphenylphosphonium chloride) benzoyl chitosan (TPPCS), and N-(4-N′, N′, N′-trimethylmethanaminium chloride) benzoyl chitosan (TMACS) were synthesized. The structures of the products were characterized by Fourier transform infrared spectroscopy, Nuclear magnetic resonance spectroscopy and ultraviolet-visible spectroscopy. Their antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were investigated in vitro using the antibacterial rate, minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the antibiofilm activity was investigated by crystal violet assay. The antibacterial assessment revealed that the chitosan quaternary phosphonium salts of similar structure had superior antibacterial activity than chitosan quaternary ammonium salt. The antibacterial rate of CS, TMPCS, TPPCS and TMACS against E. coli at 0.5 mg/mL was 10.4 %, 42.0 %, 58.5 % and 21.6 % respectively. At the same concentration, the antibacterial rate of TMPCS, TPPCS and TMACS against S.aureus was all up to 100 %. The biofilm inhibition rate of CS, TMPCS, TPPCS and TMACS at a half of MIC against E.coli was 28.4 %, 33.9 %, 56.6 % and 57.6 % respectively, and against S.aureus was 30.8 %, 53.8 %, 62.2 % and 58.5 % respectively. The biofilm removal rate of CS, TMPCS, TPPCS, TMACS against E.coli at 2.5 mg/mL was 20.6 %, 46.4 %, 48.9 % and 41.6 % respectively, and against S.aureus at 2.5 mg/mL was 41.5 %, 60.4 %, 69.9 % and 59.01 % respectively.

New Morita-Baylis-Hillman (MBH) phosphonium salts from alcohols to the synthesis of 2-alkenyl- and 2-alkylidenecyclohexenones

Most of synthetic methods for 2- and 3-cyclohexenone derivatives start from limited substrates and therefore their efficiency still limited. In this paper, we report a general synthetic approach for such derivatives using MBH adducts, as substrates easily synthesized under standard conditions. For this purpose, a one-pot conversion of MBH alcohols into the corresponding phosphonium salts is carried out in high yields using PPh3 and an aqueous solution of HBr (48%), both at room temperature. Following purification and characterization of the title products, their further treatment at room temperature with either RCHO/tBuOK or only tBuOK, as the base, yields the corresponding 2-alkenyl- and 2-alkylidenecyclohexenones in good yields through Wittig olefinations or δ-elimination reactions of PPh3.HBr.

Asymmetric Synthesis of Contact Pheromone Component of Xylotrechus colonus and Its Analogues

AbstractXylotrechus colonus is an abundant wood‐boring pest of woody plants. 3‐Methylpentacosane was identified as the component of its contact pheromone. A novel and efficient asymmetric synthesis of (S)‐3‐methylpentacosane and its analogues was developed using (S)‐2‐methylbutan‐1‐ol as chiral source. The key of this approach included Wittig coupling of chiral phosphonium salt with aldehyde, Pd‐catalyzed hydrogenation and Appel reaction. Our synthesis would be helpful for the control and detect of this pest.

Application of Phosphoranyl Radical in Organic Synthesis

Many useful organic reactions have been developed by taking advantage of the high affinity of phosphorus atoms with some heteroatoms such as oxygen and sulfur atoms. Although the reactions proceed via phosphorus ylides, phosphonium salts and phosphoranyl radicals as active species, the reactions via phosphoranyl radicals are only a few reports. In this short review, the three reactions via phosphoranyl radicals reported recently are described.

Effect of Composition on Adhesion and Chemical Resistance in Multilayer Elastomer Laminates

The defense against dangerous chemical agents imposes demanding requirements for the development of protective materials, such as elastomers, plastics, and fabrics. While chemical protective clothing is commercially available, its elasticity, flexibility, stretchability, and chemical resistance spectrum may be restrictive and in need of further improvement. In this paper, a multilayer elastomer laminate, consisting of bromobutyl rubber (BIIR), acrylonitrile-butadiene rubber (NBR), and a fluoroelastomer (FKM), was fabricated to meet broad-range protection against chemical agents, while remaining flexible and stretchable. The bonding between the multiple layers was investigated via formulations designed to promote interlayer adhesion. The effects of magnesium oxide (MgO), zinc oxide (ZnO), stearic acid, carbon black, and phosphonium salt on the vulcanization and adhesion of the BIIR–NBR–FKM laminate were systematically studied using cure rheometry and T-peel tests. The optimized formulations of each rubber yielded adhesion strengths of 19 N/2.5 cm and >65 N/2.5 cm for the BIIR–NBR laminate and NBR–FKM laminate, respectively. The chemical resistance of these three elastomer sheets and their strongly bonded laminates was measured according to ASTM F739 and the time-lag method for methyl ethyl ketone, toluene, and butylamine. The laminates showed excellent resistance to the selected chemicals, with detected breakthrough times of longer than 1000 min. Also, some laminates were observed to have longer breakthrough times than the equivalent thickness of the individual elastomers making up the laminate.

Ring-opening copolymerization of CO2 with epoxides catalyzed by binary catalysts containing half salen aluminum compounds and quaternary phosphonium salt

The synthesis and characterization of two different categories of Al(III) compounds supported by unsymmetrical phenoxy-imine ligands with furan-2-ylmethanimine and thiophen-2-ylmethanimine side arms is described. Reactions of the ligands with Al(CH3)3 in a 1:1 and 2:1 stoichiometric ratio resulted in the formation of the corresponding monosubstituted and disubstituted Al(III) compounds in quantitative yields. These compounds were fully characterized using various spectroscopic techniques and elemental analysis. Single-crystal X-ray diffraction studies revealed that the Al(III) center in the monosubstituted compounds adopt a distorted tetrahedral geometry while those in the disubstituted compounds adopt a distorted trigonal bipyramidal geometry with a geometric index τ = 0.72. These compounds along with tetraphenylphosphonium chloride (TPPCl) form a binary catalyst system for the ring-opening copolymerization (ROCOP) of CO2 with cyclohexene oxide (CHO) and propylene oxide (PO). They show notable activity producing alternating polycarbonate with TOF up to 107 h−1 and high selectivity (carbonate linkages > 80%). The catalytic activities of the compounds have been investigated by varying the substituent in the phenolate core and in the imine backbone.

Facile Functionalization of Charcoal by a Green Approach

The ability of charcoal, a low-cost material derived from biomass pyrolysis, to be functionalized via cation exchange in an aqueous solution, providing new interesting fillers with possible antimicrobial and flame-retardant properties, is discussed here. The adducts obtained through this sustainable procedure, show a significant uptake of close to 30% by weight of well-known quaternary phosphonium salts, tetraphenyl phosphonium bromide, and dodecyl triphenyl phosphonium bromide. The new functionalized materials were characterized by elemental analysis, wide-angle X-ray diffraction, infrared spectroscopy, and thermogravimetry. Additionally, a study of changing the ratio between the reagents for both adducts was performed to improve salt uptake and optimize the cationic exchange. Dispersibility tests showed the ability of functionalization to deeply change the polarities of the carbon materials to modify the compatibility and improve the possible interactions with different media, such as different polymer matrices.

From a Fluorenyl Substituted Ylide-Functionalized Phosphine to a Neutral Phosphide via P-C Bond Cleavage.

Bulky ylide-substituted phosphines have recently found application as potent ligands in homogeneous catalysis. The attempted synthesis of the ylide-substituted fluorenylphosphine YPh P(Cy)Flu [YPh =Cy3 P(Ph)C; Flu=9-methylfluorenyl] now resulted in the unexpected elimination of 9-methylenefluorene during the deprotonation step of the intermediary α-phosphino phosphonium salt to yield the secondary ylide-substituted phosphine YPh P(Cy)H. This phosphine underwent formal H2 elimination under basic conditions to form a cyclic phosphonium ylide with a P-C-P-C four-membered ring via deprotonation of one cyclohexyl group of the PCy3 moiety. Upon coordination to transition metals the secondary ylidylphosphine forms a neutral phosphide ligand by shift of the proton into the ylide-backbone and formation of zwitterionic metal complexes.

Preparation and characterization of functionalized chitosan/polyvinyl alcohol composite films incorporated with cinnamon essential oil as an active packaging material

In this study, amphiphilic chitosan (NPCS-CA) was synthesized by grafting quaternary phosphonium salt and cholic acid onto the chain of chitosan, aiming to develop an active edible film based on NPCS-CA and polyvinyl alcohol (PVA) incorporated with cinnamon essential oil (CEO) by the casting method. The chemical structure of the chitosan derivative was characterized by FT-IR, 1H NMR and XRD. Through the characterization of FT-IR, TGA, mechanical and barrier properties of the composite films, the optimal proportion of NPCS-CA/PVA was determined as 5/5. And, the tensile strength and elongation at break of the NPCS-CA/PVA (5/5) film with 0.4 % CEO were 20.32 MPa and 65.73 %, respectively. The results revealed that the NPCS-CA/PVA-CEO composite films exhibited an excellent ultraviolet barrier property at 200–300 nm and significantly reduced oxygen permeability, carbon dioxide permeability and water vapor permeability. Furthermore, the antibacterial property of film-forming solutions against E. coli, S. aureus, and C. lagenarium was distinctly improved with the increase of NPCS-CA/PVA proportion. And, the multifunctional films effectively extended the shelf-life of mangoes at 25 °C based on the characterization of surface changes and quality indexes. The NPCS-CA/PVA-CEO films could be developed as biocomposite food packaging material.

Synthesis of arsonium salts and betaines based on triphenylarsine and ω-bromoalkanoic acids

The reactions between Ph3As and ω-bromoalkanoic acids with the length of polymethylene fragment n = 5, 7, 9 afford quaternary arsonium salts. Their treatment with alkali gives biologically active arsenobetaines. Solvent-free reactions of Ph3P or Ph3As with 2,3-dibromopropionic acid lead to the corresponding arsonium and phosphonium salts bearing (CH2)2COOH substituent.

Recent Asymmetric Phase-Transfer Catalysis with Chiral Binaphthyl-Modified and Related Phase-Transfer Catalysts over the Last 10 Years.

In this personal account, we describe our recent advances in the three types of phase-transfer catalysis for various transformations including asymmetric induction: Firstly, asymmetric phase-transfer catalysis with Maruoka-type C2 -symmetric chiral biaryl-modified tetraalkylammonium salts and phosphonium salts; Secondly, asymmetric phase-transfer catalysis under base-free and neutral conditions; Thirdly, hydrogen-bonding catalysis using tetraalkylammonium and trialkylsulfonium salts. These three different strategies are illustrated by using various phase-transfer catalyzed transformations.

The Use of Polymer Membranes for the Recovery of Copper, Zinc and Nickel from Model Solutions and Jewellery Waste.

A polymeric inclusion membrane (PIM) consisting of matrix CTA (cellulose triacetate), ONPPE (o-nitrophenyl pentyl ether) and phosphonium salts (Cyphos 101, Cyphos 104) was used for separation of Cu(II), Zn(II) and Ni(II) ions. Optimum conditions for metal separation were determined, i.e., the optimal concentration of phosphonium salts in the membrane, as well as the optimal concentration of chloride ions in the feeding phase. On the basis of analytical determinations, the values of parameters characterizing transport were calculated. The tested membranes most effectively transported Cu(II) and Zn(II) ions. The highest recovery coefficients (RF) were found for PIMs with Cyphos IL 101. For Cu(II) and Zn(II), they are 92% and 51%, respectively. Ni(II) ions practically remain in the feed phase because they do not form anionic complexes with chloride ions. The obtained results suggest that there is a possibility of using these membranes for separation of Cu(II) over Zn(II) and Ni(II) from acidic chloride solutions. The PIM with Cyphos IL 101 can be used to recover copper and zinc from jewellery waste. The PIMs were characterized by AFM and SEM microscopy. The calculated values of the diffusion coefficient indicate that the boundary stage of the process is the diffusion of the complex salt of the metal ion with the carrier through the membrane.

PAEK- and PES-like perarylated phosphonium ionenes: Synthesis, thermal properties, and conductivity

Perarylated phosphonium salts are known to exhibit high degrees of thermal stability, often in excess of 400 °C. Here, the thermal and conductive properties of a series of perarylated phosphonium ionenes, prepared utilizing a PAEK-/PES-like synthetic approach, is described. All of the ionenes were found to display Td5% values in excess of 365 °C. Structural changes in the polymer backbone were found to have a prominent impact on Tg, with the meta-analogs exhibiting values ∼45 °C below the para-analogs, emphasizing the significant impact that solid-state packing can have on thermal transitions. All of the phosphonium ionenes were found to be resistant to decomposition under caustic conditions (NaOH), even at elevated temperature (60 °C) over a period of 48 h. Ionic conductivities were on the order of ∼10−7 S/cm at 120 °C, with the meta-analogs exhibiting a 1-2 orders-of-magnitude enhancement compared to their para-analogs, indicating that disruption of chain packing can lead to improvements in ionic conductivity while maintaining relatively high thermal and chemical resistance.

Nickel-catalyzed Suzuki cross-coupling reaction of alkyl triaryl phosphonium salts

The Suzuki cross-coupling reaction of triphenyl quaternary phosphonium triflates with boronic acids was reported. The reaction was catalyzed by Ni(COD)2 without additional ligand, using Cs2CO3 as the base in toluene, and various biphenyls were synthesized in medium to excellent yields. This protocol has a wide adaptability to boronic acids, and many functional groups are tolerated. The method is scalable and could be performed on the gram scale. The regioselective arylation of differently substituted phenyl phosphonium triflates was observed at the side of electron-deficient phenyl group.

Towards Axially Chiral Pyrazole-Based Phosphorus Scaffolds by Dipeptide-Phosphonium Salt Catalysis.

Given the comparatively lower rotational barriers, the catalytic asymmetric construction of axially chiral biaryl structures, especially those containing a five-membered heterocycle, still remains a challenge. Herein, we described a general and modular protocol to access atropisomeric arylpyrazole scaffolds containing a phosphorus unit by a dipeptide phosphonium salt catalyzed reaction involving an oxidative central-to-axial chirality conversion. This reaction features excellent yields and enantioselectivities, broad substrate scope, and a low catalyst loading, delivering axially chiral phosphine compounds.