Formylation of alkyl cyanofurylmethanphosphonates at the active methylene group

Alkyl cyanofurylmethanephosphonates are formylated with ethyl formate in the presence of sodium foil to form sodium derivatives of phosphonoacetic aldehyde. If phosphonoacetic aldehyde and nitrile groups occupy remote positions in the furan ring, the sodium derivative in DMSO solution exists in the form of carbanion carrying charge on the carbon atom adjacent to the aldehyde group. If the substituents are located at the adjacent carbons of furan ring, the solution equilibrium between the carbanionic (major product) and Z-enolate forms of salts is established. Alkylation of the formed salts with methyl iodide occurs exclusively at the oxygen atom to give methyl enolates. In most cases, a mixture of E-and Z-isomers is formed, the E one being prevailing. In the case of 2,5-location of the substituents in furan ring, the sodium salt is inactive, and the alkylation does not occur.     

Reaction of 2- and 3-furylmethanephosphonates with esters

2- and 3-furylmethanephosphonates are acylated with ethyl formate, diethyl oxalate, and ethyl trifluoroacetate in toluene in the presence of sodium foil to afford five phosphorylated derivatives of furylacetic aldehyde, furylpyruvic acid, and 1,1,1-trifluoro-1-(2-furyl)propan-2-one. In a chloroform solution these compounds exist in the equilibrium with their enolic forms. When treated with sodium ethylate they form sodium salts which were isolated and characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy. It was shown that in DMSO solutions sodium salts of formyl and oxalyl derivatives of 2-furylmethanephosphonate exist as mixtures of the carbanion and enolate forms. In the first case the carbanion form is predominant, while in the second one the enolate forms prevail. Sodium salt of formylated 3-furylmetanephosphonate exists only in the carbanion form, while the salt of 3-furylpyruvate is enolate. The alkylation of these salts with iodomethane proceeds at the carbon atom as well as at the oxygen one. First reaction pathway is often preferred.     

Reaction of (ethoxycarbonylfuryl)methanephosphonates with diethyl carbonate in presence of sodium foil

Reaction of (ethoxycarbonylfuryl)methanephosphonates with diethyl carbonate in presence of sodium foil is studied. It is shown that if the acidifying group is conjugated with the carbanion center of 2-furylmethanephosphonate, addition of the carbanion to the carbonyl group of diethyl carbonate takes place to give 2-furylacetic acid derivatives in high yield. Sodium salts of these CH-acids are synthesized, isolated, and characterized. Their alkylation with alkyl bromoacetates is carried out. If ethoxycarbonyl group is not conjugated with the carbanion center, conversion of starting phosphonate and yield of adduct sharply decreases. Alkyl (2- and 4-ethoxycarbonylfur-3-yl)methanephosphonates immediately after acylation with diethyl carbonate are reduced with sodium-diethyl carbonate system to form alkyl 1-(2- and 4-ethoxycarbonylfur-3-yl)-ethanephosphonates. Formation of intermediate reduction product, the phosphorylated furylacetic aldehyde is also fixed spectroscopically. Simultaneously with the reduction dealkylation of ester group of starting phosphonates and alkyl 1-(3-furyl)ethanephosphonates takes place leading to the carboxylic acid salts. Alkyl (2-methyl-5-ethoxycarbonylfur-3-yl)methanephosphonate does not take part in condensation. It gives only the products of dealkylation under the action of sodium ethylate forming from diethyl carbonate.     

Cross-coupling of organoboronic acids and sulfinate salts using catalytic copper(II) acetate and 1,10-phenanthroline: synthesis of aryl and alkenylsulfones

A mild method for the preparation of aryl and alkenylsulfones from the cross-coupling reaction of organoboronic acids and sodium sulfinate salts is described. Optimized conditions utilize a catalytic amount of copper(II) acetate monohydrate with 1,10-phenanthroline as ligand in the presence of 4 Å molecular sieves. A co-solvent mixture of dichloromethane/DMSO was used, with reactions occurring at 40 °C under an atmosphere of oxygen. Reaction at room temperature also yields sulfone product, but in lower yields. The method tolerates a variety of substituents on the organoboronic acid, including amide, aldehyde, halide and nitro functionalities, as well as ortho-substituents. In general, the reaction is found to be less efficient using arylboronic acids bearing electron-withdrawing substituents, or using aryltrifluoroborate salts.     

Alkylation of Diethylphosphonoacetic Aldehyde and Triethyl Phosphonoacetate with Ethyl α-Bromopropanoate

Russian Journal of General Chemistry - The alkylation reactions of phosphonoacetic aldehyde and ethyl phosphonoacetate with ethyl α-bromopropanoate in DMSO in the presence of K2CO3 have been...     

Synthesis of (η-arene)(η-cyclopentadienyl) iron (II) complexes with heteroatom and carbonyl substituents. Part I: Oxygen and carbonyl substituents

A series of reactions have been used to introduce oxygen substituents into (η-arene)(η-cyclopentadienyl) iron (II) complexes. Photochemical ligand exchange led to the formation of the first recorded trioxygenated complex as well as mono- and di-oxygenated species. Using microwave techniques, reaction times for S_NAr displacement reactions of halobenzene complexes by phenols were reduced from several hours to a few minutes. Phenols protected by either t-butylation or trimethylsilylation were found to give modest yields of the corresponding phenol complexes, using conventional thermal ligand exchange reactions. Without such protection, yields were extremely low. The above method led to the synthesis of the first example of a dihydroxybenzene complex. Some miscellaneous syntheses are also reported.The Nef reaction has been adapted to convert (η⁶-α-nitroalkylarene)(η⁵-Cp) iron (II) salts to corresponding aldehyde and ketone complexes. The α-nitroalkyl arene complexes were synthesised in good yields from (η⁶-halobenzene)(η⁵-Cp) iron (II) complexes using NaOtBu in DMSO. H/D exchange reactions with ²[H]₆-DMSO in the presence of K₂CO₃ showed partial D incorporation in the methyl group for the unreacted α-nitroethylbenzene complex and complete exchange for the carbanion generated by deprotonation. Conversion of the α-nitroalkylarene complexes to the corresponding aldehyde and ketone complexes was accomplished in moderate yields using three methods:

(A)

H₂O₂ and NaOtBu in DMSO followed by reaction with CF₃CO₂H.

(B)

SnCl₂/aq. HCl.

(C)

K₂CO₃ in DMF using microwave-mediated reactions.

In addition, two one-pot syntheses are reported using methods B and C.     

Theoretical study on structural and mechanistic aspects of synthesis of a 3-aminopyrazole derivative

The structure of 5-hydroxy-3,5-dimethyl-1-S-methylisothiocarbamoyl-2-pyrazolinium iodide (HDMCPI), a cyclic intermediate for a 3-aminopyrazole derivative, was determined by means of X-ray analysis and spectroscopic techniques. In a treatment of HDMCPI in alkaline aqueous solution, 4-acetyl-3(5)-amino-5(3)-methylpyrazole (AAMP) was unexpectedly yielded. The reaction of HDMCPI was monitored by ¹H and ¹³C NMR spectroscopy. It was shown that keto-imine tautomer appears as the only tautomeric form. Density functional theory explained the spontaneous formation of keto-imine tautomer, whose existence is the main condition for generating a carbanion in alkaline medium. The carbanion further undergoes cyclization and elimination of MeSH, thus yielding AAMP. In the reaction of acetylacetone with thiosemicarbazide instead of S-methylisothiosemicarbazide, there were no traces of AAMP. This result can be attributed to the absence of keto-imine form in the tautomeric equilibrium, which would provide the formation of a carbanion for a nucleophilic attack and further cyclization.     

One-pot synthesis of 2-substituted thieno[3,2-b]indoles from 3-aminothiophene-2-carboxylates through in situ generated 3-aminothiophenes

A convenient protocol for one-pot synthesis of thieno[3,2-b]indoles, bearing aromatic, thien-2-yl or styryl fragments at C-2 position, from easily accessible 5-substituted 3-aminothiophene-2-carboxylates using the Fischer indolization reaction, was developed during this study. Two main steps of this approach are the saponification of the starting 3-aminoesters with sodium hydroxide and next treatment of the crude 3-aminoacids sodium salts with arylhydrazines in glacial acetic acid solution. The latter step includes in situ decarboxylation of the freed 3-aminothiophene-2-caboxylic acids to the 3-aminothiophenes and their acid promoted reaction with arylhydrazines to initially form arylhydrazones of 5-substituted thiophene-3(2H)-ones, which smoothly cause indolization to afford the desired thieno[3,2-b]indoles.     

New protic salts of aprotic polar solvents

Aprotic polar solvents such as DMF, acetonitrile or DMSO can be protonated to form stable triflate salts when treated with triflic acid. The reaction of the same solvents with N,N-bis(trifluoromethanesulfonyl)imide led to the isolation of the corresponding N,N-bis(trifluoromethanesulfonyl)imide salts.     

Protonated arginine and lysine as catalysts for the direct asymmetric aldol reaction in ionic liquids

Side chain protonation of basic α-amino acids with Brønsted acids provides new effective catalysts for the direct asymmetric aldol reaction of cyclic ketones with aromatic aldehydes in ionic liquids and DMSO. Increased yields are obtained in N-butyl N-methyl pyrrolidinium triflate ([bmpy][TfO]) with respect to DMSO using argininium tosylate (Arg·PTSA) as a 1.3 M aq solution in 10% molar amount with respect to the limiting aldehyde.     

Transition‐metal‐free Chemoselective Oxidative C−C Coupling of the sp3 C−H Bond of Oxindoles with Arenes and Addition to Alkene: Synthesis of 3‐Aryl Oxindoles,and Benzofuro‐ and Indoloindoles

A transition‐metal (TM)‐free and halogen‐free NaOt Bu‐mediated oxidative cross‐coupling between the sp³ C−H bond of oxindoles and sp² C−H bond of nitroarenes has been developed to access 3‐aryl substituted and 3,3‐aryldisubstituted oxindoles in DMSO at room temperature in a short time. Interestingly, the sp³ C−H bond of oxindoles could also react with styrene under TM‐free conditions for the practical synthesis of quaternary 3,3‐disubstituted oxindoles. The synthesized 3‐oxindoles have also been further transformed into advanced heterocycles, that is, benzofuroindoles, indoloindoles, and substituted indoles. Mechanistic experiments of the reaction suggests the formation of an anion intermediate from the sp³ C−H bond of oxindole by tert ‐butoxide base in DMSO. The addition of nitrobenzene to the in‐situ generated carbanion leads to the 3‐(nitrophenyl)oxindolyl carbanion in DMSO which is subsequently oxidized to 3‐(nitro‐aryl) oxindole by DMSO.     

Chimie des complexes de metaux de transition avec des hydrocarbures cyanes : III. Quelques observations sur la conformation et la reactivite de complexes dicyclopentadienyles du molybdene et du tungstene

A new class of cyclic telluronium salts has been prepared. All the salts are stable in solution in CHCl₃ or dimethylsulphoxide (DMSO). Conductivity measurements in DMSO and dimethylformamide (DMF) have shown that considerable ion pairing occurs in solution. Infrared, ¹H, ¹³C, ¹²⁵Te NMR, and mass spectra are reported and discussed.     

<Emphasis Type="Italic">Ab initio</Emphasis> quantum-chemical study of the reaction mechanisms of acetylene in superbasic media. Noncatalytic vinylation of methanol

The reaction profile of noncatalytic vinylation of methanol with acetylene was studied by ab initio quantum-chemical calculations for the gas phase and by calculations using a combined model that took into account the solvent (DMSO) effect. The reaction occurs via the formation of a prereaction complex of the methoxide ion with acetylene; at this stage, the acetylene molecule is already activated with respect to the proton. The observed stereospecific trans-addition in methanol vinylation in the gas phase and solution is provided by the lower activation barrier corresponding to the E structure of the acetylene molecule in the transition state and barrier-free protonation of the carbanion intermediate.     

Dimethylplatinum(IV) compounds. V. Preparation and reations of bis(salicylaldehydato) complexes

Two geometrical isomers of Pt(CH₃)₂(Sal)₂ have been prepared and identified by ¹H NMR spectra. Some reactions of isomer A (phenolic oxygen atoms trans to CH₃) and isomer B (aldehydic oxygen atoms trans to CH₃) are reported. Isomer B reacts with C₅D₅N to produce species containing unidentate Sal in solution, while isomer A tends to lose Sal with formation of hydroxo species. Primary amines react with isomer B to form salicylaldimine complexes. Isomer A reacts with en to form Pt(CH₃)₂en(0H)₂.     

Conjugates of polyhedral boron compounds with carbohydrates 8. Synthesis and properties of nido-ortho-carborane glycoconjugates containing one to three ��-lactosylamine residues

??-Lactosylamine derivatives containing one to three disaccharide residues with the bromine atom at the terminal position of aglycon were synthesized. Conjugation of these derivatives with 1-mercapto-1,2-dicarba-closo-dodecaborane was carried out in DMSO, which was accompanied by deboronation to form nido-ortho-carborane (7,8-dicarba-nido-undecaborate) glycoconjugates in up to 70% yield. The hydrolytic stability of glycoconjugates and the binding efficiency of their triethylammonium salts to castor-bean galectin (Ricinus communis aggluinin, RCA₁₂₀) were estimated. Glycoconjugates are decomposed in an aqueous solution by ??15% at 37 °C in three days. The glycoconjugate salt with one ??-lactosylamine residue binds to galectin analogously to lactose; after indroduction of the second ??-lactosylamine residue into glycoconjugate, the binding efficiency increases ??6-fold due to the cluster effect.     

Quantification of Ion‐Pairing Effects on the Nucleophilic Reactivities of Benzoyl‐ and Phenyl‐Substituted Carbanions in Dimethylsulfoxide

Second‐order rate constants for the reactions of acceptor‐substituted phenacyl (PhCO?CH^??Acc) and benzyl anions (Ph?CH^??Acc) with diarylcarbenium ions and quinone methides (reference electrophiles) have been determined in dimethylsulfoxide (DMSO) solution at 20 °C. By studying the kinetics in the presence of variable concentrations of potassium, sodium and lithium salts (up to 10^?2 mol L^?1), the influence of ion‐pairing on the reaction rates was examined. As the concentration of K⁺ did not have any influence on the rate constants at carbanion concentrations in the range of 10^?4–10^?3 mol L^?1, the acquired rate constants could be assigned to the reactivities of the free carbanions. The counter ion effects increase, however, in the series K⁺<Na⁺<Li⁺, and the sensitivity of the carbanion reactivities toward variation of the counter ion strongly depends on the structure of the carbanions. The reactivity parameters N and s_N of the free carbanions were derived from the linear plots of log k₂ against the electrophilicity parameters E of the reference electrophiles, according to the linear‐free energy relationship log k₂(20 °C)=s_N(N+E). These reactivity parameters can be used to predict absolute rate constants for the reactions of these carbanions with other electrophiles of known E parameters.     

Raman spectra of chlorophyll forms

The Raman spectra of chlorophyll a (Chl) forms in aqueous poly(vinyl alcohol) (PVA) and in dimethyl sulfoxide (DMSO)—water mixtures were recorded at 457.9 nm excitation and their structures were characterized by comparison with the spectra of the following well-known chlorophyll forms: (1) monomers (Chl)₁ in the polar solvents of group (A), i.e., diethyl ether, tetrahydrofuran, acetone, N,N-dimethylformamide and DMSO, of which the oxygen atom is expected to coordinate to the central magnesium atom; (2) monomers (Chl)₁ in the polar solvents of group (B), i.e., methanol, ethanol, 1-propanol, 2-propanol and 1-butanol, which are supposed to form a hydrogen-bond to the C₉=O group in addition to the coordination-bond to the Mg atom; (3) dehydrated aggregates (Chl)_n in dry non-polar solvents, i.e., carbon tetrachloride, n-hexane and n-octane; and (4) hydrated aggregates (Chl·2H₂O)_n in wet non-polar solvents, i.e., n-hexane and n-octane. The frequency of the C₉ = O stretching Raman line of each of the above chlorophyll forms was: (1) 1702—1680 cm⁻¹; (2) 1673—1668 cm⁻¹; (3) around 1655 cm⁻¹; (4) around 1645 cm⁻¹. The frequency proved to be a marker of intermolecular interaction of the Chl molecules. The spectral patterns in the 1650—700 cm⁻¹ region of (1), (2) and (3) were similar. However, the relative intensities of Raman lines of (4), which was ascribed to a one-dimensional, regular stacking of the Chl macrocycles, were quite different from those of (1)—(3).The chlorophyll form in PVA aqueous solution was identified as (Chl·2H₂O)_n by spectral comparison. The chlorophyll forms present in the DMSO—water mixtures were highly dependent on the DMSO content. It is suggested that (Chl)₁ having hydrogen-bonded H₂O should be present in 10% DMSO solution, and that a new chlorophyll form (Chl·DMSO)_n having (a) a stoichiometric intermolecular interaction with DMSO and (b) a regular stacking of the chlorophyll macrocycles, should be predominant in 50% DMSO aqueous solution.     

Reactions of thioquinanthrene with sodium alkanethiolates. The smiles rearrangement of diquinolinyl sulfides

Reactions of thioquinanthrene 1 with sodium alkanethiolates or S-alkylisothiouronium salts (in the presence of sodium hydroxide) at 70° in DMSO or DMF yielded 4,4′-dialkylthio-3,3′-diquinolinyl sulfides 3 , which were results of the S-S type of the Smiles rearrangement of primary reaction products - sodium 3-quinoline-thiolates 6. When the reactions were carried out at 20° the products were 3′,4-dialkylthio-3,4′-diquinolinyl sulfides 2.     

Ring opening of pyridines: the pseudo‐cis and pseudo‐trans isomers of tetra‐n‐butylammonium 4‐nitro‐5‐oxo‐2‐pentenenitrilate

The reaction of 2‐chloro‐5‐nitropyridine with two equivalents of base produces the title carbanion as an intermediate in a ring‐opening/ring‐closing reaction. The crystal structures of the tetra‐n‐butylammonium salts of the intermediates, C₁₆H₃₆N⁺·C₅H₃N₂O₃⁻, revealed that pseudo‐cis and pseudo‐trans isomers are possible. One crystal structure displayed a mixture of the two isomers with approximately 90% pseudo‐cis geometry and confirms the structure predicted by the S_N(ANRORC) mechanism. The pseudo‐cis intermediate undergoes a slow isomerization over a period of months to the pseudo‐trans isomer, which does not have the appropriate geometry for the subsequent ring‐closing reaction. The structure of the pure pseudo‐trans isomer is also reported. In both isomers, the negative charge is highly delocalized, but relatively small differences in C—C bond distances indicate a system of conjugated double bonds with the nitro group bearing the negative charge. The packing of the two unit cells is very similar and largely determined by the interactions between the planar carbanion and the bulky tetrahedral cation.     

A one-pot synthesis and mild cleavage of 2-[2- or 5-(alkylsulfanyl)pyrrol-1-yl]ethyl vinyl ethers by t-BuOK/DMSO: a novel and facile approach to N-vinylpyrroles

Substituted N-[2-(vinyloxy)ethyl]pyrroles, prepared in good yield through an allenic or acetylenic carbanion/isothiocyanate one-pot methodology from 2-(vinyloxy)ethyl isothiocyanate and allyloxyallene, methoxyallene, N,N-dimethyl-2-propyn-1-amine, and 3-methoxy-1-(methylsulfanyl)-1-propyne, are smoothly converted into the corresponding N-vinylpyrroles using t-BuOK/DMSO (room temperature). The reaction proceeds via elimination of vinyl alcohol from the N-[2-(vinyloxy)ethyl] substituent and represents a novel approach to N-vinylpyrroles.