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[reaction: see text]. Addition of dialkyl disulfides to terminal alkynes is catalyzed by a rhodium-phosphine complex and trifluoromethanesulfonic acid giving (Z)-bis(alkylthio)olefins stereoselectively.
Various experimental techniques are available for the investigation of dynamic surface tension, and a generally accepted theoretical model of these dynamics has been established. However, reliable rheological parameters of a fluid surface are very scarce. Therefore, comparisons of rheological parameters resulting from slow and faster processes or from theoretical calculations are required. In particular, a comprehensive experimental verification of the complex surface elasticity modulus which characterizes the dynamic behavior of a fluid surface in an appropriate manner is desirable. For this reason a new version of oscillating bubble method was developed which allows exact measurements of the complex elasticity modulus in the frequency range 3-500 Hz. With this method the assumptions of the theory of dynamic surface tension can be verified for medium frequencies. The new experimental results, in particular the experimental determination of the Gibbs elasticity, reveal that these assumptions are only approximately valid for faster processes. However, with a slight modification of the established model the experimental results can be explained. These experiments were carried out with solutions of tridecyl dimethyl phosphine oxide, fatty acids, n-alkanols, and triton X-100 at different surfactant concentrations. Copyright 1998 Academic Press.
[reaction: see text] The reaction of several phosphines with an acidic indicator gives both ion pairs and free ions. The value obtained for the pKa of tribenzylphosphine is shown to be reasonable by MO computations. An important limitation is demonstrated for the Fuoss equation of dissociation of ion pairs.
[reaction: see text] In an effort to develop a more concise route to differentially substituted pyrroles (such as that found in the lamellarins), a completely regioselective one-pot double Suzuki coupling has been discovered. The key feature is the use of a ligand-free palladium catalyst under optimized conditions, which results only in coupling of the C5 bromide. At this point, addition of a second boronic acid and a phosphine ligand enables coupling at the remaining C4 bromide.
Dimethyl hydrogen phosphite (DMHP) is used as an intermediate in the production of insecticides and herbicides, as an additive to lubricants, and as a stabilizer in oil and plaster and was considered for use as a chemical to simulate the physical (but not the biologic) properties of anticholinesterase agents. Results of 13-week gavage studies in F344/N rats (0-400 mg DMHP/kg body weight) and in B6C3F1 mice (0-1,500 mg DMHP/kg body weight) were used to identify short-term toxicity and to establish doses for the 2-year toxicology and carcinogenesis studies. In these studies, dimethyl hydrogen phosphite (greater than 97% pure) was administered for 103 weeks in corn oil by gavage to groups of 50 male F344/N rats and to groups of 50 male and female B6C3F1 mice at doses of 0, 100, or 200 mg/kg and to groups of 50 female F344/N rats at doses of 0, 50, or 100 mg/kg. In the 2-year studies, survival of high dose male rats and high dose male mice was lower (P<0.05) than that of the vehicle controls (male rats: vehicle control, 39/50; low dose, 29/50; high dose, 23/50; male mice: 42/50; 34/50; 32/50). At the end of the studies, mean body weights were lower than those of the corresponding vehicle controls for high dose male rats (-15%), for high dose female rats (-5%), and for high dose male mice (-5%). Dimethyl hydrogen phosphite caused dose-related increases in nonneoplastic and neoplastic lesions of the lung in male and female rats. In high dose male rats, there were increased incidences of lung neoplasms, including squamous cell carcinomas (0/50; 0/50; 5/50), alveolar/bronchiolar adenomas (0/50; 0/50; 5/50), and alveolar/bronchiolar carcinomas (0/50; 1/50; 20/50). In high dose female rats, there was a marginal increase in the incidence of alveolar/bronchiolar carcinomas of the lung (0/50; 1/49; 3/50). Hyperplasia of the lung and chronic interstitial pneumonia were increased in dosed male rats and in high dose female rats. Dimethyl hydrogen phosphite caused increases in forestomach lesions in male and female rats. In male rats, there was an increased incidence of forestomach neoplasms, including squamous cell papillomas (0/50; 1/50; 3/50) and squamous cell carcinomas (0/50; 0/50; 3/50). High dose male rats had increased incidences of hyperkeratosis and hyperplasia of the forestomach. In high dose female rats, the incidence of forestomach hyperplasia was increased. Neoplastic lesions of the forestomach (a squamous cell papilloma and a squamous cell carcinoma) were found in two high dose female rats. Mineralization of the cerebellum was seen in high dose male rats (12/49) and in no other group. Focal calcification of the testis occurred at increased incidence in dosed male mice in the 2-year studies (2/50; 9/47; 24/50). Compound-related testicular atrophy was seen in male mice in the 13-week study. Dimethyl hydrogen phosphite did not induce any neoplasms in male or female mice. Dimethyl hydrogen phosphite was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat or Syrian hamster liver S9. This chemical did not induce sex-linked recessive lethal mutations in Drosophila melanogaster. An audit of the experimental data was conducted for these carcinogenic studies on dimethyl hydrogen phosphite. No data discrepancies were found that influenced the final interpretations. Under the conditions of these gavage studies, there was clear evidence of carcinogenicity in male rats receiving dimethyl hydrogen phosphite, as shown by increased incidences of alveolar/bronchiolar adenomas, alveolar/bronchiolar carcinomas, and squamous cell carcinomas of the lung and of neoplasms of the forestomach. There was equivocal evidence of carcinogenicity in female F344/N rats receiving dimethyl hydrogen phosphite, as shown by marginally increased incidences of alveolar/bronchiolar carcinomas of the lung and of neoplasms of the stomach. There was no evidence of carcinogenicity in male or female B6C3F1 mice receiving dimethyl hydrogen phosphite at doses of 100 ogen phosphite at doses of 100 or 200 mg/kg for 103 weeks. Synonyms: phosphonic acid, dimethyl ester (9CI); dimethyl phosphite; dimethyl phosphorus acid; methyl phosphonate; dimethyl phosphonate; dimethoxyphosphine oxide; TL 585; DMHP; phosphorous acid, dimethyl ester; dimethylphosphite; dimethyl phosphonate; dimethylphosphorous acid; bis(hydroxymethyl) phosphine oxide
Mixed carboxylic-phosphinic anhydrides derived from peptide acids and 1-oxo-1-chlorophospholane have been applied in the synthesis of the protected [Leu11]-SP by the fragment coupling strategy. The yields from fragment couplings were ca. 75%, the products were of high purity while the conditions of formation and coupling of the corresponding mixed phosphinic anhydrides, for optimum yields, have been evaluated.
There is still a lot of controversy in literature concerning the question whether a biochemical system exists enabling micro-organisms to reduce phosphate to phosphine gas. The search for so-called 'de novo synthesised' phosphine is complicated by the fact that soils, slurries, sludges, etc., which are often used as inocula, usually contain matrix bound phosphine (MBP). Matrix bound phosphine is a general term used to indicate non-gaseous reduced phosphorus compounds that are transformed into phosphine gas upon reaction with bases or acids. A study was carried out to compare the different digestion methods, used to transform matrix bound phosphine into phosphine gas. It was demonstrated that caustic and acidic digestion methods should be used to measure the matrix bound phosphine of the inoculum prior to inoculation to avoid false positive results concerning de novo synthesis. This is especially true if anthropogenically influenced inocula possibly containing minute steel or aluminium particles are used. The comparative study on different digestion methods also revealed that the fraction of phosphorus in mild steel, converted to phosphine during acid corrosion depended on the temperature. Following these preliminary studies, anaerobic growth experiments were set up using different inocula and media to study the emission of phosphine gas. Phosphine was detected in the headspace gases and its quantity and timeframe of emission depended on the medium composition, suggesting microbially mediated formation of the gas. The amount of phosphine emitted during the growth experiments never exceeded the bound phosphine present in inocula, prior to inoculation. Hence, de novo synthesis of phosphine from phosphate could not be demonstrated. Yet, microbially mediated conversion to phosphine of hitherto unknown reduced phosphorus compounds in the inoculum was evidenced.
A new approach for simultaneous analysis of biologically active aminoalkanephosphonic acids, namely glyphosate, phosphonoglycine, phosphonosarcosine, phosphonoalanine, phosphono-beta-alanine, phosphonohomoalanine, phosphono-gamma-homoalanine and glufosinate, is presented. This includes a preliminary 31p NMR analysis of these amino acids, their further derivatization to volatile phosphonates (phosphinates) by means of trifluoroacetic acid-trifluoroacetic anhydride-trimethyl orthoacetate reagent and subsequent analysis of derivatization products using MS and/or GC-MS (chemical ionization and/or electron impact ionization).
Solid-phase synthesis of phosphinic peptides was introduced 10 years ago. A major application of this chemistry has been the development of potent synthetic inhibitors of zinc metalloproteases. Specific properties of the inhibitors produced in recent years are reviewed, supporting the notion that phosphinic pseudo-peptides are useful tools for studying the structural and functional biology of zinc proteases.
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A three-component condensation reaction of Fmoc-carbamate, aldehydes, and alkylphosphinic acids provides a new, direct, and efficient method for synthesizing Fmoc-protected phosphinic pseudodipeptidic blocks, directly usable for solid-phase peptide synthesis. [reaction: see text]
A series of N-protected beta-amino phosphonic acid esters have been prepared by phosphine-catalyzed allylic substitution of 2-(diethylphosphonyl)-substituted allylic acetates employing 4,5-dichlorophthalimide as nucleophilic partner. These organocatalytic allylic substitutions exhibit exceptionally high levels of regiospecificity by virtue of a tandem S(N)2'-S(N)2' mechanism.
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[reaction: see text] Glyoxal bis(N-methyl-N-phenylhydrazone) (1) and its related compounds such as 2-pyridinecarboxaldehyde N-methyl-N-phenylhydrazone (3) were prepared and examined as ligands for the Suzuki-Miyaura cross-coupling reaction of aryl halides and arylboronic acids. We found phosphine-free catalysts, such as Pd(OAc)(2)/hydrazone ligand 1 or 3, to be efficient catalysts for a variety of substrates to produce the coupling products in good yields.
Bis(hydroxy)phosphine, the isomer of hypophosphorous acid which remained elusive for a long time, coordinates to the Ni site of heterometallic clusters with a W3NiQ4 core (Q = S, Se) to give [W3(Ni(HP(OH)2))Q4(H2O)9]4+ (Q = S, Se).
Six secondary phosphine oxides and their tautomeric equilibria as free ligands and in the presence of an equimolar amount of the chiral dirhodium complex Rh* are described and discussed. Discrimination of enantiomers is easily possible by inspecting the (31)P NMR resonances; some (1)H and (13)C NMR resonances are useful as well. H/D exchange of the acidic protons in the phosphine oxides takes place with acetone-d(6), the solvent additive, after some hours but does not obscure the chiral recognition experiment. (103)Rh,(31)P coupling constants are discussed briefly. Decomposition of ligand molecules in 1:1-Rh*-adducts occurs slowly but completely.
The solvent extraction of chromium(VI) in chloroform, dichloromethane, dichloroethane and its transport through a chloroformic bulk liquid membrane from sulphuric acid solutions with the neutral extractant triphenylphosphine (TPP) were studied. It was highlighted that the TPP extractant is an interesting complexing and efficient carrier for transport of chromium(VI) as [(HTPP)HCr2O7] complex from a 2M sulphuric acid solutions. It has a high ability to concentrate the chromium(VI) in the receiving phase according to the Donnan equilibrium. The co-extraction and the co-transport of sulphuric acid is very low and has no effect on the transport efficiency. The transport rate depends mainly on the initial concentration of the extractant.
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