Phosphonium Research Articles

Photoinduced Hydropyridylation of Dienes with Pyridyl Phosphonium Salts under Cobalt Hydride Catalysis

Photoinduced Hydropyridylation of Dienes with Pyridyl Phosphonium Salts under Cobalt Hydride Catalysis

The First Representatives of Phosphonium Salts Based on the Ammonium Acylhydrazone Scaffold: Synthesis and Biological Activity

The First Representatives of Phosphonium Salts Based on the Ammonium Acylhydrazone Scaffold: Synthesis and Biological Activity

Design and Application of Novel Sterically Hindered Phosphonium Salts in the Development of Functional Materials

Design and Application of Novel Sterically Hindered Phosphonium Salts in the Development of Functional Materials

Application of Aromatic Ring Quaternary Ammonium and Phosphonium Salts–Carboxylic Acids-Based Deep Eutectic Solvent for Enhanced Sugarcane Bagasse Pretreatment, Enzymatic Hydrolysis, and Cellulosic Ethanol Production

Deep eutectic solvents (DESs) with a hydrophobic aromatic ring structure offer a promising pretreatment method for the selective delignification of lignocellulosic biomass, thereby enhancing enzymatic hydrolysis. Further investigation is needed to determine whether the increased presence of aromatic rings in hydrogen bond receptors leads to a more pronounced enhancement of lignin removal. In this study, six DES systems were prepared using lactic acid (LA)/acetic acid (AA)/levulinic acid (LEA) as hydrogen bond donors (HBD), along with two independent hydrogen bond acceptors (HBA) (benzyl triethyl ammonium chloride (TEBAC)/benzyl triphenyl phosphonium chloride (BPP)) to evaluate their ability to break down sugarcane bagasse (SCB). The pretreatment of the SCB (raw material) was carried out with the above DESs at 120 °C for 90 min with a solid–liquid ratio of 1:15. The results indicated that an increase in the number of aromatic rings may result in steric hindrance during DES pretreatment, potentially diminishing the efficacy of delignification. Notably, the use of the TEBAC:LA-based DES under mild operating conditions proved highly efficient in lignin removal, achieving 85.33 ± 0.52% for lignin removal and 98.67 ± 2.84% for cellulose recovery, respectively. The maximum digestibilities of glucan (56.85 ± 0.73%) and xylan (66.41 ± 3.06%) were attained after TEBAC:LA pretreatment. Furthermore, the maximum ethanol concentration and productivity attained from TEBAC:LA-based DES-pretreated SCB were 24.50 g/L and 0.68 g/(L·h), respectively. Finally, the comprehensive structural analyses of SCB, employing X-rays, FT-IR, and SEM techniques, provided valuable insights into the deconstruction process facilitated by different combinations of HBDs and HBAs within the DES pretreatment.

Deep removal of dichloromethane using ionic liquids: Thermodynamic and molecular insights

In this work, the efficient capture of dichloromethane (DCM) with ionic liquids (ILs) was proposed and systematically investigated. The carboxylic acid-based anion and quaternary phosphonium cation were screened out, and on this basis the designed tetrabutylphosphonium hexanoate ([P4444][C5COO]) and tetrabutylammonium hexanoate ([N4444][C5COO]) ILs were finally synthesized. The results demonstrate that [P4444][C5COO] exhibits the optimal absorption performance (1400 mg·g−1 at 30 °C and 0.3 bar). Notably, the Henry's law constant for DCM in [P4444][C5COO] (3.02 Pa·m3·mol−1 at 25 °C) is the lowest among all solvents documented in the literature. The microscopic mechanism was explored by 1H NMR spectra, quantum chemical (QC) calculations and molecular dynamics (MD) simulations. The results suggest that anion plays a dominant role, while weak cation–anion interaction and large free volume of cations are conducive to the absorption of DCM. The proposed IL was considered as a promising alternative absorbent to achieve high absorption capacity, suitable physicochemical properties and excellent recyclability.

Wittig Synthesis, Optical Properties and Electrochemical Behaviors of Some Conjugated Derivatives of 4-Pyrones

The novel hetero-stilbene derivatives were synthesized by the Wittig reaction between 2-formyl-4-pyrones and polysubstituted imidazole-based phosphonium salts in the presence of a base. The optical properties of the products were investigated via UV–Vis absorption and fluorescent emission spectroscopy in dilute ethanol solution. Electrochemical properties were also studied by the cyclic voltammetry in CH2Cl2 solutions. The phosphorus ylides obtained from α-halocarbonyls were also condensed with 2-formyl-4-pyrone to give two electrochemically inactive and non-emitting products.

Synthesis, characterization, and theoretical studies on ylidic complexes of mercury(II) as antioxidant agents

Herein we describe the synthesis of a library of new mercury complexes, including some dimers and polymeric species. Initially, a phosphonium salt, [PPh3CH2C(O)C6H4–m-OCH3]Br (S), was synthesized from triphenylphosphine (PPh3) and BrCH2C(O)C6H4-m-OCH3 in acetone. We then reacted this phosphonium salt with an appropriate base to acquire a new phosphorus ylide monodentate, PPh3=C(H)C(O)C6H4-m-OCH3 (Y). Finally, we treated the synthesized ligand with mercury halides in dry CH3OH to form C-coordinated complexes of the form [HgX(PPh3C(H)C(O)C6H4-m-OCH3) (μ-X)]2 [X = Cl (1), Br (2), I (3)], [(PPh3=C(H)C(O)C6H4-m-OCH3)Hg(NO3)2]n (4). We characterized these compounds using CHN analysis, FT-IR, NMR (1H, 13C and 31P) and density functional theory. We elucidated the structure of 2 by single-crystal X-ray diffraction. The results establish that 1, 2 and 3 have dimeric structures, while a polymeric structure is suggested for 4. The antioxidant activity of all compounds in DMSO was assessed using a DPPH free radical scavenging method. Also, the nature of metal-ligand (C→Hg) bonding in 1, 2 and 3 have been investigated using natural bond orbital (NBO) and energy-decomposition analyses (EDA).

Phosphonium and arsonium salts based on alantolactone

The reaction of alantolactone, a sesquiterpene α,β-unsaturated lactone, with H-phosphonium or H-arsonium triflates proceeds as P–H or As–H addition at the terminal =CH2 moiety to afford novel triphenyl(sesquiterpenyl)phosponium or -arsonium triflates. Their diastereoisomerism at the formed C11 chiral center has been simulated by quantum chemical calculations.

Phosphonium salts based on 2H-imidazole: synthesis by direct C–H functionalization of imidazole N-oxides

Phosphonium salts based on 2H-imidazole: synthesis by direct C–H functionalization of imidazole N-oxides

Antimicrobial potential of quaternary phosphonium salt compounds: a review.

Given that mitochondrial dysregulation is a biomarker of many cancers, cationic quaternary phosphonium salt (QPS) conjugation is a widely utilized strategy for anticancer drug design. QPS-conjugated compounds exhibit greater cell permeation and accumulation in negatively charged mitochondria, and thus, show enhanced activity. Phylogenetic similarities between mitochondria and bacteria have provided a rationale for exploring the antibacterial properties of mitochondria-targeted compounds. Additionally, due to the importance of mitochondria in the survival of pathogenic microbes, including fungi and parasites, this strategy can be extended to these organisms as well. This review examines recent literature on the antimicrobial activities of various QPS-conjugated compounds and provides future directions for exploring the medicinal chemistry of these compounds.

Organocatalytic Dynamic Kinetic Resolution Enabled Asymmetric Synthesis of Phosphorus‐Containing Chiral Helicenes

AbstractThe catalytic asymmetric synthesis of phosphorus‐containing helicenes remains a formidable challenge, presumably due to the lack of rational design of substrates, right choice of reactions together with highly effective catalysis systems. Herein, we disclosed an efficient and practical DKR‐involving (dynamic kinetic resolution) cascade strategy toward synthesizing a novel family of phosphorus‐installing helicenes by peptide‐mimic phosphonium salt (PPS) catalysis. The sequential process of PPS‐catalyzed phospha‐Michael attack and copper salt‐facilitated aromatization led to the formation of unprecedented phosphorus‐containing oxa[5]helicene scaffolds. A wide variety of substrates bearing an assortment of functional groups were compatible with this protocol, furnishing the expected helical compounds in high yields and excellent stereoselectivities. Additionally, the helical products could be conveniently elaborated to promising phosphine ligands with perfectly retained helical chirality, which turned out to be highly efficient chiral ligands in transition metal‐catalyzed reactions. These findings not only expand the current library of phosphorus‐containing helicenes but also offer insights to explore other challenging scaffolds with molecular chirality.

Organocatalytic Dynamic Kinetic Resolution Enabled Asymmetric Synthesis of Phosphorus-Containing Chiral Helicenes.

The catalytic asymmetric synthesis of phosphorus-containing helicenes remains a formidable challenge, presumably due to the lack of rational design of substrates, right choice of reactions together with highly effective catalysis systems. Herein, we disclosed an efficient and practical DKR-involving (dynamic kinetic resolution) cascade strategy toward synthesizing a novel family of phosphorus-installing helicenes by peptide-mimic phosphonium salt (PPS) catalysis. The sequential process of PPS-catalyzed phospha-Michael attack and copper salt-facilitated aromatization led to the formation of unprecedented phosphorus-containing oxa[5]helicene scaffolds. A wide variety of substrates bearing an assortment of functional groups were compatible with this protocol, furnishing the expected helical compounds in high yields and excellent stereoselectivities. Additionally, the helical products could be conveniently elaborated to promising phosphine ligands with perfectly retained helical chirality, which turned out to be highly efficient chiral ligands in transition metal-catalyzed reactions. These findings not only expand the current library of phosphorus-containing helicenes but also offer insights to explore other challenging scaffolds with molecular chirality.

Novel Mitochondria-Targeted Amphiphilic Aminophosphonium Salts and Lipids Nanoparticles: Synthesis, Antitumor Activity and Toxicity.

The creation of mitochondria-targeted vector systems is a new tool for the treatment of socially significant diseases. Phosphonium groups provide targeted delivery of drugs through biological barriers to organelles. For this purpose, a new class of alkyl(diethylAmino)(Phenyl) Phosphonium halides (APPs) containing one, two, or three diethylamino groups was obtained by the reaction of alkyl iodides (bromides) with (diethylamino)(phenyl)phosphines under mild conditions (20 °C) and high yields (93-98%). The structure of APP was established by NMR and XRD. A high in vitro cytotoxicity of APPs against M-HeLa, HuTu 80, PC3, DU-145, PANC-1, and MCF-7 lines was found. The selectivity index is in the range of 0.06-4.0 μM (SI 17-277) for the most active APPs. The effect of APPs on cancer cells is characterized by hyperproduction of ROS and depolarization of the mitochondrial membrane. APPs induce apoptosis, proceeding along the mitochondrial pathway. Incorporation of APPs into lipid systems (liposomes and solid lipid nanoparticles) improves cytotoxicity toward tumor cells and decrease toxicity against normal cell lines. The IC50s of lipid systems are lower than for the reference drug DOX, with a high SI (30-56) toward MCF-7 and DU-145. APPs exhibit high selective activity against Gram-positive bacteria S. aureus 209P and B. segeus 8035, including methicillin-resistant S. aureus (MRSA-1, MRSA-2), comparable to the activity of the fluoroquinolone antibiotic norfloxacin. A moderate in vivo toxicity in CD-1 mice was established for the lead APP.

Frustrated Lewis pair catalyzed C–F activation of α-trifluoromethylstyrenes

A frustrated Lewis pair approach is used for the monoselective C–F activation of α-trifluoromethyl styrenes. Selective C–F activation of α-trifluoromethyl styrenes with trispentafluorophenylborane (BCF) in partnership with tri(ortho-tolyl)phosphine or 2,4,6-triphenylpyridine (TPPy) generates γ-substituted α,α-difluoropropenyl phosphonium or pyridinium salts (respectively). The ability to further functionalize such products at the α and γ-positions is demonstrated through nucleophilic substitutions and metal catalyzed Suzuki couplings to generate a range of difluoromethyl and 1,1-difluoroolefin products.

Oxygen-Containing Quaternary Phosphonium Salts (oxy-QPSs): Synthesis, Properties, and Cellulose Dissolution.

In the present study, the synthesis of oxygen-containing quaternary phosphonium salts (oxy-QPSs) was described. Within this work, structure-property relationships of oxy-QPSs were estimated by systematic analysis of physical-chemical properties. The influence of the oxygen-containing substituent was examined by comparing the properties of oxy-QPSs in homology series as well as with phosphonium analog-included alkyl side chains. The crystal structure analysis showed that the oxygen introduction influences the conformation of the side chain of the oxy-QPS. It was found that oxy-QPSs, using an aprotic co-solvent, dimethylsulfoxide (DMSO), can dissolve microcrystalline cellulose. The cellulose dissolution in oxy-QPSs appeared to be dependent on the functional group in the cation and anion nature. For the selected conditions, dissolution of up to 5 wt% of cellulose was observed. The antimicrobial activity of oxy-QPSs under study was expected to be low. The biocompatibility of oxy-QPSs with fermentative microbes was tested on non-pathogenic Saccharomyces cerevisiae, Lactobacillus plantarum, and Bacillus subtilis. This reliably allows one to safely address the combined biomass destruction and enzyme hydrolysis processes in one pot.

Palladium-Catalyzed Modular Assembly of P-Stereogenic and Axially Chiral Phosphinooxazoles (PHOX) Ligands by C-P Bond Cleavage/Intermolecular C(sp2)-H Bond Functionalization.

Chiral P,N-ligands are of great interest and importance in the fields of metal-catalyzed enantioselective transformations and have found numerous applications spanning drug and polymer synthesis. Here, modular assembly of diverse P-stereogenic and axially chiral phosphinooxazoles ligands is achieved through palladium-catalyzed asymmetric cleavage of C-P bond/intermolecular C-H bond functionalization in high atroposelectivities and diastereoselectivities of up to >99% ee and >25:1 dr. This protocol features broad substrate scope and provides an avenue for facile construction of new P-stereogenic and axially chiral phosphinooxazoles ligands directly from the phosphonium salts and benzoxazoles/benzothiazoles. Evaluation of the synthesized P-stereogenic and axially chiral phosphinooxazoles ligands in two model catalytic asymmetric reactions illustrates the potential of our strategy to access valuable chiral molecules.

Preparation and properties of vermiculite modified by triphenylbutylphosphonium bromide and PBAT composite film

AbstractIn this study, quaternary phosphonium salt (P4) was prepared, vermiculite (VMT) was modified by P4, and P4@VMT/poly (butylene adipate‐co‐terephthalate) (PBAT) composite film was prepared by the solution method. The structure of the synthesized P4 was determined by nuclear magnetic resonance and infrared. The structure and performance of P4 modified vermiculite were explored and analyzed by particle size, XRD, infrared and micro‐morphology. The structure, thermal properties, crystallization properties, rheological properties, cross‐section morphology, tensile properties and antibacterial properties of pure PBAT film and P4@VMT/PBAT composite film were tested and compared. The results show that the crystallization temperature and melting temperature of P4@VMT/PBAT composite film are higher than those of pure PBAT film. With the increase in P4@VMT content, the thermal stability of the composite film becomes worse, and the crystallization enthalpy, melting enthalpy and crystallinity also decrease, while the storage modulus, loss modulus and complex viscosity of P4@VMT/PBAT composite film increase significantly. In addition, compared with pure PBAT film, the tensile strength of P4@VMT/PBAT‐20% composites decreased by 12.0% and the elongation at break decreased by 95.7%.Highlights Successful synthesis of phosphonium quaternary P4 and modification of vermiculite. The properties of P4@VMT/PBAT composite films with different contents were studied.

Protonation Behavior of a Tetrahydrido Molybdenum(IV) Complex with Organic and Inorganic Acids

AbstractThe reaction of [MoH4(depe)2] (1) (depe=1,2‐bis(diethylphosphino)ethane) with different proton sources (HPtBu3+, C6H5COOH, C6F5COOH, H2SO4) was investigated. Whereas complete conversion of 1 into its protonated form is observed in the presence of the phosphonium salt, [MoH5(depe)2]+ only transiently forms upon treatment with the other acids. Further reactivity of the pentahydride complex is indeed noticed with the conjugated base, typically resulting in the formation of neutral (C6F5COOH, H2SO4) or cationic (PhCOOH) molybdenum dihydride complexes. The compounds were characterized by NMR spectroscopy and X‐ray crystallographic studies were performed when suitable crystals were obtained.

Photoinduced Cobalt Catalysis for the Reductive Coupling of Pyridines and Dienes Enabled by Paired Single-Electron Transfer.

Selective hydroarylation of dienes has potential to provide swift access to useful building blocks. However, most existing methods rely on dienes stabilised by an aromatic group and transmetallation or nucleophilic attack steps require electron-rich aryl coupling partners. As such, there are few examples which tolerate wide-spread heteroarenes such as pyridine. Whilst allylic C-H functionalisation could be considered an alternative approach, the positional selectivity of unsymmetrical substrates is hard to control. Here, we report a general approach for selective hydropyridylation of dienes under mild conditions using metal catalysed hydrogen-atom transfer. Photoinduced, reductive conditions enable simultaneous formation of a cobalt-hydride catalyst and the persistent radical of easily-synthesised pyridyl phosphonium salts. This facilitates selective coupling of dienes in a traceless manner at the C4-position of a wide-range of pyridine substrates. The mildness of the method is underscored by its functional group tolerance and demonstrated by applications in late-stage-functionalization. Based on a combination of experimental and computational studies, we propose a mechanistic pathway which proceeds through non-reversible hydrogen atom transfer from a cobalt hydride species which is uniquely selective for dienes in the presence of other olefins due to a much higher relative barrier associated with olefin hydrogen-atom-transfer (HAT).

Photoinduced Cobalt Catalysis for the Reductive Coupling of Pyridines and Dienes Enabled by Paired Single‐Electron Transfer**

AbstractSelective hydroarylation of dienes has potential to provide swift access to useful building blocks. However, most existing methods rely on dienes stabilised by an aromatic group and transmetallation or nucleophilic attack steps require electron‐rich aryl coupling partners. As such, there are few examples which tolerate wide‐spread heteroarenes such as pyridine. Whilst allylic C−H functionalisation could be considered an alternative approach, the positional selectivity of unsymmetrical substrates is hard to control. Here, we report a general approach for selective hydropyridylation of dienes under mild conditions using metal catalysed hydrogen‐atom transfer. Photoinduced, reductive conditions enable simultaneous formation of a cobalt‐hydride catalyst and the persistent radical of easily‐synthesised pyridyl phosphonium salts. This facilitates selective coupling of dienes in a traceless manner at the C4‐position of a wide‐range of pyridine substrates. The mildness of the method is underscored by its functional‐group tolerance and demonstrated by applications in late‐stage functionalisation. Based on a combination of experimental and computational studies, we propose a mechanistic pathway which proceeds through non‐reversible hydrogen‐atom transfer (HAT) from a cobalt hydride species which is uniquely selective for dienes in the presence of other olefins due to a much higher relative barrier associated with olefin HAT.