An efficient Stille cross‐coupling reaction catalyzed by ortho‐palladated complex of tribenzylamine under microwave irradiation

The catalytic activity of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(μ‐Br)]₂ complex as an efficient, stable and catalyst that is non‐sensitive to air and moisture was investigated in the Stille cross‐coupling reaction of various aryl halides with phenyltributyltins under microwave irradiation. The substituted biaryls were produced in excellent yield in short reaction times using a catalytic amount of this complex in DMF at 100 C. The combination of dimeric complex as homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields in shorter reaction times. Copyright © 2011 John Wiley & Sons, Ltd.     

Understanding the efficacy of N,N-dimethylformamide and oxalyl chloride combination as chemoselective O-formylating agent: An unified experimental and theoretical study

We have developed a simple but efficient synthetic protocol for the O-formylation of a wide range of aromatic hydroxyl/phenolic substrates using an N,N-dimethylformamide (DMF) and oxalyl chloride [(COCl)₂] combination in dichloromethane (DCM) as solvent at ambient temperature. The DMF/(COCl)₂ combination was found to be highly chemoselective for the aromatic/phenolic hydroxyl group over aliphatic hydroxyl or aromatic amine/thiol groups. This chemoselectivity of DMF/(COCl)₂ combination towards O-formylation of aromatic alcohols was explained on the basis of outcomes of both experimental and density functional theory–based theoretical studies.     

Application of a dimeric ortho‐palladated complex of tribenzylamine as an efficient catalyst in microwave‐assisted Hiyama coupling reactions

The activity of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(μ‐Br)]₂ complex was investigated in cross‐coupling reactions of triethoxy(phenyl)silane with various aryl halides under microwave irradiation. This complex is an efficient and stable catalyst for the synthesis of substituted biphenyls that is non‐sensitive to air and moisture. The combination of dimeric complex as homogenous catalyst, microwave irradiation, DMF as microwave‐active polar solvent and TBAF as microwave‐active additive led to excellent yields in short reaction times. Copyright © 2012 John Wiley & Sons, Ltd.     

Efficient DMF‐Promoted Solventless Hydrolysis of Epoxides with Equimolar Amount of H2O,Affording 1,2‐Diols

A mild and efficient N,N‐dimethylformamide (DMF)–catalyzed solvent‐free hydrolysis of epoxides with an equimolar amount of H₂O to afford 1,2‐diols in good to excellent yields has been developed.     

NMR in chiral polypeptide liquid crystals: the problem of amines

It is shown that lyotropic liquid crystal mixtures made of poly-γ-benzyl-l-glutamate (PBLG) dissolved in N,N-dimethylformamide (DMF) are efficient anisotropic NMR solvents to distinguish the enantiomers of chiral amines through the effects of the differential ordering of enantiomers. This type of solvent overcomes problems often encountered when dissolving amines into the more conventional PBLG/CHCl₃ or PBLG/CH₂Cl₂ liquid crystals. Furthermore, it is shown that perdeuterobenzyl chloride is an excellent achiral deuterated derivatizing agent for enantiomeric excess measurements of chiral amines in conjunction with the PBLG/DMF solvent.     

(BeDABCO)2Pd2Cl6 (1‐benzyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane chloride) as a highly active catalytic system for the Stille cross‐coupling reaction under microwave irradiation

An efficient catalytic system using (BeDABCO)₂Pd₂Cl₆ was developed for the Stille cross‐coupling reaction. The substituted biaryls were produced in excellent yields in short reaction times using a catalytic amount of this catalyst in DMF at 120 °C. The ionic character of homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields and shorter reaction times than conventional heating. Benzyl DABCO as an efficient ligand and also a quaternary ammonium salt had an efficient stabilizing effect on the Pd(0) species. Copyright © 2013 John Wiley & Sons, Ltd.     

Pd(OAc)2/DABCO-catalyzed Suzuki-Miyaura cross-coupling reaction in DMF

The scope and limitations of the Pd(OAc)₂/DABCO (1,4-diaza-bicyclo[2.2.2]octane)-catalyzed Suzuki-Miyaura cross-coupling reactions have been demonstrated. The results showed that the effect of solvent had a fundamental influence on the reaction. In the presence of Pd(OAc)₂ and DABCO, both aryl bromides and aryl chlorides all worked well with arylboronic acids to form biaryls, heteroaryl-aryls, and biheteroaryls in moderate to excellent yields using DMF as the solvent. Additionally, the reactions of aryl bromides were conducted under relatively mild conditions.     

Enthalpies of Transfer of Tetraalkylammonium Bromides and CsBr from water to Aqueous DMF at 298.15 K

Enthalpies of transfer of tetraalkylammonium bromides and CsBr from water to aqueous DMF mixtures are reported and analyzed in terms of a new solvation theory. It was found that a previous equation could not reproduce these data over the whole range of solvent compositions. Using a new solvation theory to model the enthalpies of transfer shows excellent agreement between experimental and calculated values over the entire range of solvent compositions. The analyses show that tetrapropylammonium bromide, Pr₄NBr, and tetrapentylammonium bromide, Pen₄NBr, are preferentially solvated by water; in contrast tetrabutylammonium bromide, Bu₄NBr, is preferentially solvated by DMF. The solvation of tetramethylammonium bromide, Me₄NBr, and cesium bromide, CsBr, is random. The extent to which the tetraalkylammonium bromides disrupt solvent–solvent bonds increases systematically in going from Me₄NBr to Pen₄NBr.     

Poly(acrylonitrile) ultrafiltration membranes. I. Polymer‐salt‐solvent interactions

Fourier transform infrared spectroscopy was used to study the interactions among LiCl, ZnCl₂, and AlCl₃ with N,N‐dimethylformamide (DMF) and poly(acrylonitrile) (PAN). It was observed that all three salts complex with DMF as well as PAN. The strength of the cation interaction with the >C?O oxygen of DMF was found to be higher than that with the ? CN group of PAN. The >C?O stretching frequency of DMF with ZnCl₂ was red shifted, indicating stronger complex formation compared with other two cations. With the addition of salt, the salt–DMF pseudo solvent was found to become a θ solvent for PAN compared with neat DMF. This change in PAN solvation power was primarily the result of DMF–salt complexation. As a result of the complexation, Mark‐Houwink constant a, was found to reduce from 0.75 (for pure DMF) to ～0.6 for DMF–salt solvents, indicating decreased PAN chain expansion. Comparison of intrinsic viscosity [η] values indicated that addition of salts to PAN–DMF solutions resulted in: (i) decrease in the DMF solvation power, which causes less expanded polymer coils, and (ii) increased interpolymer chain entanglements via salt‐promoted chain association. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2061–2073, 2005     

Etude de la solvolyse des tosylates d'aryl-2 propyle dans le dimethylformamide

Aryl-2 propyltosylate solvolysis occurs in DMF as in a protic medium, via two competing mechanisms: solvent nucleophilic substitution (rate constant k_s) unimolecular solvolysis with aryl participation (k_Δ). Nucleophilic solvent participation is more important in DMF than in a protic solvent; this is due to the lack of electrophilic assistance of DMF compared to a hydroalcoholic solvent (k_Δ^DMF < k_Δ^{EtOH aq.}), DMF and aqueous carbon nucleophilicities being nearly the same (k_s^DMF ? k_s^{EtOH aq.}). Charge distribution in transition states are of the same type in both solvents.     

Solvent-assisted thiocarboxylation of amines and alcohols with carbon monoxide and sulfur under mild conditions

DMSO or DMF as a solvent strongly accelerated the thiocarboxylation of amines and alcohols with carbon monoxide and sulfur. Under mild conditions (1 atm, 20 °C), this thiocarboxylation of amines assisted by DMSO with carbon monoxide and sulfur has been developed into a practical and convenient synthetic method for S-alkyl thiocarbamates in good to excellent yields, including EPTC, thiobencarb, orbencarb, and molinate (herbicides). DMF also showed the similar solvent effect. NMP slightly decreased the effect for the thiocarboxylation of amines, and the yield of S-alkyl thiocarbamate was lowered in DMAc. Surprisingly, no formation of S-alkyl thiocarbamate was observed at the use of the other solvents, such as THF, hexane, toluene, AcOEt, MeCN, MeOH, and H₂O. The present solvent-assisted thiocarboxylation with carbon monoxide and sulfur could be also applied to a new synthesis of S-alkyl O-alkyl carbonothioates from alcohols under mild conditions (1 atm, 20 °C) in DMF using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene).     

Primary sulfonamide as a coupling partner: Copper(I)-catalyzed regioselective cross-coupling of 2-nitro benzenesulfonamides with thiol through the cleavage of Ar–SO2NH2 bonds

In this article, we have presented a novel and efficient method for the direct synthesis of unsymmetrical sulfides through the copper(I)-catalyzed cross-coupling of 2-nitro benzenesulfonamides with thiols in the presence of catalytic amount of CuI in DMF as solvent at 100?°C. In addition, the products were obtained in high to excellent yields. More importantly, the novel system showed the primary 2-nitro benzenesulfonamides as a new coupling partner and regioselectively promoted C–S bond-forming transformations through the cleavage of Ar–SO₂NH₂ bonds.     

Exchange of Coordinated Solvent During Crystallization of a Metal–Organic Framework Observed by In Situ High‐Energy X‐ray Diffraction

Using time‐resolved monochromatic high energy X‐ray diffraction, we present an in situ study of the solvothermal crystallisation of a new MOF [Yb₂(BDC)₃(DMF)₂]?H₂O (BDC=benzene‐1,4‐dicarboxylate and DMF=N,N‐dimethylformamide) under solvothermal conditions, from mixed water/DMF solvent. Analysis of high resolution powder patterns obtained reveals an evolution of lattice parameters and electron density during the crystallisation process and Rietveld analysis shows that this is due to a gradual topochemical replacement of coordinated solvent molecules. The water initially coordinated to Yb³⁺ is replaced by DMF as the reaction progresses.     

Cobalt(II) chloro complexation in N-methylformamide–N, N-dimethylformamide mixtures

Cobalt(II) chloro complexation has been studied by titration calorimetry and spectrophotometry in solvent mixtures of N-methylformamide (NMF) and N,N-dimethylformamide (DMF). It revealed that a series of mononuclear CoCln_n ^(2–n)+ (n=1–4) complexes are formed in the mixtures of NMF mole fraction x _NMF=0.05 and 0.25, and the CoCl⁺, CoCl₃ ^– and CoCl₄ ^2– complexes in the mixture of x _NMF=0.5, and their formation constants, enthalpies and entropies were obtained. As compared with DMF, the complexation is markedly suppressed in the mixtures, as well as in NMF. The decreasing formation constant of CoCl⁺ with the NMF content is mainly ascribed to the decreasing formation entropy. DMF is aprotic and thus less-structured, whereas NMF is protic to form hydrogen- bonded clusters. In DMF-NMF mixtures, solvent clusters in neat NMF are ruptured to yield new clusters involving DMF, the structure of which depends on the solvent composition. The entropy of formation of CoCl⁺ will be discussed in relation to the liquid structure of DMF, NMF and their mixtures.     

Solvent Effect on the Separation Mechanism in HPGPC of Polyimide and Polyethersulfone

Abstract

Molecular weight distributions (MWD) of polyethersulfone (PES) and various polyimides (PI) in dimethyl formamide (DMF), dimethyl acetamide (DMAc), methylene chloride (MeCl2) and 0.05 M LiBr in DMF were determined using a set of Ultrastyrogel® columns of nominal porosity 10³, 10⁴, 10⁵and 10⁶A?. The resulting chromatograms were bimodal or mukimodal in DMF or DMAc and thus are not useful for reliable determinations of MWD. MeCl₂ gave unimodal chromatograms but because of its low boiling point, this solvent is not recommended for use at or above room temperature. MWD determinations in 0.05 M LiBr in DMF also gave unimodai chromatograms and can be used for reliable MWD determinations in combination with light scattering measurements.     

MORPHOLOGICAL TRANSITION BETWEEN VESICLES AND TUBULES FOR A GLYCOPOLYMER-CONTAINING AMPHIPHILIC DIBLOCK COPOLYMER IN AQUEOUS SOLUTIONS*

The morphological transition of molecular assemblies in aqueous solutions for a new amphiphilic diblockcopolymer induced by changing the initial solvent conditions was studied by transmission electron microscopy (TEM). Thecopolymer was polystyrene(77)-b-poly [2 -(β-D-glucopyranosyloxy) ethyl acrylate (6)] (PSt_(77)-b-PGEA_6) and the solvent was amixture of DMF and THF. PSt_(77)-b-PGEA_6 yields vesicles and tubules when it is initially dissolved in THF and DMFrespectively. The morphological transition between vesicles and tubules can be achieved by simply varying the amounts ofTHF and DMF, or changing the temperature at which the aggregates were prepared.     

Micellar behavior of a well-defined dendritic polymer (PS2PI)3: the effects of architecture and solvent selectivity

The micelles formed when a dendritic polymer of polystyrene (PS) and polyisoprene (PI), having the overall structure (PS₂PI)₃, were examined in two solvents, dimethylformamide (DMF) and dimethylacetamide (DMA). Both solvents are good solvents for polystyrene and non-solvents for polyisoprene. The aggregation behavior was studied by a combination of static and dynamic light scattering and viscometry. In both systems star-like micelles were formed which followed the hard sphere model. The aggregation number was much lower for the micelles formed in DMA. The polymer-solvent interaction parameters indicate that the interactions are stronger between both PS-DMA and PI-DMA than for either polymer block with DMF. The effects of solvent selectivity are exacerbated by the structure of the polymer. With each polymer molecule contributing six soluble arms to the micelle, in the better solvent (DMA) increased repulsive interactions between the extended polystyrene lead to lower aggregation numbers.     

Synthesis and Characterization of Some N-Aryl-4-nitroimidazoles as Potential Insensitive Energy Materials

N‐Aryl derivatives of 4‐nitroimidazole have been synthesized under CuI/TBAB catalytic system in excellent yields, using KOH as base in DMF solvent.     

Efficient and Practical Route to α‐Aminocarbonylketene and α‐Cyanoketene Dithioacetals

An efficient and practical route to α‐aminocarbonylketene dithioacetals 5 and α‐cyanoketene dithioacetals 6 was developed. With readily available α‐acetyl‐α‐aminocarbonyl ketene dithioacetals 4 as the starting materials, α‐aminocarbonylketene dithioacetals 5 were prepared in high yield via base‐catalyzed (sodium hydroxide) deacetylation. In the presence of POCl₃ and with DMF as the solvent, α‐cyanoketene dithioacetals 6 were obtained via dehydration of 5 in excellent yield.     

Copper-based reverse ATRP process of styrene in mixed solvents

Xylene/N,N-dimethylformamide (DMF) and xylene/ethanol were employed as mixed solvents, respectively, for the reverse atom transfer radical polymerization (R-ATRP) of styrene with the azobisisobutyronitrile (AIBN)/CuBr₂/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) initiating system. With a limited amount of DMF added in, CuBr₂/PMDETA complex could dissolve well in the reaction system, so the control of polymerization was enhanced compared with the one in which simplex xylene was used as solvent. But the polarity of DMF leaded kinetics to deviation from first order. Ethanol could also improve the solubility of catalyst and be scavenged quickly by argon at 110°, therefore the impact of polarity of solvent on kinetics was negligible. Induction periods were not observed here indicating rapidly establishment of equilibrium between Cu(I) and Cu(II). This method that adding a little amount of polar solvent with low boiling point into non-polar solvent gives a new way to solve the problem of poor solubility of the catalyst in R-ATRP.