Triethyl Phosphite Research Articles

Stereospecific Deoxygenation of Phosphine Oxides with Retention of Configuration Using Triphenylphosphine or Triethyl Phosphite as an Oxygen Acceptor

[reaction: see text] A new protocol for deoxygenation of various phosphine oxides with retention of configuration is described. The advantage of the new method includes milder conditions and considerably shortened reaction times. Mechanistic studies about the oxygen transfer between the starting phosphine oxide and the sacrificial triphenylphosphine are also presented.

Preparation of silver thin films using liquid-phase precursors by metal organic chemical vapor deposition and their conversion to silver selenide films by selenium vapor deposition

A series of new Ag precursors containing β-diketonate and neutral phosphite ligands were synthesized and characterized by various spectroscopic methods. These volatile precursors in liquid phase were thermally stable and quite useful in the preparation of silver thin films through bubbler-type chemical vapor deposition (CVD). In a typical case of silver (I) 1,1,1-trifluoro-2,4-pentanedionate triethyl phosphite adduct ((tfac)AgP(OEt)3) precursor, very pure silver thin films were obtained under relatively mild conditions without any appreciable amount of F, O, and P impurities. These thin films were easily converted to β-orthorhombic silver selenide by simple selenium vapor deposition method. In scanning electron microscopic analyses, the average particle size of the latter was found to increase to about 1.26 μm after gas-phase selenization reaction.

Reactions of N-aroxycarbonyltrichloroacetimidates with nucleophilic phosphorus derivatives

Aryl N-aroxycarbonyltrichloroacetimidates (Ar = Ph, 4-FC6H4) react with diphenylphosphinite according to the scheme of the aza-Perkow reaction to give the corresponding aryl N-(1-aroxy-2,2-dichloro-vinyl)-N-diphenylphosphinoylcarbamates. The structure of one of these compounds was confirmed by single crystal X-ray diffraction analysis. In the case of electron-accepting substituents (Ar = 4-O2N6H4), the primary product undergoes mild β-elimination to give nitrophenyl diphenylphosphinate and 1-nitrophenoxy-2,2-dichlorovinyl isocyanate. The reaction of trichloroacetimidates with triethyl phosphite yields a mixture of O- and N-phosphorylation products.

Mild and High-Yielding Syntheses of Diethyl Phosphoramidate-Stoppered [2]Rotaxanes

The mild and efficient reaction between triethyl phosphite and benzylic azides allows us not only to construct rotaxanes in high yield from dibenzo[24]crown-8 (DB24C8) and dibenzylammonium (DBA(+))-derived threads but also to incorporate di(p-toluidine)[24]crown-8, which binds DBA(+) ions much more weakly than does DB24C8, into a corresponding [2]rotaxane.

Synthesis of mono- and disaccharide analogs of moenomycin and lipid II for inhibition of transglycosylase activity of penicillin-binding protein 1b

Three types of mono- and disaccharides 3a, b, 4a– c, 5, and some chaetomellic acid A analogs 6 and 42– 44 were synthesized as potential inhibitors of the transglycosylase activity of penicillin-binding protein 1b (PBP1b), a key bacterial enzyme responsible for the formation of the polysaccharide backbone of peptidoglycan as well as for cross-linking of its peptide portions. The target compounds combine structural features of both the active portion of moenomycin and the natural PBP1b substrate, lipid II. The desired skeletons were obtained in a convergent fashion involving attachment of the lipid-alkylated glyceric acid moieties 11a, b to the corresponding carbohydrate-containing phosphonic acids 23, 24a, and 24b. Compounds 3a, b were prepared to verify the distance requirements between the sugar and the noncleavable C-phosphonate moieties. Compounds 4a– c were synthesized to examine the importance of the first sugar unit of moenomycin, a known inhibitor of transglycosylase catalysis by PBP1b, with respect to antibiotic activity. These were prepared by condensation of 11a, b with 28a and 28c, which were made by glycosylation of 3-bromopropanol with oxazolines 25a, b, and Arbuzov reaction with triethyl or trimethyl phosphite, followed by dealkylation with bromotrimethylsilane. Compound 5 was generated to verify the possibility of using a dicarboxylate group to mimic the diphosphate of lipid II. It was synthesized by coupling of alcohol 31 with α-trichloroacetimidate 34. Chaetomellic acid A analogs were prepared by a Michael addition to dimethyl acetylenedicarboxylate. With the exception of 3b, all of the target compounds were found to inhibit PBP1b, albeit with modest potency.

Sol–Gel Preparation and Properties of Fluoride‐Substituted Hydroxyapatite Powders

Hydroxyapatite (HA) and fluor‐hydroxyapatite (FHA) powders were synthesized by a sol–gel method for usage as bone filler and drug carrier. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol–water‐based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of FHA powders. With heat treatment above 400°C, a characteristic apatite phase was observed for all the sol–gel powders. However, the crystallization temperature decreased with increasing fluoride addition. The tricalcium phosphate (TCP) phase formed in the pure HA powder above 800°C was attenuated in the FHA powders, confirming an enhanced phase stability of the FHA powders. Increasing the F− addition improved crystallinity and increased the crystallite size, as was determined from X‐ray diffraction (XRD) analyses. The lattice parameters of the heat‐treated powders varied corresponding to the fluoride addition, i.e., a gradual decrease in the a‐axis, while little change in the c‐axis was observed with increasing fluoride addition, indicating a nearly complete substitution of fluoride within the apatite lattice. However, little difference was observed with heat‐treatment temperatures (400°–1000°C). The powders substituted with fluoride exhibited reduced dissolution rates in an in vitro solution as compared with the pure HA powder, suggesting the possibility of tailoring bioactivity with fluoride substitution.

Synthesis of thioglycoside-based UDP-sugar analogues.

Arbuzov reaction of O-acetyl-protected glycosylthiomethyl chlorides with triethyl phosphite and then phosphonate ethyl ester cleavage with trimethylsilyl bromide afforded glycosylthiomethyl phosphonates 13, 18, 22, and 26. These intermediates could be readily transformed into the O-deprotected phosphonates 7-10 and into title compounds 1-4. Similarly, sulfonomethyl phosphonate moieties containing UDP-sugar analogues 5 and 6 were obtained.

Synthesis of Nitrated Thienylphosphonates via Michaelis—Arbuzov‐Type Rearrangement.

AbstractFor Abstract see ChemInform Abstract in Full Text.

α‐Alkyl(aryl)sulfenyl Substituted β‐Ketophosphonates: Synthesis, Properties and Reactivity.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hydroxyapatite and fluor-hydroxyapatite layered film on titanium processed by a sol-gel route for hard-tissue implants.

A double-layered coating, consisting of a hydroxyapatite (HA) outer film and a fluor-hydroxyapatite (FHA) inner film, was produced on a Ti substrate by a sol-gel route to improve the biocompatibility and functionality of the system. Dissolution behavior of and in vitro cellular responses to the layered film were investigated. Calcium nitrate and triethyl phosphite were used for calcium and phosphate precursors, respectively, and ammonium fluoride was added as a fluorine-ion source for FHA. The FHA layer was deposited on Ti by spin coating and subsequent heat treatment at 550 degrees C for 30 min in air, and then the HA layer was laid down over the FHA-coated Ti under the same conditions. After heat treatment, characteristic apatite structures and phases were developed on both FHA and HA films. The cross-section view of the HA/FHA film clearly showed a double-layered structure on Ti with each layer approximately 0.6-0.8-microm thickness. The coating layer was highly uniform and dense, and adhered to Ti substrate strongly with an adhesion strength of about 40 MPa. The in vitro solubility of the HA/FHA layered film in a physiological solution was between that of HA and FHA pure film, and the dissolution profile was quite biphasic, that is, an initial rapid period and a slowdown with increasing time, reflecting the gradient solubility of the fast HA outer structure/slow FHA inner structure. The human osteoblast-like HOS TE85 cells cultured on the HA/FHA layered film attached, spread, and grew favorably. The proliferation rate of the cells on the layered film was significantly higher (considered at p < 0.05 for n = 6) than that on Ti substrate and was similar to that on pure HA film. The alkaline phosphatase (ALP) activity and osteocalcin (OC) produced by the cells on the layered film were significantly higher (considered at p < 0.05 for n = 6) than those on Ti substrate. Moreover, the ALP and OC levels of cells on the layered film showed the trends of HA outer/FHA inner structure with respect to culture period, that is, HA initially and FHA later. These observations suggest that the HA/FHA layered film on Ti obtained by a sol-gel route possesses gradient functionality in terms of solubility and cellular responses, and find that those parameters can be tailored for specific use in hard-tissue implants.

Chemoselective Glycosylations Using Sulfonium Triflate Activator Systems.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Phosphono‐Substituted Isoindolines and Indoles from 2,3‐ and 2,4‐Benzoxazin‐1‐ones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of substituted BEDT-TTF derivatives for the preparation of bifunctional materials

Short synthetic approaches to a range of monosubstituted BEDT-TTF derivatives are described, via either cycloaddition reactions of 1,3-dithiole-2,4,5-trithione or nucleophilic substitutions of 2-thioxo-1,3-dithiole-4,5-dithiolate, followed by reaction with mercuric acetate and then coupling in the presence of triethyl phosphite. BEDT-TTF derivatives with hydroxy- and amino-functionalised side chains have been prepared with the functional group protected. Deprotection and further reactions opens up potential for attachment to groups bringing additional bulk properties, e.g. groups such as pyridine and 2,2'-bipyridine for binding magnetic metal ions, and electropolymerisable groups such as thiophenes and pyrroles. Preparation of BEDT-TTF's carrying carbonyl functionalities are also described. Strategies for preparing polysubstituted donors are discussed.

α-Alkyl(aryl)sulfenyl substituted β-ketophosphonates: synthesis, properties and reactivity

A new synthesis of the title compounds via acylation of α-lithio-α-phosphorylalkyl sulfides is described. Two additional approaches to these compounds, although less efficient, involve: (a) sulfenylation of O-silylated dialkyl β-ketophosphonates and (b) the Arbuzov reaction of triethyl phosphite with α-chloro-α-methylthiomethyl phenyl ketone. The keto–enol tautomerism of the title compounds and reactivity of the anions derived from them with electrophilic reagents were investigated. The P(O)-olefination products obtained from electron rich aromatic aldehydes were found to undergo the acid-catalyzed desulfenylation reaction affording α,β-unsaturated ketones.

A Novel Seven‐Membered Carbohydrate Phostone.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Calcium phosphate sol–gel-derived thin films on porous-surfaced implants for enhanced osteoconductivity. Part I: Synthesis and characterization

Thin sol–gel-formed calcium phosphate (Ca-P) films were formed on sintered porous-surfaced implants as an approach to increasing the rate of bone ingrowth. The films were prepared using either an inorganic precursor solution (with calcium nitrate tetrahydrate and ammonium dihydrogen phosphate) or an organic precursor solution (with calcium nitrate tetrahydrate and triethyl phosphite). We report on the formation and characteristics of the films so formed. Film characteristics were assessed by thin film X-ray diffraction, diffuse-reflectance infrared Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. In addition, thin sections were prepared either across or parallel to the Ca-P/Ti6Al4 V interface and examined by transmission electron microscopy. Both approaches resulted in the formation of nanocrystalline carbonated hydroxyapatite films but with different Ca/P ratios and structures, the Inorganic Route-formed film having a lower Ca/P ratio (1.46 cf 2.10 for the Organic Route-formed film) and having a more irregular topography. An interfacial reaction product (CaTi 2O 5) was identified by selected area electron diffraction with the Inorganic Route-formed film only.

Hexachloroacetone as a precursor for a tetrachloro-substituted oxyallyl intermediate: [4+3] cycloaddition to cyclic 1,3-dienes.

The enol phosphate 2,2-dichloro-1-(trichloromethyl)ethenyl diethyl phosphate (1), easily available by a Perkow reaction between hexachloroacetone and triethyl phosphite, reacts with sodium trifluoroethoxide/trifluoroethanol in the presence of cyclic 5-membered 1,3-dienes to furnish alpha,alpha,alpha',alpha'-tetrachloro-substituted[3.2.1]bicyclic ketones 2. A [4+3] cycloaddition of a tetrachloro-oxyallyl intermediate is postulated.

A Convenient Method for the Synthesis of Electron‐Rich Phosphonates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of Nitrated Thienylphosphonates via Michaelis-Arbuzov-Type Rearrangement

A facile, catalyst-tree synthesis of diethyl thienylphosphonates under mild conditions without solvent is described. The desired products were obtained, via a Michaelis-Arbuzov-type rearrangement, from various activated thienyl halides by reacting with triethyl phosphite.

Observation of a non-conventional Horner–Wadsworth–Emmons olefination product and the effect of the lateral ethyl substitution on the solid state fluorescence

Donor-acceptor-substituted diphenylbutadienes, namely 1-(p-methoxyphenyl)-4-(p-cyanophenyl)buta-1E,3E-diene (MCB) and 1-(p-N,N-dimethylaminophenyl)-4-(p-cyanophenyl)buta-1E,3E-diene (ACB) exhibit fluorescence properties in their solid that are distinctly different from their fluorescence in solution. The red-shifted absorption and emission spectra observed in the solid state are attributed to the formation of J aggregates. Preparation of these derivatives via a Horner–Wadsworth–Emmons reaction, wherein the phosphonate obtained by treating p-cyanobenzyl bromide with triethyl phosphite was condensed with corresponding cinnamaldehydes, also yielded the non-conventional olefination products 1-(p-methoxyphenyl)-4-(p-cyanophenyl)-4-(ethyl)buta-1E,3E-diene (MCBE) and 1-(p-N,N-dimethylaminophenyl)-4-(p-cyanophenyl)-4-(ethyl)buta-1E,3E-diene (ACBE), which bear an ethyl group substituent on their butadiene chain. The formation of these products suggests a base-catalyzed 1,3-migration of an ethyl group from an oxygen center to the benzylic position in the initially formed phosphonate. The presence of the ethyl group in an otherwise planar molecule was observed to significantly hinder aggregation in the solid state, resulting in molecule-like fluorescence even in their bulk state.