Synthesis and selected reactions of ethyl 5-(1-chloroethyl)-2-methylfuran-3-carboxylate

Ethyl 2-methylfuran-3-carboxylate is smoothly chloroethylated at 0°C in the 5 position of the ring. The resulting halide alkylates secondary amines but eliminates HCl with sodium diethyl phosphite under the Michaelis-Becker reaction conditions and with trimethyl phosphite under the Arbuzov reaction conditions. In the reaction with sodium diethyl phosphite, small amounts of 5-[1-(diethoxyphosphoryl)ethyl]furan-3-carboxylate and 5-ethylfuran-3-carboxylate are formed. In the Arbuzov reaction at a 1: 1.22 furan: trimethyl phosphite molar ratio, methyl 2,4-dimethyl-1-methoxy-1-oxo-1λ⁵-1,2-dihydrophospheto[3,2-b]furan-5-carboxylate was isolated.     

Cyclisation reactions of 2-substituted benzoylphosphonates with trialkyl phosphites via nucleophilic attack on a carbonyl-containing ortho substituent

Dimethyl 2-acetoxy- and dimethyl 2-benzoyloxy-benzoylphosphonate undergo cyclisation and deoxygenation in the presence of excess trimethyl phosphite to give dimethyl (3-methyl-1-benzofuran-2-yl)phosphonate and dimethyl (3-phenyl-1-benzofuran-2-yl)phosphonate, respectively. The reaction pathway has been shown to involve phosphite attack on initially formed tricyclic dioxaphospholane intermediates with the subsequent loss of two molecules of trimethyl phosphate. In the absence of additional trimethyl phosphite the initially formed tricyclic dioxaphospholane intermediates lose one molecule of trimethyl phosphate and then undergo a novel rearrangement to give β-ketophosphonates. The mechanism for this reaction helps explain some previously reported epoxide rearrangements. In contrast, the initially formed anionic intermediate from the reaction of dimethyl 2-benzoyloxymethylbenzoylphosphonate with trimethyl phosphite undergoes decomposition to give a carbene intermediate which is trapped by the trimethyl phosphite to give an ylidic phosphonate.     

A convenient method for the preparation of chiral phosphonoacetamides and their Horner–Wadsworth–Emmons reaction

Chiral phosphonoacetamides bearing (S)-(α-methylbenzyl)benzylamine, (S,S)-bis(α-methylbenzyl)amine, l-phenylglycine methyl ester and l-phenylglycinol were easily prepared in good yield by means of the Michaelis–Arbuzov reaction of chiral bromoacetamides obtained in quantitative yield, with trimethyl phosphite, which under Horner–Wadsworth–Emmons conditions with several aryl and alkyl aldehydes under Masamune–Roush procedure using LiCl and DBU in THF or toluene gave the corresponding chiral α,β-unsaturated amides. The present procedure is a convenient and efficient methodology for the preparation of phosphonoacetamides and chiral α,β-unsaturated amides in high E-selectivity.     

Novel synthesis of triblock PDMS-PS-PDMS copolymers

Benzyl 6-(2′-pentamethyldisiloxanyl ethyl)-ortho-tolyl ketone (I) was prepared by a ruthenium-catalyzed Murai reaction of benzyl ortho-tolyl ketone with vinyl pentamethyldisiloxane. The reaction of I with a mixture of styrene and a catalytic amount of picoline Cu(II) acetate yielded the telechelic polystyrene α,ω-bis(2-pentamethyl-disiloxanyl ethyl)polystyrene (III). The acid-catalyzed equilibration polymerization of octamethylcyclotetrasiloxane into the Si O Si bonds of telechelic III yielded the polydimethylsiloxane-polystyrene-polydimethylsiloxane triblock soft–hard–soft copolymer. The molecular weights of the copolymers were studied by ¹H NMR end-group analysis and gel permeation chromatography. The thermal properties and morphology of IV were examined by differential scanning calorimetry and transmission electron microscopy (TEM). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 482–488, 2000     

Synthesis and spectroscopy of phosphonate derivatives of uracil and thymine. X-ray crystal structure of diethyl 6-uracilmethylphosphonate

A new class of phosphonate ligands, derived from uracil and thymine was designed, prepared and characterised. Dimethyl ( 4, 7 ) and diethyl ( 5, 8 ) uracilmethylphosphonates have been prepared by the reaction of chloromethyluracil isomers 2 and 3 with trimethyl phosphite and triethyl phosphite, respectively. The corresponding free acids, 5-uracilmethylphosphonic acid 6 and 6-uracilmethylphosphonic acid 9 , have also been isolated. The structure of the compounds has been assigned by nmr spectroscopy and, in the case of 8 , confirmed by X-ray analysis.     

Synthesis and characterization of bis(methoxyl hydroxyl)-functionalized disiloxane and polysiloxane oligomers derivatives therefrom

With purpose to prepare waterborne polyurethane with improved performance, bis(methyoxyl hydroxyl)-functionalized polysiloxanes with different dimethylsiloxane segment length were prepared. The preparation includes three steps, the first is synthesis of 1,3-bis(glycidoxypropyl)tetramethyldisiloxane (compound I) via hydrosilylation of allylglycidyl ether with tetramethyldisiloxane, followed by a subsequent methoxylation of the resultant compound from the hydrosilylation to give 1,3-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)tetramethyldisiloxane (compound II). Using this compound II and octamethylcyclotetrasiloxane (D₄), an equilibrium reaction was carried out to obtain the target Product III, i.e. bis(methoxyl hydroxyl)-functionalized polysiloxanes. The ratio of D₄/compound II was varied in order to prepare product III with different segment length consisting of dimethylsiloxane units. At each step, the outcome compounds were characterized through Infrared, ¹H NMR, ¹³C NMR as well as H-H and H-C Correlated Spectroscopy (COSY). The results showed that each step was successfully carried out and objective products were achieved. It was estimated that compound II was not exclusive in the methoxylation step. Characterizations of the compound II enabled us to give a reliable quantitative amount for the by-products for the first time. In addition, the molecular weights of the final product III with varying dimethylsiloxane length were estimated by hydroxyl group analysis, ¹H NMR and GPC, which showed a good agreement between the theoretical molecular weights and those from these tests.     

Treatment of dimethyl (+)-L-tartrate with sulfur tetrafluoride

Treatment of dimethyl (+)-L-tartrate (I) with sulfur tetrafluoride results in the formation of an intermediate, 2-fluoro-1,2-bis(methoxycarbonyl)ethyl fluorosulfite (II), which under the action of hydrogen fluoride, present in the reaction mixture, is converted into dimethyl (?)(2S:3S)-2-fluoro-3-hydroxysuccinate (III). The reaction of the latter with SF₄ leads to dimethyl meso-2,3-difluorosuccinate (IV). The structure and configurations of the compounds obtained were established by ¹H and ¹⁹F NMR. Treatment of dimethyl (+)-L-tartrate (I) with sulfur tetrafluoride in the presence of excessive hydrogen fluoride gave dimethyl meso-2,3-difluorosuccinate in 96% yield.     

Determination of the fragmentation mechanisms of organophosphorus ions by H2O and D2O atmospheric-pressure ionization tandem mass spectrometry

Dimethylmethyl phosphonate (DMMP), dimethyl phosphite (DMPI), trimethyl phosphite (TMPI) and trimethyl phosphate (TMP) were investigated using H₂O and D₂O atmospheric-pressure ionization (API) tandem mass Spectrometry. All daughter ions could be explained by losses of one or a successive number of stable molecules as opposed to losses of radicals such as the hydride, methyl and methoxy species. Losses of neutral methanol and dimethyl ether and of protonated methanol and formaldehyde ions from all four organophosphorus pseudo-molecular ions were observed. The DMMP and DMPI MH⁺ pseudomolecular ions produced the losses of neutral C₂H₆ and water, respectively. Formaldehyde loss was not observed for the MH⁺ ions, but it was well represented in the decomposition pathways of daughter ions. The D₂O reagent gas highlighted the role of the ionizing proton/ deuteron in the various daughter ions, including m/z 95, 79, 65, 49, 33, 31 and 47. The last ion was found to be isobaric in that m/z 47 and 48 both appeared with similar abundances in the D₂O-API daughter ion mass spectra of TMPI and TMP.     

THE STEREOCHEMISTRY OF DEALKYLATION STEP IN THE ARBUZOV REACTION INVOLVING FIVE-COORDINATE INTERMEDIATE. EVIDENCE FOR EQUILIBRIUM BETWEEN PHOSPHORANE AND PHOSPHONIUM SPECIES

Abstract

The oxidative addition of molecules X–Y to three-coordinated phosphorus compounds is of considerable general interest. If one of the groups attached to the phosphorus atom is an alkoxy, OR, the final product is almost always > P(O)Y with the formation of an alkyl halide RX. The above process is known as Arbuzov reaction, the mechanism of which can be represented, in the light of our present knowledge, as follows: mental mechanistic problem for the Arbuzov reaction.

The R(?)phosphite (4) was prepared from R(+)2-octanol of 95% opt. purity, [α]²⁰ _D + 9.4° (neat) and the chlorophosphite (3) by standard condensation in the presence of tertiary amine and purified by distilla tion in vacuo, δ³¹P ?127.5 ppm, [α]^D ₂₀ ?25.6° (neat). Equimolar amounts of the phosphite (4) and the corresponding halogen in CH2 C12 solution were allowed     

Enhanced thermal stability of poly(p-dioxanone) in melt by adding an end-capping reagent

For the enhancement of thermal stability of poly(p-dioxanone) (PPDO), the isocyanate end-capping reagent was prepared by treatment of toluene-2,4-diisocyanate with an equivalent of 1-hexyl alcohol. The end-capping reagent and the end-capping PPDO with an inherent viscosity of 0.26 dL g⁻¹ were characterized by FTIR and ¹H-NMR. Thermal stability of the end-capping PPDO with an inherent viscosity of 0.92 dL g⁻¹ was investigated isothermally and non-isothermally under air atmosphere using thermogravimetry. It has been shown that the addition of the prepared isocyanate can enhance significantly the thermal stability of PPDO. The activation energies for non-isothermal degradation estimated by Kissinger method and Friedman method are 91, 81 kJ mol⁻¹ for as-prepared PPDO, and 160, 149 kJ mol⁻¹ for the end-capping PPDO, respectively. The activation energy increases by about 70 kJ mol⁻¹ through the end-capping.     

Gas-phase ion-molecule reactions in organophosphorus esters

Self-condensation ion-molecule reactions of trimethyl phosphite, triethyl phosphite, dimethyl phosphonate, trimethyl phosphate and 2, 2-dichlorovinyl dimethyl phosphate (dichlorvos) were investigated by ion trap mass spectrometry and Fourier transform ion cyclotron resonance mass spectrometry. Reaction paths for the main processes observed were elucidated by parent ion selection and for reaction times up to 500 ms. In parallel, high-resolution measurements were performed in order to determine the composition of the principal ions. Among the compounds under examination, trimethyl phosphite and triethyl phosphite mainly give [M + H](+) and [M + (RO)(2)P](+) (R = CH(3), C(2)H(5)) adduct ions, whereas trimethyl phosphate and dimethyl phosphonate display [2M + H](+) ions, as the only abundant products, formed by reaction of [M + H](+) and M. 2,2-Dichlorovinyl dimethyl phosphate mostly shows fragmentation processes. The reaction patterns of the compounds examined were related to their different structural features. Gas-phase basicities of the phosphoryl compounds were also determined or re-examined. Copyright 1999 John Wiley & Sons, Ltd.     

Wittig-horner reaction of a phosphonate of reissert analogue a new method for introduction of alkyl groups into isoquinoline

Dimethyl 2-isopropoxycarbonyl-1, 2-dihydroisoquinoline-1-phosphonate ($\text{1}$) was prepared from isoquinoline, isopropyl chloroformate, and trimethyl phosphite. Wittig-Horner reaction of $\text{1}$ with various aldehydes afforded the corresponding exo-methylene compounds, which were converted to 1-substituted isoquinolines with hydrogen chloride.     

Stabilization of Hydroxy Tautomeric Form of Dimethyl Phosphite in the Coordination Sphere of Carbonyl Complexes of Group VI Metals

The interaction of dimethyl phosphite with hexacarbonyls of the chromium group metals in a nonpolar solvent has afforded metal(0) σ⁴,λ⁴-(dimethyl phosphite)pentacarbonyls containing a hydroxy tautomeric form of dimethyl phosphite in the coordination sphere. Hydrogen of the phosphite OH group in the metal(0) σ⁴,λ⁴-(dimethyl phosphite)pentacarbonyls exhibited a significant acidity, strongest for the chromium complexes. Due to the significant acidity of the phosphite hydroxyl, the metal(0) σ⁴,λ⁴-(dimethyl phosphite)-pentacarbonyls are intermediates in the electrophilic version of the Pudovik reaction.     

Synthesis of Dimethyl (m-Carboran-9-yl)phosphonate and Dimethyl (p-Carboran-2-yl) Phosphonate by Palladium-catalyzed Cross Coupling of 9-I-m- and 2-I-p-Carboranes with Dimethyl Hydrogen Phosphite

Dimethyl (m-carboran-9-yl)- and (p-carboran-2-yl)phosphonates were prepared by (Ph₃)₄Pd-catalyzed cross coupling of 9-I-m- and 2-I-p-carboranes with dimethyl hydrogen phosphite in the presence of triethylamine.     

Liquid-liquid extraction of group IB metal ions by thioethers

Liquid-liquid extraction of metal ions by means of organic extractants possessing divalent sulfur (thioethers) is discussed. it is shown that 1,2-bis(hexylthio)ethane (BHTE) and 13,14-benzo-1,4,8,11-tetrathiacyclopentadecane (TTX) are powerful extractants for soft metal ions such as copper(I), Silver(I), and gold(I). The same is true for the trivalent phosphorus compounds, triphenylphosphine and phosphite tristers, which were studied for comparison. Copper(II) and gold(III) are efficiently extracted with thioethers in combination with reducing agents. From an equilibrium study for the extraction of copper(I) and silver(I) by BHTE (L), a complex of the type ML₂X (M⁺, metal ion; X^?, anion) was proved to be extracted. In the extraction of gold, the combined use of a thioether and phosphite enhanced the extractability of the metal, compared with the independent use of these extractants; the synergism is discussed. Further, the reductive extractions of copper(II) and gold(III) were coupled with a photo-redox reaction, leading to light-induced extraction of these metal ions.     

Studies of the Reactions of 2-Substituted Dimethyl Benzoylphosphonates with Trimethyl Phosphite

Abstract

Dimethyl benzoylphosphonates (1) react with trimethyl phosphite to give anionic intermediates (2) which decompose to give carbenes (3) and trimethyl phosphate [1]. When suitable ortho-substituents are present on the benzoylphosphonate, intramolecular carbene insertion reactions can occur to give cyclic systems. With alkyl substitutents, where the length of the chain provides a choice of cyclisation pathways, insertion into an appropriate C[sbnd]H bond to give a 5-membered ring has been found to be the preferred option. We have therefore been investigating the behaviour of systems, such as (4), where insertion into a C[sbnd]H bond to give a 5-membered ring is prevented.     

1,3-Adamantanyl dimethylsiloxane copolymers. Preparation and properties

1,3-bis(Dimethylhydroxysilyl)adamantane(I) has been prepared. Thermal condensation polymerization of this monomer yields poly-1,3-adamantyl-1,1,3,3-tetramethyldisiloxane. Condensation of I with bis(dimethylamino)dimethylsilane or 1,3-bis(dimethylamino)-1,1,3,3-tetramethyldisiloxane gave the expected 1,3-adamantyl dimethylsiloxane copolymers (II and III) respectively. These polymers have been characterized by ¹H,¹³C, and ²⁹SiNMR as well as GPC and TGA. They have unusually high thermal stability.     

Reaction of 2,4-Difunctional Esters of 5-tert-Butylfuran-3-carboxylic Acid with Nucleophilic Reagents

Ethyl 5-tert-butyl-4-(chloromethyl)-2-methylfuran-3-carboxylate was brominated with N-bromo-succinimide to obtain the corresponding 2-bromomethyl derivative. The latter is selectively phosphorylatedwith trimethyl, triethyl phosphites by the bromomethyl group. The resulting [4-(chloromethyl)furyl]methyl-phosphonates in the presence of secondary amines and sodium butanethiolate behave as alkylating agents,while sodium phenolate causes their decomposition. 4-Acetoxymethyl- and 4-phenoxymethyl derivatives of the starting product are also selectively brominated with N-bromosuccinimide by the 2-methyl group. The first of the 2-(bromomethyl)furans formed is smoothly phosphorylated with trimethyl phosphite, while the second one under the action of triethyl phosphite gives a mixture of phosphorylation and debromination products. In all the cases, an additional electron-acceptor group in position 4 of alkyl 2-(bromomethyl)-5-tert-butylfuran-3-carboxylate considerably accelerates the Arbuzov reaction.     

Synthesis of dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylates via a one-pot and four-component reaction

A number of new dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylate derivatives have been prepared regiospecifically in moderate to good yield from the cyclocondensation reaction of dialkyl (E)-2-(dialkoxyphosphoryl)-3-(aroyl)-2-butenedioate, derived from the reaction between trimethyl phosphite, an acetylenic ester, and an aroyl chloride, with phenylhydrazine. The reaction is four-component and is carried out under reflux conditions in dry toluene.     

Synthesis and thermal crosslinking of benzophenone‐modified poly(dimethylsiloxane)s

Dihydridocarbonyltris(triphenylphosphine)ruthenium catalyzes the regiospecific anti‐Markovnikov addition of an ortho C? H bond of benzophenone across the C? C double bonds of α,ω‐bis(trimethylsilyloxy)copoly(dimethylsiloxane/vinylmethylsiloxane) (99:1), α,ω‐bis(vinyldimethylsilyloxy)poly(dimethylsiloxane), and 1,3‐divinyltetramethyldisiloxane to yield α,ω‐bis(trimethylsilyloxy)copoly[dimethylsiloxane/2‐(2′‐benzophenonyl)ethylmethylsiloxane]), α,ω‐bis[2‐(2′‐benzophenonyl)ethyldimethylsilyloxy]poly(dimethylsiloxane), and 1,3‐bis[2‐(2′‐benzophenonyl)ethyl]tetramethyldisiloxane, respectively. These materials have been characterized with ¹H, ¹³C, and ²⁹Si NMR and IR spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography. The thermal stability of the polymers has been measured by thermogravimetric analysis, and their glass‐transition temperatures (T_g's) have been determined by differential scanning calorimetry. The molecular weight distribution, thermal stability, and T_g's of the modified polysiloxanes are similar to those of the precursor polymers. The molecular weights of these materials can be significantly increased via heating to 300 °C for 1 h. This may be due to crosslinking, by pyrocondensation, of pendant anthracene groups, which are produced by the pyrolysis of the attached ortho‐alkyl benzophenones. UV spectroscopy of the pyrolysate of 1,3‐bis[2‐(2′‐benzophenonyl)ethyl]tetramethyldisiloxane has confirmed the presence of pendant anthracene groups. Thermal crosslinking by the pyrocondensation of pendant anthracene groups has been verified by the pyrolysis of α,ω‐bis(trimethylsilyloxy)copoly[dimethylsiloxane/2‐(9′‐anthracenyl)ethylmethylsiloxane] (97:3). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5514–5522, 2004