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.     

Electron-rich heteroaroylphosphonates and their reaction with trimethyl phosphite

Dialkyl heteroaroylphosphonates based on thiophene, pyrrole or furan have been prepared and their reactions with trimethyl phosphite investigated. Deoxygenation of the carbonyl groups in these heteroaroylphosphonates occurs to give carbene intermediates, which then undergo further reaction. In the case of the furan-3-oylphosphonates and those systems containing a thiophene or pyrrole ring, the major reaction pathway involves intermolecular trapping of the carbene intermediates by the trimethyl phosphite, leading to the formation of ylidic phosphonates that can be readily converted into the corresponding 1,1-bisphosphonates. However, in some furan-2-oylphosphonates the carbenes generated undergo ring-opening to initially give acyclic alkynylphosphonates which may react further to give other novel phosphorus compounds. The effects of substituents on the extent to which intermolecular trapping of the initially formed carbene competes with intramolecular rearrangement has been investigated. The latter process appears to be suppressed by a substituent at the 5-position of the furan ring, the resulting ylidic phosphonates being a rare example of an efficient intermolecular trapping of a furan-2-yl carbene.     

Reaction between naphthols and dimethyl acetylenedicarboxylate in the presence of phosphites. Synthesis of stable oxa-2 lambda 5-phosphaphenanthrenes,and benzochromene derivatives

The reaction of dimethyl acetylenedicarboxylate (DMAD) with 2-naphthol in the presence of trimethyl or triphenyl phosphite leads to stable dimethyl oxa-2 lambda 5-phosphaphenanthrene derivatives in good yields. The reaction of DMAD and trimethyl phosphite in the presence of 1-naphthol or 8-hydroxyquinoline leads to dimethyl 2-(dimethoxyphosphoryl)-3-(1-hydroxy-2-naphthyl)succinate or dimethyl 2-(dimethoxyphosphoryl)-3-(8-hydroxyquinolin-7-yl)-succinate in excellent yields. Using triethyl phosphite and DMAD in the presence of 2-naphthol or 1-naphthol produces methyl 3-oxo-2,3-dihydro-1H-benzo[f]chromene-1-carboxylate or methyl 2-oxo-3,4-dihydro-2H-benzo[h]-chromene-4-carboxylate in excellent yields.     

Reactions of Dimethyl Heteroaroylphosphonates with Trialkyl Phosphite in the Presence of Proton Donors

Abstract

We have previously shown that substituted bcnzoylphosphonates (1; Ar ? X-Ph) react with trimethyl phosphite to give anionic intermediates which in the absence of electrophiles decompose to give carbene intermediates (3). The nature of the subsequent reaction products depends on the type and position of the substituents on the aromatic ring.ll1 When proton donors are present the initially formed anionic intermediates (2) give the quasi-phosphonium salts (4) which usually decompose to give the phohphonate-phosphates (5). although for the case of (1; Ar ? 4-MeOPh) formation of the phosphonates (6) was observed.     

Specific Features of Reactions of Halomethyl Derivatives of Alkyl 5-Isobutylfuran-3-carboxylates with Trimethyl Phosphite and Sodium Diethyl Phosphite

Ethyl 5-isobutyl-2-methylfuran-3-carboxylate is selectively brominated with N-bromosuccin-imide by the methyl group to give an unstable bromide. The latter on heating or in the presence of bases un-dergoes dehydrobromination accompanied by rearrangement, leading to a (2'2-dimethylvinyl)furan derivative.Phosphorylation of this bromide with trimethyl phosphite gives a 2-dimethoxyphosphorylmethyl derivativeand a product containing the phosphonate group to the isobutyl radical. Chloromethylation of the startingester proceeds in the 4 position of the furan ring. The resulting chloride undergoes phosphorylation underconditions of the Michaelis-Becker reaction to give the corresponding 4-(dialkoxyphosphorylmethyl)furan'and under the action of trimethyl phosphite a mixture of the same phosphonate, a dehalogenation producthaving a dimethylvinyl fragment. Bromination of the 4-chloromethyl derivative with N-bromosuccinimideinvolves the 2-methyl group. The dihalide reacts with trimethyl phosphite by way of reduction of the bromomethyl group to give 4-chloromethyl- or 4-dimethoxyphosphorylmethyl derivatives, as well as analogous dehydrohalogenation products containing a 5-dimethylvinyl fragment. A scheme describing the sequence of formation of these products in the course of the reaction is offered.     

Preparation and properties of dimethyl phosphonomethyl methylsiloxane dimethylsiloxane copolymers

Dimethyl phosphonomethylheptamethylcyclotetrasiloxane (II) and 1, 3-bis(dimethyl phosphonomethyl)tetramethyldisiloxane (III) have been prepared by Arbuzov reaction of trimethyl phosphite with bromomethylheptamethylcyclotetrasiloxane (I) and 1, 3-bis(bromomethyl)tetramethyldisiloxane, respectively. Dimethyl phosphonomethylmethylsiloxane dimethylsiloxane copolymers have been prepared by acid-catalyzed ring-opening polymerization of II with hexamethyldisiloxane (MM) as an end-capping reagent and by reaction of II with III as an end-capping reagent. Dimethylsiloxane polymers with dimethyl phosphonomethyldimethylsiloxy end groups have been prepared by acid-catalyzed polymerization of octamethylcyclotetrasiloxane (D₄) and III. Under these conditions hydrolysis of the dimethyl phosphonate ester groups was a problem. On the other hand Arbuzov reaction of trimethyl phosphite with bromomethylmethylsiloxane dimethylsiloxane copolymer gave a dimethyl phosphonomethylmethylsiloxane dimethylsiloxane copolymer with uniform properties. These polymers have been characterized by ¹H-, ¹³C-, ²⁹Si-, and ³¹P-NMR spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography (GPC) and their thermal stability measured by TGA.     

FACTORS IN THE CONTROL OF PRODUCT COMPOSITION IN THE REACTIONS OF TRIALKYL PHOSPHITES WITH α-HALOGENOACETOPHENONES IN ALCOHOLIC MEDIA

Abstract

α-Hydroxyphosphonates are formed, in addition to vinyl phosphates and dehalogenated ketones, in the reactions of trimethyl phosphite (in methanol) or triethyl phosphite (in ethanol) with variously substituted α-chloro, α-bromo, and α,α-dichloro-acetophenones. Tri-isopropyl phosphite in propan-2-ol gives only the vinyl phosphate. Ketophosphonates are not detectable amongst the reaction products under the conditions used. Trends in product composition can be correlated with the leaving ability of halogen, substituent effects, structure of the phosphite, and reaction temperature. Additional products are obtained in the reactions of trimethyl phosphite in methanol with 4-nitro-α-chloroacetophenone, which gives the dehalogenated hydroxyphosphonate, and with the α,α-dichloroacetophenones which undergo monodehalogenation. Twenty three new α-hydroxyphosphonates are reported.     

Gas-phase reactivity of the O=P(OCH3)2 + phosphonium ion towards alpha,beta-unsaturated esters in a quadrupole ion trap

Ion-molecule reactions between the O=P(OCH3)2 + phosphonium ions and eight alpha,beta-unsaturated esters (methyl acrylate, ethyl acrylate, methyl crotonate, ethyl crotonate, methyl 3,3-dimethylacrylate, ethyl 3,3-dimethylacrylate, methyl methacrylate and ethyl methacrylate) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH3)2 + phosphonium ions, formed by electron ionization from neutral trimethyl phosphite, were found to react with alpha,beta-unsaturated esters to give an adduct [RR'C=CR'COOR', O=P(OCH3)2]+, which lose spontaneously a molecule of trimethyl phosphate (R'=CH3) or dimethyl ethyl phosphate (R'=C2H5). An ion corresponding to a protonated trialkyl phosphate is also observed when substituent R'=H. To confirm the experimental results, and to elucidate the mechanism for the formation of the ionic species, a theoretical study using the density functional theory (DFT) approach was carried out. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH3)2 + and methyl acrylate is described.     

The Behavior of 3,3-Diphenylindan-1,2-dione Towards Alkyl Phosphites

The reaction of 3,3-diphenylindan-1,2-dione with trimethyl phosphite in dry benzene at room temperature for about 15 h led to the formation of a mixture containing dimethyl (3,3-diphenyl-2-methoxy-1-indenyl)phosphate and dimethyl (3,3-diphenyl-1H-2-oxo-1-indanyl)phosphate, whereas with triisopropyl phosphite, diisopropyl (3,3-diphenyl-2-isopropoxy-1-indenyl)phosphate is the only product. Treatment of the dione with dialkyl phosphites under different experimental conditions gave dialkyl (3,3-diphenyl-1-hydroxy-2-oxo-1-indanyl)phosphates. Reaction mechanisms are presented which account for the experimental results. Structural assignments of the new compounds are based on the spectroscopic evidences and two examples were elucidated by X-ray crystallography.     

The Behavior of 3,3-Diphenylindan-1,2-dione Towards Alkyl Phosphites

Summary. The reaction of 3,3-diphenylindan-1,2-dione with trimethyl phosphite in dry benzene at room temperature for about 15 h led to the formation of a mixture containing dimethyl (3,3-diphenyl-2-methoxy-1-indenyl)phosphate and dimethyl (3,3-diphenyl-1H-2-oxo-1-indanyl)phosphate, whereas with triisopropyl phosphite, diisopropyl (3,3-diphenyl-2-isopropoxy-1-indenyl)phosphate is the only product. Treatment of the dione with dialkyl phosphites under different experimental conditions gave dialkyl (3,3-diphenyl-1-hydroxy-2-oxo-1-indanyl)phosphates. Reaction mechanisms are presented which account for the experimental results. Structural assignments of the new compounds are based on the spectroscopic evidences and two examples were elucidated by X-ray crystallography.     

Laser flash photolysis evidence for styryl radical cation cyclization in the SET-induced photorearrangement of a p-methoxy-substituted 2-phenylallyl phosphite

The SET-induced photorearrangement of dimethyl 2-(4-methoxyphenyl)allyl phosphite, 9 (UV light, uranium glass filter, 9,10-dicyanoanthracene (DCA), biphenyl), gives phosphonate 12 in 83% isolated yield. Laser flash irradiation at 355 nm of oxygen saturated solutions of phosphite 9 containing DCA and biphenyl generates the transient UV spectrum of the biphenyl radical cation that is quenched by electron transfer from phosphite 9 (k(q) = 8.9 x 10(9) M(-1) s(-1) at 20 degrees C) to form the 4-methoxystyryl cation 10. The UV spectrum of 10 decays by a measured first-order rate constant of 8.0 x 10(6) s(-1), presumably to generate the cyclic distonic radical cation 11. Intermediate 10 was further characterized by measurement of the second-order rate constants for its reaction with azide, chloride, and bromide ions and with the neutral nucleophile trimethyl phosphite. This study provides the first spectroscopic evidence regarding the proposed mechanism (Schemes 1 and 2) for the SET-induced photorearrangements of dimethyl 2-arylallyl phosphites to the corresponding 2-arylallylphosphonates. Moreover, absolute rate constants for the intramolecular trapping of alkene radical cations have seldom been measured. The removal of the electron from the styryl moiety of phosphite 9, rather than from phosphorus, and the detectability of 10 arise from the stabilizing effect of the 4-methoxy substituent. These results, however, do not allow conclusions to be made concerning the site of removal of an electron in the SET-induced photorearrangement of dimethyl 2-phenylallyl phosphite 1 to phosphonate 6.     

Green synthesis and bioactivity of 2-amino-4H-chromen-4-yl-phosphonates

A simple and efficient one pot synthesis of 2-amino-4H-chromen-4-yl phosphonate derivatives has been accomplished by the condensation of salicylaldehyde, malononitrile/ethylcyanoacetate and triethyl phosphite/trimethyl phosphite in the presence of molecular iodine as catalyst in water at room temperature. All the reactions were very clean and the products were obtained in very good to excellent yields. The title compounds are characterized by IR, 1H-, 13C-, 31P-NMR and mass spectra, also studied their antimicrobial and antioxidant activity.     

Unexpected course of rearrangement of substituted S-(1(3H)-isobenzofuranone-3-yl)isothiuronium bromides

Three series of S-(1(3H)-isobenzofuranone-3-yl)isothiuronium bromides differing in substitution at the isothiuronium moiety (none, one or two methyl groups) and at the benzene ring were prepared and characterized. These salts were then treated with various bases (acetate, triethylamine, Na₂CO₃) to give either 1-hydroxy-3-oxo-1,3-dihydro-2H-isoindol-2-carbothioamides or the product of S to N isobenzofuranone-3-yl migration, i.e., 1,3-dimethyl-1-(3-oxo-1,3-dihydro-2-benzofuran-1-yl)thioureas. If ammonia was used in reaction with N,N′-dimethyl isothiuronium salts then 3-hydroxy-2,3-dihydro-1H-isoindol-1-ones were formed together with 1,3-dimethyl-1-(3-oxo-1,3-dihydro-2-benzofuran-1-yl)thioureas in parallel reaction with the yields increasing with ammonia concentration. The formation of isoindolones takes place in two steps with an aldehyde intermediate, which can be trapped with N,N-dimethylhydrazine.     

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.     

Tributylphosphine Catalyzed O -Vinylation of 3-Hydroxy-2-methyl-4 H -pyran-4-one

Protonation of the highly reactive 1:1 intermediates produced in the reaction between tributylphosphine and dimethyl acetylenedicarboxylate by 3-hydroxy-2-methyl-4 H -pyran-4-one leads to vinyltributylphosphonium salts, which undergo an addition-elimination reaction in CH 2 Cl 2 at room temperature to produce dimethyl 2-[(2-methyl-4-oxo-4 H -pyran-3-yl)oxy]-2-butenedioate (1:1 mixtures of E and Z isomers) in fairly good yields.     

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.     

Interaction entre les phosphites alcoylés et le groupe carbonyle; trransformation des phosphites méthyliques dans l'acide acétique

In acetic acid, trimethyl phosphite dealkylates and simultaneously forms dimethyl (1-dimethoxyphosphono-ethyl) phosphate. This is interpreted as evidence of an attack at the carbonyl group of the carboxylic acid.     

Products in the Reactions of Trialkyl Phosphites with α-Halogeno-acetophenones in Alcoholic Media

Abstract

α-Hydroxyphosphonates are formed, in addition to vinyl phosphates and dehalogenated ketones, in the reactions of trimethyl phosphite (in methanol) or triethyl phosphite (in ethanol) with variously substituted α-chloro, α-bromo, and α,α,-dichloro-acetophenones. Tri-isopropyl phosphite in propan-2-ol gives only the vinyl phosphate. Ketophosphonates are not detectable amongst the reaction products under the conditions used. Trends in product composition can be correlated with the leaving ability of halogen, substituent effects, structure of the phosphite, and reaction temperature. Reactant ratios may also influence the product composition. The reactions of trimethyl phosphite in methanol with 4-nitro-α-chloroacetophenone, or α,α-dichloroacetophenones yield the dehalogenated α-hydrogxyphosphonates in addition. In the case of the 4-nitro derivative, this product cannot be accounted for by reaction of the phosphite with dehalogenated ketone (4-nitroacetophenone). Dehalogenation of the first-formed α-hydroxyphosphonate was, however, shown to occur under reaction conditions and appears to require the removal of positive chlorine, followed by protonation. Reactions of the α,α-dichloroacetophenones were similar to those of the α-chloroacetophenones, giving the corresponding chlorovinyl phosphate, α,α-dichloro-α-hydroxyphosphonate, and monodehalogenated ketone(i.e. α-chloroacetophenone); the latter was not however detected as it reacted further with excess phosphite to give the expected products as described above. Possible mechanisms for the various reactions are discussed. The ¹H and ¹³C nmr spectra of the α-hydroxy-phosphonates show magnetic non-equivalence of the two alkoxy groups, attributed to restricted rotation about the P-C bond as a result of intramolecular hydrogen-bonding.     

A New Protocol for O-Methylation of Phenolic Compounds with Trimethyl Phosphite or Trimethyl Phosphate Under Solvent-Free Condition and Microwave Irradiation

A simple method for the preparation of industrially important alkyl aryl ethers is reported. Several phenolic compounds such as phenols, naphthols, and hydroxy coumarins were O-methylated with trimethyl phosphite or trimethyl phosphate under microwave irradiation and solvent-free condition in almost quantitative yields. Reaction of 2-naphthol with trimethyl phosphate gave mixture of 2-methoxynaphthalene and 1-methyl-2-methoxynaphthalene while the reaction with trimethyl phosphite gave mostly 2-methoxynaphthalene. This method is highly efficient for the methylating of phenolic compounds with very easy experimental procedure and environmental friendly conditions.     

Lithiation of 1-alkyl-1H-1,2,4-triazol-5-yl phosphonic acid esters: Novel anion-mediated carbon-to-carbon phosphonate migrations

The lithiation chemistry of 1-alkyl-1H-1,2,4-triazol-5-yl phosphonic acid esters 3 has been investigated. Lithiation occurs exclusively on the 1-alkyl group, α to nitrogen, to give carbanionic intermediates 10 . No evidence was found for any lithiation at the 3-position of the triazole ring. On warming, intermediates 10 undergo an unusual anion-mediated phosphonate migration, giving rise to 1H-1,2,4-triazol-1-yl-methylphos-phonates 14 .