Phosphorus Moiety Research Articles

Near-Infrared Phosphorus-Substituted Rhodamine with Emission Wavelength above 700 nm for Bioimaging.

Phosphorus has been successfully fused into a classic rhodamine framework, in which it replaces the bridging oxygen atom to give a series of phosphorus-substituted rhodamines (PRs). Because of the electron-accepting properties of the phosphorus moiety, which is due to effective σ*-π* interactions and strengthened by the inductivity of phosphine oxide, PR exhibits extraordinary long-wavelength fluorescence emission, elongating to the region above 700 nm, with bathochromic shifts of 140 and 40 nm relative to rhodamine and silicon-substituted rhodamine, respectively. Other advantageous properties of the rhodamine family, including high molar extinction coefficient, considerable quantum efficiency, high water solubility, pH-independent emission, great tolerance to photobleaching, and low cytotoxicity, stay intact in PR. Given these excellent properties, PR is desirable for NIR-fluorescence imaging in vivo.

ChemInform Abstract: Nickel‐Catalyzed One‐Pot Tandem 1,4‐1,2‐Addition of P(O)H Compounds to 1,10‐Phenanthrolines.

A novel and efficient nickel-catalyzed tandem 1,4-1,2-addition of P(O)H compounds to 1,10-phenanthrolines forming various 2,4-diphosphono-1,2,3,4-tetrahydro-1,10-phenanthrolines has been developed. This reaction breaks up the aromatic stabilization and directly introduces two phosphorus moieties in one single step. This finding is the first example of transition-metal-catalyzed double hydrophosphonylation of 1,10-phenanthrolines.

Potential use of native fungal strains for assisted uranium retention

Uranium-stabilizing ligands can be useful complexing agents for uranium in aqueous solution. The discovery of novel ligand candidates for selective uranium capture in artificial and natural waters could provide scope for their use in water remediation and metal recovery from low- and high grade ores. In this study we used seven fungal strains, isolated from shale waste, to monitor the uranium retention capacity from an aqueous solution. After four weeks of incubation, suspensions containing the fungal strains were filtered, and up to 100% of the total uranium inventory was removed from a 10mgL−1 solution. Approximately 70% of the total uranium removal is attributed to complexation and/or adsorption by particles in the malt extract and some 10% is adsorbed by the fungal biomass. The additional 20% uranium removed could be related to the excretion of fungal metabolites. From 58% to 90% of the uranium is removed within ten minutes. The formation of colloidal/particulate uranium is proposed to be controlled by organic ligands in the culture medium and organic ligands excreted by the fungi where phosphorus moieties seem to be important. Membrane fouling by the hydrocarbons is also suggested to contribute to a loss of uranium from the aqueous phase.

Symmetrical diamidate prodrugs of nucleotide analogues for drug delivery.

The use of pronucleotides to circumvent the well-known drawbacks of nucleotide analogs has played a significant role in the area of antiviral and anticancer drug delivery. Several motifs have been designed to mask the negative charges on the phosphorus moiety of either nucleoside monophosphates or nucleoside phosphonates, in order to increase their hydrophobicity and allow entry of the compound into the cell. Among them the bis-amidate analogs, having two identical amino acids as masking groups through a P-N bond, represent a more recent approach for the delivery of nucleotide analogs, endowed with antiviral or anticancer activity. Different synthetic strategies are commonly used for preparing phosphorodiamidates of nucleosides. In this protocol, we would like to focus on the description of the synthetic methodology that in our hand gave the best results using 2'-3'-didehydro-2'-3'-dideoxythymidine (d4T, Stavudine) as model nucleoside. A second strategy for preparing diamidates of nucleoside phosphonates will be reported using {[2-(6-amino-9 H-purin-9-yl)ethoxy]methyl}phosphonic acid (PMEA, adefovir) as model substrate.

Nickel-catalyzed one-pot tandem 1,4-1,2-addition of P(O)H compounds to 1,10-phenanthrolines.

A novel and efficient nickel-catalyzed tandem 1,4-1,2-addition of P(O)H compounds to 1,10-phenanthrolines forming various 2,4-diphosphono-1,2,3,4-tetrahydro-1,10-phenanthrolines has been developed. This reaction breaks up the aromatic stabilization and directly introduces two phosphorus moieties in one single step. This finding is the first example of transition-metal-catalyzed double hydrophosphonylation of 1,10-phenanthrolines.

Straightforward synthesis towards mono and bis-phosphonic acid functionalised β-cyclodextrins

For the first time a novel class of cyclodextrins bearing phosphonic acid groups has been revealed using a new versatile methodology. These derivatives can be easily synthesised in four easy steps starting from the diol with relatively high percentage yields and no difficult purification procedures. Chemical modifications were carried out in a controlled regioselective manner using a DIBAL promoted de-O-benzylation, followed by a modified Horner–Wadsworth–Emmons reaction to introduce the key phosphorus moieties. Fully deprotected products could have wide applications as useful tools in biological systems as well as key building blocks in complex cyclodextrin chemistry.

Facile synthesis of new thermally stable and organosoluble polyamide-imides based on non-coplaner phosphorus and silicon containing amines

Two new kinds of diamines, 3-[bis-(3-aminophenyl)-phosphinoyl)-phenyl]-3-(triphenyl-phosphoranylidene)-pyrrolidene-2,5-dione, (DAP) with phosphorus moiety and bis-(5-amino-naphthalene-1-yl) dimethyl silane (DAS) with silicon moiety are synthesized. A series of novel aromatic polyamide-imides (PAIs) are prepared from three dicarboxylic acids and synthesized diamines. The phosphorus and silicon containing diamines and all polymers are characterized by FT-IR, NMR spectroscopic techniques and elemental analysis. The polymers obtained have good thermal stability and glass transition temperature (Tg) in the range of 254–315∘C. All these novel polyamide-imides (PAIs) contain 10% weight loss at the temperature above 506∘C and more than 59% residue at 600∘C in nitrogen atmosphere. The resulting polymeric films exhibit high optical transparency and inherent viscosity in the range of 0.68 to 0.79 dL/g. These polymers are found to be soluble in aprotic polar solvents such as NMP, DMSO, DMF and DMAc. Wide angle X-ray diffraction revealed that these polymers are predominantly amorphous in nature.

P(O)R2-directed Pd-catalyzed C-H functionalization of biaryl derivatives to synthesize chiral phosphorous ligands.

Chiral phosphorus ligands have been widely used in transition metal-catalyzed asymmetric reactions. Herein, we report a new synthesis approach of chiral biaryls containing a phosphorus moiety using P(O)R2-directed Pd-catalyzed C–H activation; the functionalized products are produced with good enantioselectivity.

Sterically Restricted Tin Phosphines, Stabilized by Weak Intramolecular Donor–Acceptor Interactions

Four related sterically restricted pen-substituted acenaphthenes have been prepared containing mixed tin phosphorus moieties in the proximal 5,6-positions (Acenap[SnR3][(PPr2)-Pr-i]; Acenap = acenaphthene-5,6-diyl; R-3 = Ph-3 (1), Ph2Cl (2), Me2Cl (3), Bu2Cl (4)). The degree of intramolecular P-Sn bonding within the series was investigated by X-ray crystallography, solution and solid-state NMR spectroscopy, and density functional theory (DFT/B3LYP/SBKJC/PCM) calculations. All members of the series adopt a conformation such that the phosphorus lone pair is located directly opposite the tin center, promoting an intramolecular donor acceptor P -> Sn type interaction. The extent of covalent bonding between Sn and P is found to be much greater in triorganotin chlorides 2-4 in comparison with the triphenyl derivative 1. Coordination of a highly electronegative chlorine atom naturally increases the Lewis acidity of the tin center, enhancing the Ip(P)-sigma*(Sn-Y) donor acceptor 3c-4e type interaction, as indicated by conspicuously short Sn-P peri distances and significant (1)J(P-31,Sn-119) spin spin coupling constants (SSCCs) in the range 740-754 Hz. Evidence supporting the presence of this interaction was also found in solid-state NMR spectra of some of the compounds which exhibit an indirect spin spin coupling on the same order of magnitude as observed in solution. DFT calculations confirm the increased covalent bonding between P and Sn in 2-4, with notable WBIs of ca. 0.35 obtained, in comparison to 0.1 in 1.

Asymmetric hydroformylation catalyzed by RhH(CO)₂[(R,S)-Yanphos]: mechanism and origin of enantioselectivity.

Asymmetric hydroformylation (AHF) catalyzed by transition metal (TM) complexes bearing chiral phosphorus ligands is one of the most powerful synthetic ways that could provide chiral aldehydes directly from alkenes and syngas in one step. Experiments have proved the efficiency of Rh catalyst with hybrid phosphorus ligands owning two different phosphorus moieties in AHF. Herein the origin of enantioselectivity of AHF catalyzed by RhH(CO)2[(R,S)-Yanphos] was studied at M06/BSI level using the density functional theory (DFT) method to unveil a fundamental understanding on factors contributing to the efficiency in AHF. The alkene insertion step is supposed to be the chirality-determining step in the whole catalytic cycle of the Rh-Yanphos system. Four possible pathways of styrene (Sub1) insertion step (pathways R1, S1, R2, and S2) were discussed; the calculated results indicate that pathways R1 and S2 are proposed to be two dominant alkene insertion pathways and that styrene tends to adopt apical coordination mode (A mode) to Rh center in pathways R1 and S2 compared to equatorial coordination mode (E mode) in pathways R2 and S1. The enantioselectivity of AHFs of ten alkene substrates (CH2═CH-R, R═Ph, C(═O)OCH3, Ph-(p)-Me, Ph-(p)-OMe, Ph-(p)-(i)Bu, Ph-(p)-F, Ph-(p)-Cl, Ph-(o)-F, OC(═O)-Ph and O-Ph, corresponding alkenes are abbreviated as Sub1 to Sub10, respectively) were also investigated. The predicted chiralities agree well with experimental results. The present work suggests that the relative stabilities of coordination modes (A/E mode) of alkene to 2 (RhH(CO)[(R,S)-Yanphos]) might be of importance in the enantioselectivity of AHF catalyzed by Rh-Yanphos.

Analysis of glycerophospho‐ and sphingolipids by CE

Glycerophospholipids are amphiphilic molecules possessing polar head groups with a glycerol backbone and nonpolar variable long-chain fatty acids. Numerous molecular species are found in a single class of glycerophospholipid, conferring to these lipids a high structural diversity. They are major components of biological membranes and participate in important activities involving cell signaling and substrate transport. Sphingolipids consist of long-chain bases linked by an amide bond to a fatty acid and via the terminal hydroxyl group to complex carbohydrate or phosphorus moieties, constituting a complex family of compounds that also present an enormous structural variability. As important component of neuronal membranes, sphingolipids contribute to cellular diversity and functions and are associated with several neurodegenerative disorders. Moreover, they were studied in several foods due to their sensorial, reological, and antioxidant characteristics. In this work, the most relevant information available on glycerophospholipid and sphingolipid analysis by CE is reviewed. CE is a very promising analytical technique in polar lipid analysis, which provides high efficiency, relatively high resolution, and enormous versatility and requires small amounts of sample and solvent. MEKC and NACE methodologies have been developed as the most useful alternatives for these analyses by CE. Very interesting LODs have been achieved enabling the application of CE to the determination of glycerophospholipids and sphingolipids in several food and biological matrices.

Skeletally Modified Polyamide Flame Retardant Coatings

The use of polyamide coatings for electrical applications is restricted mainly because of its inadequate flame retardant behaviour. In order to improve its flame retardant behaviour, polyamide is modified by incorporating phosphorus moiety in its backbone. The structure of the phosphorus and poly amide was confirmed by infrared spectroscopy (FT-IR), NMR, thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), UL-94 vertical burning tests and char residue tests. From the results obtained, we observe that the incorporation of phosphorus into the polyamide enhances its thermal stability and flame retardancy.

Catalyst Activity and Selectivity in the Isomerising Alkoxycarbonylation of Methyl Oleate

The synthesis of unsymmetrical diphosphine ligands (3a-g) with an o-tolyl backbone and tert-butyl, adamantyl, cyclohexyl and isopropyl substituents on the phosphorus moiety is described (1,2-(CH2PR2)(PR'2)C6H4; 3a: R=tBu, R'=tBu, 3b: R=tBu, R'=Cy, 3c: R=tBu, R'=iPr, 3d: R=Ad, R'=tBu, 3e: R=Ad, R'=Cy, 3f: R=Cy, R'=Cy, 3g: R=Ad, R'=Ad). The corresponding diphosphine-Pd(II) ditriflate complexes [(P^P)Pd(OTf)2] (5a-g) were prepared and structurally characterised by X-ray crystallography. These new complexes were studied as catalyst precursors in the isomerising methoxycarbonylation of methyl oleate, and were found to convert methyl oleate into the corresponding linear α,ω-diester (L) with 70-80% selectivity. The products of this catalytic reaction with the known [{1,2-(tBu2PCH2)2C6H4}Pd(OTf)2] complex (5h) were fully analysed, and revealed the formation of the linear α,ω-diester (L, 89.0%), the methyl-branched diester B1 (4.3%), the ethyl-branched diester B2 (1.0%), the propyl-branched diester B3 (0.6%) and all diesters from butyl- to hexadecyl-branched diesters B4-B16 (overall 4.8%) at 90 °C and 20 bar CO. The productivity of the catalytic conversion of methyl oleate with complexes 5a-g varied with the steric bulk of the alkyl substituent on the phosphorus. Ligands with more bulky groups, like tert-butyl or adamantyl (e.g., 5a, 5d, 5g), were more productive systems. The formation of the catalytically active hydride species [(P^P)Pd(H)(MeOH)](+) (6-MeOH) was investigated and observed directly for complexes 5a-e and 5g, respectively. These hydride species were isolated as the corresponding triphenylphosphine complexes (6-PPh3) and fully characterised, including by X-ray crystallography. The catalytic productivity of 6a-PPh3 was virtually identical to that of 5a, thereby confirming the efficient hydride formation of 5a under catalytic conditions.

ChemInform Abstract: When Phosphorus and NHC (N‐Heterocyclic Carbene) Meet Each Other

AbstractReview: 138 refs.

Chemoselective deoxygenation of 4,5-dinitroacenaphthenequinone with hexaethyltriamidophosphite

Deoxygenation under the action of the P(III) derivatives is widely used in organic chemistry [1, 2]. Among the variety of reactions a separate group includes the deoxygenation of nitro compounds with the P(III) derivatives resulting in the nitrogencontaining heterocycles of different structures [3]. The tertiary phosphines and phosphites are most commonly used as the P(III) derivatives. One of the most studied reactions of this type is the cyclization of nitroarenes to form the corresponding nitrogen-containing heterocycles (indoles, pyrrolopyrimidines, carbazoles, quinolines) under the action of the phosphorous acid esters. Presumably, the reaction proceeds through the intermediate formation of nitrenes. If 2-nitrobiaryls were used, the nitrene inserts on the C–H bond adjacent to the aryl moiety, to give the corresponding carbazoles [4, 5] or δ-carbolines [6]. The reaction of 2nitrophenylsulfide with an excess of triethyl phosphite, resulting in phenothiazine, can be attributed to the same type of the reactions [7, 8]. If the aryl contains a double bond ortho-positioned relative to the nitro group (o-nitrostyrene), the nitrene inserts on the β-C– H bond of the vinyl moiety to give the substituted indoles [9–11]. The reactions of o-dinitrobenzene with the P(III) derivatives should be specially noted. For example, under the action of triethyl phosphite, diphenylethylphosphinite, or methyldiethylphosphonite one of the nitro groups is substituted by the phosphorus moiety and ethyl nitrite is eliminated [12]. At the same time, the reduction of 2,2'-dinitrobiphenyl with the gaseous PH3 stops when benzocinnoline-2,2'dioxide forms [13].

When phosphorus and NHC (N-heterocyclic carbene) meet each other

Since the discovery of the first air stable NHC, this class of compounds has been intensively studied and applied in organometallic chemistry and homogeneous catalysis due to the stability brought to the metal centre. Alternatively, phosphorus based family ligands have already a very long history in these fields of chemistry. It was naturally obvious that the NHC and the phosphorus ligands had to be mixed for the best of organometallic chemistry and homogeneous catalysis. This perspective will highlight the new synthetic routes for NHC bearing a phosphorus moiety such as NHC-phosphenium salt, N-phosphorylated-imidazolium salt, 4-phosphino or 4,5-diphosphino-imidazolium salt and tethered phosphino-imidazolium salt. Then, the recent applications in organometallic chemistry and homogeneous catalysis will be presented.

FLAME RETARDATION PERFORMANCES OF HALOGEN-FREE FLAME RETARDANT WHEN APPLIED TO UNSATURATED POLYESTER

In order to improve fire performance of polymeric materials, phosphorus flame retardants (FRs) were studied in an attempt to obtain UL-94 ratings for materials based on unsaturated polyester. The fire behaviors and thermal stability properties were evaluated using UL-94 vertical test and thermogravimetric analysis (TGA). The UL-94 test results show that V-1 rating is achieved. TGA and UL-94 results concluded that phosphorus FRs employed in this study works on both vapor phase and condensed phase, but the vapour phase is dominant mode of action. These suggested that the addition of FRs probably does affect on the char layer formed during combustion behavior and increase the flame retardant properties in the case of condensed phase mode of action. The efficiency of flame retardant of phosphorus also highly depends upon the phosphorus moieties generated during the decomposition which further converted to radical capturing species, and consequently quenching the flame in the case of gas phase mode of action. These FRs can be promising candidates that replace the halogen-based.

Why calcium inhibits magnesium-dependent enzyme phosphoserine phosphatase? A theoretical study

Phosphoserine phosphatase (PSP) utilizes one Mg2+ ion to catalyze the hydrolysis of phospho-l-serine. The displacement of Mg2+ by Ca2+ results in the loss of activity. The reaction mechanisms for the enzyme with both Mg2+ and Ca2+ bound were investigated using hybrid density functional theory. A large quantum chemical model abstracted from the X-ray crystal structure was employed in the calculations. Our calculations shed new insight into the catalytic mechanism of the natural enzyme and its lack of activity by Ca2+ substitution. For the catalytic reaction, our calculations showed that the whole reaction proceeds through two steps, namely dephosphorylation and phosphate hydrolysis. The associated barriers for these two steps are calculated to be 11.9 and 12.0 kcal mol−1, respectively. The Mg-bound Asp11 residue functions as a nucleophile to attack the phosphorus moiety, in concomitant with the departure of the leaving group, which takes a proton from the neutral Asp13 residue. In the subsequent step, the newly formed anionic Asp13 residue activates a water molecule to perform the reverse attack on the phosphoryl intermediate, affording the phosphate product. The substitution of Mg2+ by Ca2+ results in different metal coordination fashion, in which the Asp167 residue changes from bidentate to monodentate and a second water molecule becomes ligated to Ca2+. The calculated barriers for the hydrolysis are ca 8 kcal mol−1 higher than those in the native enzyme, which reconciles with the fact that Ca2+ inhibits the activity of PSP. Several possible reasons are discussed.

On the Intramolecular Interactions of Si/P in 1,2-Phenylene Frameworks

The synthesis and structure of 1-diphenylphosphino-2-(fluorodiphenylsilyl) benzene 1 and 1-diphenylphosphino-2-(difluorophenylsilyl)- benzene 2 are reported. An X-ray crystal structure analysis of 1 shows a weak interaction between the silicon and phosphorus moieties, producing a hypervalent state at the silicon. The hypervalent state of the silicon is also supported by a natural bond orbital calculation. However, despite having a difluorosilyl group, 2 does not show a hypervalent state for the silicon, based on an X-ray crystal structure analysis. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 00:1–5, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21044

Flame retardant polymeric materials achieved by incorporation of styrene monomers containing both nitrogen and phosphorus

Organophosphorus compounds have a long history as effective flame retardants for polymeric materials. There is increasing interest in developing new phosphorus flame retardants as a consequence of the increasing worldwide regulatory pressure on the use of organohalogen flame retardants which are persistant in the environment, tend to bioaccumulate, and pose potential health risks for the human population. It has been widely suggested that the flame retardant activity of phosphorus compounds may be enhanced by the presence of nitrogen, sulfur, silicon and a few other elements. This has been tested by examining the flamability behavior of copolymers derived from styrene monomers containing phosphorus moieties in comparison to those containing similar monomers in which both phosphorus and nitrogen are present.