Synthesis of Tpiaryl Phosphates Catalysed by Polyethylene Glycols in a Two-Phase System: Phase Transfer Catalysis

The synthesis of triaryl phosphates has been accomplished, at room temperature, in nearly quantitative, yields in a two-phase system with poly(ethylene glycol) as a phase transfer catalyst.     

Thermal and spectroscopic characterization of a triaryl phosphate hydraulic fluid

The thermal stability of a commercial triaryl phosphate hydraulic fluid has been assessed using thermogravimetry and pyrolysis. This material is a mixture of triaryl phosphates containing a predominance of triphenyl phosphate. It is volatile at higher temperatures. At temperatures below its boiling point, in the presence of air, it slowly decomposes to evolve phenolic fragments.     

Polymer Supported Reagents: An Efficient and Simple Method for the Synthesis of Triaryl Phosphates

The reaction of phosphoryl chloride with insoluble polymer-supported phenoxide ion reagents in benzene at room temperature, produced triaryl phosphates in excellent yields. The isolation of pure products by simple filtration and evaporation is an important feature of this method.     

Cooperative Activation with Chiral Nucleophilic Catalysts and N‐Haloimides: Enantioselective Iodolactonization of 4‐Arylmethyl‐4‐pentenoic Acids

Chiral triaryl phosphates promote the enantioselective iodolactonization of 4‐substituted 4‐pentenoic acids to give the corresponding iodolactones in high yields with high enantioselectivity. N‐Chlorophthalimide (NCP) is employed as a Lewis acidic activator and oxidant of I₂ for the present iodolactonization. In combination with 1.5 equivalents of NCP, only 0.5 equivalents of I₂ are sufficient to generate the iodinating reagent.     

Determination of Trialkyl and Triaryl Phosphates by Narrow-bore Liquid Chromatography with On-line Thermionic Detection

Abstract

The potential of a previously reported on-line reversed-phase liquid chromatography-thermionic detector (LC–TID) system has been further evaluated. Several trialkyl (trimethyl to tri-octyl) and triaryl (triphenyl and tri-o-cresyl) phosphates were chosen as model compounds. LC was done on an alkyl-bonded silica column with methanol-water (80:20) at a flow-rate of 35—70μ/min as eluent. The band broadening in the interface-TID unit increased with decreasing volatility of the compounds and for the relatively non-volatile compounds, the band broadening decreased with increasing eluent flow-rate.

For most of the test compounds, detection limits of 40–100pg were obtained. As an illustration of the high selectivity of the LC[sbnd]TID system, the trace-level determination of two aryl phosphates in sediment samples is reported.     

Determination of airborne trialkyl and triaryl organophosphates originating from hydraulic fluids by gas chromatography-mass spectrometry. Development of methodology for combined aerosol and vapor sampling

Methodology for personal occupational exposure assessment of airborne trialkyl and triaryl organophosphates originating from hydraulic fluids by active combined aerosol and vapor sampling at 1.5L/min is presented. Determination of the organophosphates was performed by gas chromatography-mass spectrometry. Combinations of adsorbents (Anasorb 747, Anasorb CSC, Chromosorb 106, XAD-2 and silica gel) with an upstream cassette with glass fiber or PTFE filters and different desorption/extraction solvents (CS(2), CS(2)-dimethylformamide (50:1, v/v), toluene, dichloromethane, methyl-t-butyl ether and methanol) have been evaluated for optimized combined vapor and aerosol air sampling of the organophosphates tri-isobutyl, tri-n-butyl, triphenyl, tri-o-cresyl, tri-m-cresyl and tri-p-cresyl phosphates. The combination of Chromosorb 106 and 37 mm filter cassette with glass fiber filter and dichloromethane as desorption/extraction solvent was the best combination for mixed phase air sampling of the organophosphates originating from hydraulic fluids. The triaryl phosphates were recovered solely from the filter, while the trialkyl phosphates were recovered from both the filter and the adsorbent. The total sampling efficiency on the combined sampler was in the range 92-101% for the studied organophosphates based on spiking experiments followed by pulling air through the sampler. Recoveries after 28 days storage were 98-102% and 99-101% when stored at 5 and -20 degrees C, respectively. The methodology was further evaluated in an exposure chamber with generated oil aerosol atmospheres with both synthetic and mineral base oils with added organophosphates in various concentrations, yielding total sampling efficiencies in close comparison to the spiking experiments. The applicability of the method was demonstrated by exposure measurements in a mechanical workshop where system suitability tests are performed on different aircraft components in a test bench, displaying tricresyl phosphate air concentrations of 0.024 and 0.28 mg/m(3), as well as during aircraft maintenance displaying tri-n-butyl phosphate air concentrations of 0.061 and 0.072 mg/m(3).     

Synthesis of 4‐(Isothiazol‐3‐yl)morpholines and 1‐(Isothiazol‐3‐yl)piperazines,and Their Inhibitory Activity towards Acetylcholinesterase

The synthesis of novel triaryl‐substituted 4‐(isothiazol‐3‐yl)morpholines 7 and 8 , and 1‐(isothiazol‐3‐yl)piperazines 9 – 13 by reaction of the corresponding isothiazolium salts 5 and 6 with secondary amines in the presence of t‐BuOK in absolute THF is described. Some representatives of the isothiazoles were evaluated as inhibitors of acetylcholinesterase from Electrophorus electricus.     

Inducing Propeller Chirality in Triaryl Boranes with Chiral Amines

Stabilization of chiral propeller conformations in triaryl compounds is challenging due to generally low racemization barriers. Nonetheless, it was recently found that chiral conformational preferences can be induced to triaryl boranes by incorporating point-chiral alkylether chains to the aryl blades and subsequently locking the structure with ammonia. A four-point interaction, meaning that the cooperative effects of Lewis-adduct formation and three hydrogen bonds, was proposed as stabilizing mechanism. Herein, it was shown that three such strong interactions suffice to introduce a preferential propeller handedness. Although DFT calculations predict no noteworthy preferences for either P- or M-chiral propellers for some of the investigated triarylborane–amine adducts that were prepared with chiral primary amines, vibrational circular dichroism (VCD) spectroscopic characterizations revealed that there is indeed a measurable excess of one propeller handedness. Furthermore, the steric demand of the amine was found to play a key role in the induction process and especially in preventing blade rotations.     

Sequential asymmetric homoallenylation of primary amines with a palladium catalyst

Optically active bis(homoallenyl)amines bearing two chiral axes with the same sense of axial chirality were prepared by a one-pot, palladium-catalyzed sequential homoallenylation of primary amines with 2,3-allenyl phosphates.     

Selective deoxygenation of aryl selenoxides by triaryl phosphites. Evidence for a concerted transformation

Triaryl phosphites selectively reduce aryl selenoxides to selenides. The Hammett plot of the reactions of para-phenyl substituted triaryl phosphites with diphenyl selenoxide gave ρ=+2.3, whereas with bis(p-methoxyphenyl) selenoxide, ρ=−2.1. The results are consistent with a concerted mechanism for the oxygen transfer from Se to P.     

Nickel-catalyzed cross-coupling of aryl phosphates with arylboronic acids

The Suzuki-Miyaura cross-coupling of aryl phosphates using Ni(PCy(3))(2)Cl(2) as an inexpensive, bench-stable catalyst is described. Broad substrate scope and high efficiency are demonstrated by the syntheses of more than 40 biaryls and by constructing complex organic molecules. The poor reactivity of aryl phosphates relative to aryl halides is successfully employed to construct polyarenes by selective cross-coupling using Pd and Ni catalysts.     

Adamantane-like aluminum amide-phosphate from alumazene

A dealkylsilylation reaction between alumazene [2,6-(i-Pr)(2)C(6)H(3)NAlMe](3) (1) and tris(trimethylsilyl) ester of phosphoric acid (2) in a 1:3 molar ratio provides the heteroadamantane molecule (MeAl)[2,6-(i-Pr)(2)C(6)H(3)N](3)[Al[OP(OSiMe(3))(3)]](2)(O(3)POSiMe(3)) (3). Compound 3 was characterized by analytical and spectroscopic methods, and its molecular structure was established by a single-crystal X-ray diffraction experiment. Moreover, trialkyl and triaryl phosphates and dialkyl phosphonates react with 1 at elevated temperature to afford an intractable mixture of products. The reaction of phosphonic acids with 1 proceeds under decomposition to yield 2,6-diisopropylaniline and aluminophosphonates.     

The Reactivity of Mn(II) and Ti(IV) Dialkylamides with Organophosphorus Esters

Abstract

Treatment of dialkyl (or diaryl) phosphites with titanium tetrakis-(diethylamide) at room temperature resulted in a smooth displacement of both ester functions by the diethylamino groups to give bis(diethylamino) phosphorus acid (58–65%). The same results are obtained at ?40° and no evidence of an intermediate product was detected using ¹H n.m.r. techniques. Treatment of dimethyl phosphite with titanium tetrakis(n-dibutylamide) resulted in isolation of two products which were identified as bis-(n-dibylamino) phosphorus acid (52%) and methyl-(n-dibutylamino) phosphorus acid (21%). On the other hand, trialkyl (triaryl) phosphates are inert to the titanium reagents.     

Nickel-catalyzed amination of aryl tosylates

The cross-coupling of aryl tosylates with amines and anilines was accomplished by using a Ni-based catalyst system from the combination of Ni(II)-(sigma-aryl) complexes/N-heterocyclic carbenes (NHCs). The feature, scope, and limitation of this reaction are disclosed.     

Syntheses of phenanthridines and benzophenanthridines by intramolecular ortho-arylation of aryl amide ions with aryl halides via SRN1 reactions

The photostimulated reaction of N-(2-halo-benzyl)aryl amines with t-BuOK in liquid ammonia affords fused azaheterocycles by the S_RN1 mechanism. The starting materials are easily obtained by the reaction of 2-halo-benzyl chloride and aromatic amines to prepare the secondary amines. Through this approach, phenanthridine (90%), 4-phenylphenanthridine (87%), benzo[a]phenanthridine (98%), and benzo[c]phenanthridine (84%) were synthesized.     

Unexpected regioselectivity in the palladium‐catalyzed reaction of silacyclobutanes with aryl iodides

The reaction of aryl iodides with 1,1‐diphenyl‐silacyclobutane in the presence of a catalytic amount of Pd(PPh₃)₄ affords unexpected ring‐opening adducts, 1‐ and 2‐propenyl(triaryl)‐silanes, in good yields. On the other hand, the PdCl₂(PhCN)₂‐catalyzed reaction of 1,1‐diphenylsilacyclobutanes with aryl halides gives ­unexpected products, triarylsilanols, after ­hydrolysis in moderate yields. The catalysis involves the reaction of aryl–palladium intermediates with silacyclobutanes along with ­regioselective aryl–silicon bond formation. Copyright © 2001 John Wiley & Sons, Ltd.     

Palladium(O)-catalyzed allylic alkylation and amination of allylic phosphates

Allyl diethyl phosphates (1) can be easily substituted with malonates and amines in the presence of palladium(O) catalyst. Synthetic utility of the reaction is demonstrated by the sequential amination-amination and alkylation-amination of (Z)-4-acetoxybut-2-enyl diethyl phosphate (1b) with high regio- and stereoselectivity.     

New condensing reagents for stereospecific synthesis of dinucleoside monophosphate aryl esters

Condensation of 5′-O-dimethoxytritylnucleoside 3′-O-(o-chlorophenyl) phosphates and 3′-O-benzoylnucleosides with a new condensing reagent, 2,4,6-triisopropylbenzenesulfonyl 5-(pyridin-2-yl) tetrazolide gave o-chlorophenyl ester of protected dinucleoside monophosphates which had a stereospecific configuration. The corresponding mesitylenesulfonyl derivative gave similar results.     

Efficient nickel-mediated intramolecular amination of aryl chlorides

The use of an in situ generated Ni(0) catalyst associated with 2,2'-bipyridine or N,N'-bis(2,6-diisopropylphenyl)dihydroimidazol-2-ylidene (SIPr) as a ligand and NaO-t-Bu as the base for the intramolecular coupling of aryl chlorides with amines is described. The procedure has been applied to the formation of five-, six-, and seven-membered rings. [reaction: see text]     

Iron-phosphine, -phosphite, -arsine, and -carbene catalysts for the coupling of primary and secondary alkyl halides with aryl Grignard reagents

Simple catalysts formed in situ from iron chloride and a wide range of monodentate and bidentate phosphines and arsines have been screened in the coupling of alkyl halides bearing beta-hydrogens with aryl Grignard reagents. The best of these show excellent activity, as do catalysts formed in situ with monodentate trialkyl and triaryl phosphite ligands. N-heterocyclic carbene-based precatalysts, either preformed or made in situ, also show excellent performance.