Reaction Pathways upon Interaction of Allenic Phosphonates with Selenyl Chlorides

Abstract

Studies were performed on the reaction between alkyl- and arylselenyl chlorides with esters of allenic phosphonic acids, variously substituted at their terminal C-atom. With the esters of the C-3 diasubstituted acids the reaction is highly regioselective and only oxaphosphol heterocyclization occurs to 2,5-dihydro-1,2-oxaphosphols 21-e. With the esters of the propadiene phosphonic acid the reaction is regio- and (Z)-stereoselective: only the 2,3-adducts 3a-b are formed, where the (Z)-isomer and the allenic phosphonates 4a-b are prevalent, as a result of 1,3-sigmatropic isomerization of 3a-b. With the esters of the C-3 monosubstituted acids, complex reaction mixtures are formed. From them were isolated: (E)- and (Z)-isomers of 2,5-dihydro-1,2-oxaphosphols 2f-j; (E)-and (Z)-isomers of the 2,3-adducts 3c-h; (E)-and (Z)-isomers of 4c-f; and (E)-and (Z)-isomers of the 1,2-adducts 5a-d. The reaction partially loses its regioselectivity, but the (Z)-stereoselectivity is preserved:     

The Hydrolysis of Phosphinates and Phosphonates: A Review

Phosphinic and phosphonic acids are useful intermediates and biologically active compounds which may be prepared from their esters, phosphinates and phosphonates, respectively, by hydrolysis or dealkylation. The hydrolysis may take place both under acidic and basic conditions, but the C-O bond may also be cleaved by trimethylsilyl halides. The hydrolysis of P-esters is a challenging task because, in most cases, the optimized reaction conditions have not yet been explored. Despite the importance of the hydrolysis of P-esters, this field has not yet been fully surveyed. In order to fill this gap, examples of acidic and alkaline hydrolysis, as well as the dealkylation of phosphinates and phosphonates, are summarized in this review.     

Synthesis of Substituted Phosphonates and Their Reactions with Carbonyl Compounds

Abstract

The reaction of the derivatives of 3-phenyl-3-chloro-2-oxopropionic acid with the trivalent phosphorus compounds has been studied. The esterification or amidation of this acid have been shown to influence the course of reaction with Ph₃P. In the reaction with esters enolphosphonium salts are produced, ketophosphonium salts are obtained when amides are involved. Properties of these compounds have also been studied in the Wittig reaction. 3-(α-chlorobenzyl)-2-oxoquinoxaline which reacted with trialkyl phosphates (Arbuzov reaction) has been synthesized. These phosphonates are obtained in nearly quantitative yields, in alkaline conditions (Horner-Emmons reaction) they react smoothly with aromatic aldehydes to give the substituted vinylyuinoxalines.     

Spontaneous Aromatization of Diels-Alder Adducts in the Reaction of Alkatrienyl Phosphonates with Alkyl Esters of Acetylencarboxylic Acids

Abstract

The subject of this study was the Diels-Alder reaction involving dialkyl (3-methylpenta-1,2,4-trienyl)phosphonates1a-d, dialkyl(5-methyl-hexa-1,3,4-trienyl)phosphonates 2a-b, and dienophiles (esters of acetylencarboxylic acids) 3a-c, at 65–90°C, in chloroform or with no solvent. The reaction between 1a-d and 3a-b led to the benzyl phosphonates 4a-h, while with 3c it proceeds to a mixture of 5a-d (90%) and 6a-d (10%), which are dialkyl esters of the 3-carboalkoxy(or 2-carboalkoxy)-6-methyl-benzyl phosphonic acid. The intermediate Diels-Alder adducts (A) are not even spectroscopically observable, i.e. in the course of the reaction a 1,5-sigmatropic isomerization occurs, accompanied by aromatization of (A). The isomerization is spontaneous: at ambient temperature 1a-d and 3a-b react slowly and form aromatic compounds:     

A novel and convenient method for synthesis of carbamoyl and thiocarbamoyl phosphonates

A simple, efficient, and general method has been developed for the synthesis of carbamoyl and thiocarbamoyl phosphonic esters using CaCl₂ as an efficient Lewis base catalyst. Carbamoyl and thiocarbamoyl phosphonic esters were obtained in good yield (37%–65%) and purity under mild conditions by the reaction of diethyl phosphite with isocyanates and isothiocyanates in the presence of CaCl₂. This method is easy, rapid, and good‐yielding reaction for the synthesis of carbamoyl and thiocarbamoyl phosphonic esters. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:250–253, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20538     

Synthesis of o-Carboranyl Containing Esters of Pentavalent Phosphorus Acids

Abstract

A new method for the synthesis of o-carboranyl containing phosphoric, phosphonic and phosphinic acid esters, where the o-carboranil group is in the ester group, has been developed. The propargyl esters of these acids were prapared in two ways: by the reaction of phosphorus acid salts with propargyl chlorid and by interaction of propargyl alcohol with acid chlorides in the presence of Et₃N. The propargyl esters have been converted into carboranyl containing compounds upon treatment with decaborane and dimethyl aniline     

New Applications of the Lithiated Phosphinimine Ph3P=N-Li: Synthesis of α,β-Unsaturated Nitriles and P=N-P Linked Phosphinimines

Abstract

The reaction of Ph₃P-N-Li⁽¹²⁾ with various α,β-unsaturated esters gives access to new N-(α,β-unsaturated acyl) phosphinimines. which can undergo intramolecular aza-Wittig reaction (at 65 - 110°C) to afford the corresponding nitriles.     

Electrochemical Properties of Ru Polypyridyl Phosphonates

[Ru(bpyPO₃H₂)(bpy)Cl]Cl (bpyPO₃H₂=6,6’-bipyridin-2-yl)phosphonic acid) and [Ru(tpy)(MepyPO₃H₂)Cl]Cl (MepyPO₃H₂=(pyridin-2-ylmethyl)phosphonic acid) were synthesized and characterized spectroscopically and electrochemically. Each compound was found to exhibit proton-coupled electron transfer (PCET). In the case of [Ru(bpyPO₃H₂)(bpy)Cl]Cl, a Ru(V/IV) couple was detected at 1.4 V vs. NHE. Each complex was tested for its ability to catalyze C−H bond oxidation using a variety of sacrificial oxidants, and it was found that under aqueous conditions [Ru(bpyPO₃H₂)(bpy)Cl]Cl oxidizes secondary C−H bonds using sodium periodate (NaIO₄) as the primary oxidant.     

Synthesis of New Porphyrin-Containing Peptidyl Phosphonates

Synthesis of new, porphyrin-containing peptidyl aminophosphonates is described. The products, derived from 5-(4′-carboxyphenyl)-10,15,20-tri-p-tolylporphyrin and some heterocyclic aminophosphonates were obtained in high yield in the reaction of the 5-(4′-carboxyphenyl)-10,15,20-tritolylporphyrin with selected thiophene and pyridine aminophosphonate diphenyl esters by applying a DCC coupling method used in the peptide synthesis. The obtained porphyrin aminophosphonate products were characterized by spectroscopic methods.     

Trimethylsilyl and Trimethylstannyl Esters of Trithiophosphonic Acid,Starting Compounds for the Synthesis of S-P-Heterocycles

Abstract

The silyl and stannyl esters of trithiophosphonic acids RP(S)(SEMe₃)₂ (E=Si, Sn; R=Me, t-Bu) are formed in high yield from the corresponding phosphanes RP(EMe₃)₂ by the addition of three sulfur atoms (3/8 S₈). The stannyl esters can also be obtained from the silyl esters and SnMe₃Cl or by reacting dithio=phosphonic acid anhydrides [RP(S)S]₂ with (SnMe₃)₂S. As a result of the pre=formed P-S-bonds and the reactivity of the S-E-bond towards Cl₂, Br₂ as well as chlorosulfanes S_xCl₂, the esters represent ideal starting compounds for the synthesis of sulfur-phosphorus-heterocycles of general formulas A and B. The tetrathiadiphosphorinanes [RP(S)S₂]₂, the products of the reaction with the halogens, are also formed in excellent yield when the silyl esters are treated with dimethylsulfoxide.     

Phase-Transfer-Catalyzed Michaelis-Becker Synthesis of Dialkyl Methyl Phosphonates

A liquid–liquid phase-transfer-catalyzed (PTC) Michaelis-Becker reaction was adopted in the preparation of dialkyl methyl phosphonate (R = Me, iPr, nBu, and iBu). This was performed by the reaction of an appropriate dialkyl hydrogen phosphonate with methyl iodide in the presence of benzyl triethyl ammonium chloride and sodium hydroxide as PTC and base, respectively. A liquid–liquid two-phase system (H₂O/CH₂Cl₂) introduced a suitable situation for the preparation of dialkyl methyl phosphonates with bulky alkyl groups (R = iPr, nBu, and iBu), but with R = Me, the hydrolysis of dimethyl hydrogen phosphonate (reagent) reduced the yield to 22%. In this case, a solid–liquid PTC-free system was successfully applied and yield of over 80% was obtained.     

Über eine Reaktion von o-Hydroxybenzylalkoholen mit Estern von Säuren des Phosphors mit der Koordinationszahl 3

Abstract

o-Hydroxybenzyl alcohol reacts with trimethyl phosphite under smooth conditions to o-hydroxyphenylmethane phosphonic acid dimethyl ester. This unusual reaction is of widest applicability. Derivatives of o-hydroxybenzyl alcohol independent of type, number or position of substituents in the ring, react with alkyl esters of phosphorous, phosphonous or phosphinous acids in an analogous process, forming the corresponding o-hydroxyphenylmethane phosphonic or phosphinic esters or phosphine oxides.     

Acids and their functionally substituted esters fromAmaranthus cruentus seed oil

The acid composition of seed oil ofAmaranthus cruentus and the synthesis of their glycidyl and pyridinecontaining esters are studied. It is demonstrated that 67% of the total acids are C₁₈-polyunsaturated linoleic and linolenic. A new method for preparing glycidyl esters of C₁₈-unsaturated carboxylic acids is developed by reacting their salts with ECG in an aprotic medium to produce the corresponding glycidyl esters. The reaction of the glycidyl esters and pyridine salts with carboxylic and phosphonic acids produces the propanolpyridine esters of the acids that combine the properties of the acids and pyridinium salts and are promising in the search for biologically active compounds.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 217–219, May–June, 2000.     

A density functional theory study of the stereoselectivity of Cu(OTf)2-catalyzed [3+2] cycloaddition of trifluoromethylated N-acylhydrazones and isoprene: A concerted asynchronous mechanism

Here we employ density functional theory calculations to systematically investigate the underlying mechanism of Cu(OTf)₂-catalyzed [3+2] cycloaddition reactions in the synthesis of CF₃-substituted pyrazolidines. About eight possible initial configurations of the [3+2] reaction is considered, and all relevant reactants, transition states, and products are optimized. Based on these structures, internal reaction coordinate paths, and wavefunction analysis results, we conclude that the Cu(OTf)₂-catalyzed [3+2] cycloaddition follows a concerted asynchronous mechanism. The C N bond forms immediately after the formation of the C C bond. Among the eight reaction paths, the energy barrier for the [3+2] reaction that leads to the CF₃-substituted syn-pyrazolidine is the lowest, ∼5.4 kcal/mol, which might result in the diastereoselectivity that is observed in the experiment. This work not only gives the detailed mechanism of the Cu(OTf)₂-catalyzed [3+2] cycloaddition but can also be helpful for the future designation of Cu(OTf)₂-based cycloaddition processes.     

Phosphorus-containing oligoamides obtained by a novel one-pot degradation of polyamide-6

This paper describes a novel strategy for the recycling of polyamide materials and their transformation into functional reactive oligomers with new properties. The method is illustrated by the heating of polyamide-6 (20,000 Da) in the presence of diesters of the phosphonic acid, (RO)₂P(O)H, where R could be -CH₃, -C₂H₅ or -C₆H₅. It is found that the reaction proceeds in several parallel processes: (i) phosphorylation of the amide group by the alkyl esters of the phosphonic acids and (ii) degradation of the main chain through an exchange reaction between the amide and phosphonic acid ester groups. Alternatively the depolymerization could be induced via a radical reaction with the participation of the polyamide moieties and the P-H group. The proceeding of the abovementioned reactions and the structure of the phosphorus-containing oligoamides are confirmed by ³¹P, ¹H and ¹³C NMR spectroscopy. Their molecular weights are determined by size exclusion chromatography.     

Reactions of diazo esters with electron-deficient alkenes in the presence of Lewis acids

1,3-Dipolar cycloaddition reaction of diazo esters to electron-deficient dipolarophiles to yield the corresponding 1- or 2-pyrazolines was found to be significantly accelerated with Lewis acids (Yb(OTf)₃, Sc(OTf)₃, GaCl₃, EtAlCl₂). The use of GaCl₃ as the catalyst leads to the acceleration not only of the 1,3-dipolar cycloaddition reaction, but also subsequent insertion of the CHCO₂Me electrophilic fragment of methyl diazoacetate into the N-H bond of 2-pyrazolines formed. Such Lewis acids as SnCl₄, BF₃, TiCl₄, and In(OTf)₃ are not efficient in the described processes, since they rapidly decompose starting diazo compounds.     

The influence of varying reaction conditions on the coordination behavior of the phosphonoformate anion

Abstract

In medical and pharmaceutical science phosphonic acids and phosphonates play an important role with regard to their wide application in various drugs as medicines against osteoporosis or antiviral agents. In the course of the investigations on the coordination chemistry of biologically active phosphonates different salts of the phosphonoformate anion were prepared via hydrolysis of corresponding esters under basic conditions. Depending on the reaction and crystallization conditions, different sodium salts with the phosphonoformate moiety were obtained and structurally characterized.     

P and H NMR studies of the transesterification polymerization of polyphosphonate oligomers

Polymeric phosphonate esters are an interesting class of organophosphorus polymers because both the polymer backbone and phosphorus substituents can be modified. These polymers have been prepared by ring-opening polymerizations of cyclic phosphites, stoichiometric polycondensations of dimethyl phosphonate with diols in conjunction with diazomethane treatment and by transesterification of polyphosphonate oligomers. Our initial attempts to prepare high molecular weight polymeric phosphonate esters by the transesterification methods were unsuccessful. Results indicate that the reactions of dimethyl phosphonate with diols to form polyphosphonate oligomers with only methyl phosphonate end groups are plagued by a serious side reaction that forms phosphonic acid end groups. These end groups do not participate in the transesterification reaction and limit the molecular weights of the polymers that can be obtained. The phosphonic acid end groups can be converted into reactive methyl phosphonate end groups by treatment with diazomethane, however diazomethane is explosive and the polymerization is slow. An alternative route for the production of high molecular weight polymers is the transesterification of the 1,12-bis(methyl phosphonato)dodecane, formed by the reaction of excess dimethyl phosphonate and 1,12-dodecanediol, with a Na₂CO₃ promoter. This allows polymers with molecular weights of up to 4.5×10⁴ to be prepared, and no phosphonic acid end groups are observed in these polymers. Thermal analyses of the poly(1,12-dodecamethylene phosphonate) have shown that this polymer has reasonable thermal stability (onset of thermal decomposition at 273 °C). This polymer also undergoes a cold crystallization process at 15 °C similar to that which has been observed in some polyesters, polyamides and elastomers.     

Comparison of Phosphonic and Pyrophosphonic Acids as Collectors for the Cassiterite Flotation

Abstract

Styryl phosphonic acid (SPA) is a collector used in the industrial flotation of cassiterite, During its production from styrene and PCl₅ by-products are formed in different amounts. One of these is condensed SPA caused by uncomplete hydrolysis of the intermediary phosphonic acid chloride. Attempts were made to synthesize definite forms of condensed SPA in order to study their influence on the results of flotation. Conventional methods-partial hydrolysis of phosphonic acid chlorides or reaction of acid chlorides with the free acid-did not lead to the desired result. Diammonium salt of the pyro-SPA was obtained by the method of (1) using dehydration of phosphonic acid by heating with urea. A series of analogous aromatic pyro-phosphonic acids was synthesized. The hydrophobization effect on Sn0₂ surfaces was studied by microflotation tests in a modified Hallimond tube. Pyrophosphonic acids are more hydrophobic than the corresponding phosphonic acids. The results of the microflotation experiments were confirmed by batch flotation tests with a natural tin ore in a 2–1 cell. The Sn recovery was higher with the pyro compounds.     

31P Sold-State NMR Investigations on Phosphonic Acids and Phosphonates

Abstract

As known from ³¹P solid-state NMR investigations of inorganic phosphates there is a correlation between chemical shift anisotropy parameters and crystal lattice parameters. For phosphonic acids and phosphonates similar correlations are not known.