Polarity Of Reaction Medium Research Articles

Recent Advances in the Use of Dimethyl Sulfoxide as a Synthon in Organic Chemistry.

Dimethyl sulfoxide (DMSO), as extremely important aprotic polar solvent and reaction medium, has attracted widespread attention from chemists in recent years due to its wide range of uses and the multiple functions it displays in various chemical processes. Especially in the past decade, dimethyl sulfoxide has become increasingly favored as a synthon in organic chemistry, resulting in great progress in this research field. In this context, this review provides a comprehensive summary of the literature on the recent progress in organic synthesis using dimethyl sulfoxide as a synthon, covering all the reports from 1 January 2016 to 11 May 2022. This type of reaction is mainly performed by transferring one or more units of dimethyl sulfoxide, such as oxygen (-O-, =O), methyl (-CH3), methylene (-CH2-), methylidene (=CH2), methine (=CH-), donor of formylation (-CHO), sulfur (-S-), methylthio (-SMe), methyl sulfoxide (-SOMe), donor of methyl thiomethylation (-CH2SMe), or donor of methyl sulfoxide methylation (-CH2SOMe), to the target molecules. At the same time, we hope that this review will stimulate future studies and promote developments in this area.

Effect of solvent polarity in formation of perfectly ordered CMK-3 and CMK-5 carbon replicas by precipitation polycondensation of furfuryl alcohol

Two twin series of carbon replicas were synthesized by the acid-catalyzed precipitation polycondensation of various amounts of furfuryl alcohol in SBA-15 suspensions using water and toluene as reaction media. The textural and structural parameters, as well as the morphology of the polymer/silica carbonizates and corresponding replicas, were investigated comprehensively. It was found that the polarity of the reaction medium plays an essential role in the scenario of the deposition of poly(furfuryl alcohol) (PFA) onto the surface of the silica matrix. Namely, the water-based environment results in propagating PFA chains radially from the pore centres to the wall thereof, while in the case of toluene its growth progresses in the reverse direction. The spectroscopic studies disclosed that this is due to the competitive adsorption of monomer and solvent on the superficial silica silanol groups. In the case of the water-furfuryl alcohol system, H 2 O is adsorbed preferentially, hindering the formation of a homogenous polymer layer, thus precluding the formation of a hollow-type replica. Contrarily, for the toluene-furfuryl alcohol mixture, the monomer adsorption is favored. Furthermore, the forming polymer anchors to the silica surface covalently and clads it evenly, therefore facilitating the formation of a high-quality CMK-5 structure. • Two series of carbon replicas were cast from SBA-15 in H 2 O and toluene environments. • Polarity of reaction medium plays crucial role in the deposition of carbon precursor. • Competitive monomer vs. solvent adsorption onto surface of SBA-15 silanols was found. • In the case of the aqueous system, H 2 O molecules are adsorbed preferentially. • Favored monomer adsorption in toluene leads to obtain an excellent CMK-5 structure.

Insights into Elution of Anion Exchange Cartridges: Opening the Path toward Aliphatic 18F-Radiolabeling of Base-Sensitive Tracers.

Aliphatic nucleophilic substitution (SN2) with [18F]fluoride is the most widely applied method to prepare 18F-labeled positron emission tomography (PET) tracers. Strong basic conditions commonly used during 18F-labeling procedures inherently limit or prohibit labeling of base-sensitive scaffolds. The high basicity stems from the tradition to trap [18F]fluoride on anion exchange cartridges and elute it afterward with basic anions. This sequence is used to facilitate the transfer of [18F]fluoride from an aqueous to an aprotic organic, polar reaction medium, which is beneficial for SN2 reactions. Furthermore, this sequence also removes cationic radioactive contaminations from cyclotron-irradiated [18O]water from which [18F]fluoride is produced. In this study, we developed an efficient elution procedure resulting in low basicity that permits SN2 18F-labeling of base-sensitive scaffolds. Extensive screening of trapping and elution conditions (>1000 experiments) and studying their influence on the radiochemical yield (RCY) allowed us to identify a suitable procedure for this. Using this procedure, four PET tracers and three synthons could be radiolabeled in substantially higher RCYs (up to 2.5-fold) compared to those of previously published procedures, even from lower precursor amounts. Encouraged by these results, we applied our low-basicity method to the radiolabeling of highly base-sensitive tetrazines, which cannot be labeled using state-of-art direct aliphatic 18F-labeling procedures. Labeling succeeded in RCYs of up to 20%. We believe that our findings facilitate PET tracer development by opening the path toward simple and direct SN2 18F fluorination of base-sensitive substrates.

Synthesis of 3-Silylated 3-Sulfolenes from Propargylsilanes and their Reductive Desulfitation

Protonation of propargylsilanes induces 1,2-silyl group shift and provides 2-silylated dienes. If this reaction is performed in liquid SO2, the diene formation is followed by instant cheletropic SO2 addition, and 3-silylated 3-sulfolenes are obtained. Liquid SO2 as polar and Lewis acidic reaction medium makes it possible to use relatively weak Bronsted acid catalysts such as H2O and benzoic acid. Depending on the starting material, reductive desulfitation of 3-silylated 3-sulfolenes provides vinyl, allyl, or aliphatic silanes.

Efficient Suppression of Chain Transfer and Branching via Cs -Type Shielding in a Neutral Nickel(II) Catalyst.

An effective shielding of both apical positions of a neutral NiII active site is achieved by dibenzosuberyl groups, both attached via the same donors’ N‐aryl group in a C s‐type arrangement. The key aniline building block is accessible in a single step from commercially available dibenzosuberol. This shielding approach suppresses chain transfer and branch formation to such an extent that ultrahigh molecular weight polyethylenes (5×106 g mol−1) are accessible, with a strictly linear microstructure (<0.1 branches/1000C). Key features of this highly active (4.3×105 turnovers h−1) catalyst are an exceptionally facile preparation, thermal robustness (up to 90 °C polymerization temperature), ability for living polymerization and compatibility with THF as a polar reaction medium.

Efficient Suppression of Chain Transfer and Branching via Cs‐Type Shielding in a Neutral Nickel(II) Catalyst

AbstractAn effective shielding of both apical positions of a neutral NiII active site is achieved by dibenzosuberyl groups, both attached via the same donors’ N‐aryl group in a Cs‐type arrangement. The key aniline building block is accessible in a single step from commercially available dibenzosuberol. This shielding approach suppresses chain transfer and branch formation to such an extent that ultrahigh molecular weight polyethylenes (5×106 g mol−1) are accessible, with a strictly linear microstructure (&lt;0.1 branches/1000C). Key features of this highly active (4.3×105 turnovers h−1) catalyst are an exceptionally facile preparation, thermal robustness (up to 90 °C polymerization temperature), ability for living polymerization and compatibility with THF as a polar reaction medium.

Ring opening of methylenecyclopropanes with halides in liquid sulfur dioxide

Methylenecyclopropanes (MCP) undergo ring opening reactions with group I and II metal halides and ammonium halides in liquid SO2 to afford homoallylic halides, which are versatile reagents in organic synthesis. The developed reaction conditions are compatible with acid-labile substrates such as N-Boc-protected compounds. Liquid SO2 is a polar reaction medium with Lewis acid properties that solubilizes inorganic salts. The unique properties of SO2 were demonstrated by control experiments: 1) upon performing the reactions with the aforementioned salts in conventional solvents, the MCP ring opening was not observed either in the presence of catalytic amounts of H3PO4 (similar pKa to that of H2SO3), or in the absence of H3PO4; 2) a solution of SO2 in THF exhibited similar properties to that of liquid SO2.

Water-soluble Cu(II)-complexes of Schiff base amino acid derivatives as biological reagents and sufficient catalysts for oxidation reactions

Two novel water-soluble Cu(II) complexes (Cu-PSA and Cu-PSL) are synthesized from easily accessible Schiff base amino acid ligands (HPSA and HPS), as sodium sulfonate salts, obtained from D,L-phenylalanine and D,L-leucine, respectively. Their chemical composition is confirmed using various spectroscopic analyses (NMR, UV–vis, IR and mass spectroscopies, CHN micro-analyses, conductivities, TGA, and magnetism). The effect of sodium sulfonate group (Na+ SO3− group) on the chemical behavior of both Cu-PSA and Cu-PSL complexes is studied catalytically and biologically. Catalytically, Cu-PSA and Cu-PSL exhibit high reactivity in the (ep)oxidation of 1,2-cyclooctene and benzyl alcohol in polar reaction media, (acetonitrile or water) at 80 °C, under homogeneous reaction condition. Biologically, the Cu-complexes and their ligands (HPSA and HPS) are tested for antimicrobial activity against some pathogens strains. Both Cu-complexes reveal higher performance than their corresponding ligands. Cu-PSA and Cu-PSL complexes are also examined for ctDNA-interaction, which studied using various techniques including spectroscopy, viscosity and gel-electrophoresis. Despite, their low lipophilicity due to the sodium sulfonate group (salting group), they show potentially high electrostatic interaction with ctDNA. The binding potential of these compounds is also investigated by molecular docking showing the role of the central metal ion (Cu2+) and the salting group in the ctDNA interaction. For anticancer reactivity, both ligands (HPSA, HPSL), and their complexes (Cu-PSA or Cu-PSL) are examined against hepatocellular carcinoma (HepG2) cell line, breast carcinoma (MCF7) cell line and colon carcinoma (HCT-116) cell line. The obtained results are encouraging and after optimization the Cu-complexes could be potentially anticancer drug candidates.

Mild and Efficient Synthesis of Diverse Organo-AuI -L Complexes in Green Solvents.

An exceptionally mild and efficient method was developed for the preparation of (hetero)aryl‐AuI‐L complexes using ethanol or water as the reaction medium at room temperature and Ar‐B(triol)K boronates as the transmetalation partner. The reaction does not need an exogeneous base or other additives, and quantitative yields can be achieved through a simple filtration as the only required purification method, which obviates considerable waste associated with alternative workup methods. A broad reaction scope was demonstrated with respect to both the L and (hetero)aryl ligands on product Au complexes. Despite the polar reaction medium, large polycyclic aromatic hydrocarbon units can be incorporated on the Au complexes in very good to excellent yields. The approach was demonstrated for the chemoselective manipulation of orthogonally protected aryl boronates to afford a new class of N‐heterocyclic carbene‐Au‐aryl complexes. A mechanistic rationale was proposed.

The effect of synthesis reaction medium polarity on the degree of substitution (DS) value of carboxymethyl Kappa carrageenan (CMKC) synthesis: case study of isopropanolethanol-ethyl acetate mixture uses as synthesis reaction medium

This research aimed to analyze the effect of synthesis reaction medium polarity on the DS value of CMKC, we were studied the use of isopropanol-ethanolethyl acetate mixture at some proportion variation, as synthesis reaction medium, relation between polarity of reaction medium and DS value of CMKC, then determine optimum proportion of isopropanol-ethanol- ethyl acetate, as reaction medium, that was produced CMKC that has highest DS value. This research was done in two step (1) synthesize of cmkc by monochloroacetic acid (MCA) as etherification agent and mixture of isopropanolethanol-ethyl acetate as reaction medium (2) characterization of CMKC properties to determine the effect of synthesis reaction medium polarity against DS value. The results showed that reaction medium polarity affect on the value of DS. CMKC synthesis that was done in isopropanol-ethanol-etyl acetate 25:2:3 v/v has the highest DS value, 1.60.

Continuous flow synthesis of Micron size silica nanoparticles: parametric study and effect of dosing strategy

This work for the first time reports continuous flow synthesis of silica nano-particles of size over 1 μm using a simple tubular reactor. The systematic approach involves the study of effect of various parameters like: ammonia concentration, water concentration, electrolyte concentraton, temperature, solvent, residence time and mode of TEOS injection over a wide range. A combination of ethanol and butanol was used as the medium with relatively lower polarity. Various process parameters were optimized to obtain highly monodispersed particles of size up to 600 nm and high yield (up to 90%). Attempts of reducing the reaction time by increasing temperature or concentrations of any of the reagents resulted in significant polydispersity and even in the formation of random shape agglomerates. At the optimized conditions almost complete conversion of TEOS happenned within 40 min and further growth of particles was achieved by adding TEOS using multipoint injection approach. While multipoint dosing resulted in the formation of very small number of secondary particles, the larger particles continued to grow beyond 800 nm. Further reduction in the polarity of reaction medium was achieved by adding 20% v/v of toluene, which without changing homogeneity of the solution resulted in particles as large as 0.9–1.1 μm.

Influence of Levulinic Acid Hydrogenation on Aluminum Coordination in Zeolite-Supported Ruthenium Catalysts: A 27 Al 3QMAS Nuclear Magnetic Resonance Study.

The influence of a highly oxygenated, polar protic reaction medium, that is, levulinic acid in 2‐ethylhexanoic acid, on the dealumination of two zeolite‐supported ruthenium catalysts, namely Ru/H‐β and Ru/H‐ZSM‐5, has been investigated by 27Al triple‐quantum magic‐angle spinning nuclear magnetic resonance spectroscopy (3QMAS NMR). Upon use of these catalysts in the hydrogenation of levulinic acid, the heterogeneity in aluminum speciation is found to increase for both Ru/H‐ZSM‐5 and Ru/H‐β. For Ru/H‐ZSM‐5, the symmetric, tetrahedral framework aluminum species (FAL) were found to be mainly converted into distorted tetrahedral FAL species, with limited loss of aluminum to the solution by leaching. A severe loss of both FAL and extra‐framework aluminum (EFAL) species into the liquid phase was observed for Ru/H‐β instead. The large decrease in tetrahedral FAL species, in particular, results in a significant decrease in strong acid sites, as corroborated by Fourier transform infrared spectroscopy (FT‐IR). This decrease in acidity, evidence of the inferior stability of the strongly acidic sites in Ru/H‐β relative to Ru/H‐ZSM‐5 under the applied conditions, is considered as the main reason for differences seen in catalyst performance.

Synthesis of oxygenated fuel additives via glycerol esterification with acetic acid over bio-derived carbon catalyst

Glycerol derived from biodiesel (BD) production is oversupplied and requires urgent utilization. Hence, crude bio-derived glycerol was utilized as a carbon precursor for heterogeneous solid acid catalyst synthesis via partial sulphonation and carbonization in a single step. The as-synthesized catalyst was utilized to catalyze glycerol acetylation reaction with acetic acid to produce oxygenated fuel additives (diacetin and triacetin) and monoacetin. Under reaction conditions of 110°C, glycerol-to-acetic acid molar ratio of 3, 2wt% catalyst dose, and 3h reaction time, 88% combined DAG and TAG selectivity was attained with a corresponding glycerol conversion of 99%. The high surface acid sites density of the catalyst primarily contributed to its enhanced catalytic performance. The catalyst displayed sufficient heterogeneity and robustness in polar reaction media despite high hydrophilic acid sites density. Hence, it was reused in seven cycles of the experiment without experiencing significant deactivation.

Controllable synthesis of anisotropic silica/polymer composite particles via seeded dispersion polymerization

In this work, seeded dispersion polymerization was adopted to prepare anisotropic silica/polymer composite particles with controllable sizes and morphologies using the surface-modified silica particles as the seeds. Through this approach, submicron-sized silica/polymer particles with snowman-like, dumbbell-like, raspberry-like and core-shell structures could be easily fabricated in large scale. Many factors that might affect the morphologies of composite particles including the weight ratio of monomer/silica seeds, the polarity of reaction medium, reaction temperature, reaction time, the amount of crosslinking agent or the polarity of monomers were investigated. The results indicate that the interfacial tension between PS phases and SiO2 particles and the coalescence between growing polymer nodules over silica particles are responsible for the formation of different particle morphologies. It is interesting that snowman-like SiO2/PS particles could be afforded by two different processes: one was normally transformed from raspberry-like particles via the coalescence between growing polymer nodules; the other was formed directly at a high content of monomer. These different morphological particles may have important applications in biological/medical materials, optical materials, sensors, catalyst support, colloidal stabilizer, etc.

ChemInform Abstract: Palladium‐catalyzed Modification of Unprotected Nucleosides, Nucleotides, and Oligonucleotides

AbstractReview: 124 refs.

Palladium-catalyzed modification of unprotected nucleosides, nucleotides, and oligonucleotides.

Synthetic modification of nucleoside structures provides access to molecules of interest as pharmaceuticals, biochemical probes, and models to study diseases. Covalent modification of the purine and pyrimidine bases is an important strategy for the synthesis of these adducts. Palladium-catalyzed cross-coupling is a powerful method to attach groups to the base heterocycles through the formation of new carbon-carbon and carbon-heteroatom bonds. In this review, approaches to palladium-catalyzed modification of unprotected nucleosides, nucleotides, and oligonucleotides are reviewed. Polar reaction media, such as water or polar aprotic solvents, allow reactions to be performed directly on the hydrophilic nucleosides and nucleotides without the need to use protecting groups. Homogeneous aqueous-phase coupling reactions catalyzed by palladium complexes of water-soluble ligands provide a general approach to the synthesis of modified nucleosides, nucleotides, and oligonucleotides.

Alkylation of potassium ethyl acetoacetate: HSAB versus Marcus theory

Investigation of the reactions of potassium ethyl acetoacetate (KEAE) with C2H5X (X=Cl, Br, and I) in the gas-phase, tetrahydrofuran, and hexamethylphosphoramide was conducted at the B3LYP/6-311+G(d,p) level of theory. The C3- and O2-ethylations were examined to find out whether the Marcus or HSAB theory can explain the ambident reactivity of this nucleophile. It was found that the O2-ethylation of KEAE with all three halides is both kinetically and thermodynamically unfavourable in all media. Higher activation energy (as well as intrinsic activation barrier) in the O2 position is a consequence of the attractive forces between the oxygens and potassium, which are often unjustifiably neglected. This finding demonstrates that the Marcus theory is not applicable to the investigated reaction. On the other hand, the reaction is highly dependable on charge distribution and HOMO–LUMO gap in the reactant complexes, thus confirming the applicability of the HSAB rationale. The following conclusion was made: the smaller atomic number of the halogen in ethyl halide and more polar reaction medium, the more favourable charge distribution for the O2-ethylation of KEAE; the larger atomic number of the halogen and less polar reaction medium, the smaller HOMO–LUMO gap and more favourable the C3-ethylation.

AB-type monomers for the preparation of perfluorocycloalkene (PFCA) aryl ether polymers

A method for the preparation of AB-type monomers with complimentary fluoro-olefin and phenol functionalities is described. The three-step process is amenable to commercial scale up and uses widely-available, commercial reagents including bisphenols and perfluorocycloalkene (PFCA) compounds. Title compounds and intermediates were characterized via multi-nuclear NMR and FT-IR spectroscopy providing structural and mechanistic elucidation of PFCA step-growth polymerizations. The formation of vinyl and allyl substituted products were quantified and shown to be dependent on PFCA ring size and reaction medium. Nearly equal amounts of vinyl- and allyl-substituted products were observed with perfluorocyclohexene (PFCH) while 2–11% allyl-substitution was observed with perfluorocyclopentene (PFCP), depending on reaction medium polarity. Previous PFCA research and characterization of title compounds suggests that fluoride-catalyzed rearrangement is primarily responsible the formation of two substitution products. Polymerization of an AB-type monomer derived from bisphenol A is demonstrated and was shown to reproducibly result in film-forming polymers with higher molecular weights than previously described methods.

Iridafurans from the reaction of [Cp*IrCl2]2 with carbonyl conjugated terminal alkynes: Dependence of product on polarity of reaction medium

Reaction of the dimeric species [Cp*IrCl2]2 with terminal alkynes containing a conjugated carbonyl group results in C–C bond formation between two or three alkyne molecules, depending on the polarity of the reaction medium. The reaction pathway has been studied experimentally and computationally.

The shape-controlled synthesis and novel lithium storage mechanism of as-prepared CuC2O4·xH2O nanostructures

In a hydrothermal and solvothermal system at 120 °C, cylinder-like and rod-like nanostructures of hydrate copper oxalate (CuC2O4·xH2O) can be thoroughly synthesized in the absence of any shape-controlling additives, respectively. The self-assembly of primary nanocrystals has been investigated considering the polarity of reaction medium, and in the chemical formula of CuC2O4·xH2O the average x value of crystal water is estimated to discuss the superior lithium storage capability of hydrate products. The results show that cylinder-like aggregate of CuC2O4·xH2O (x ∼ 0.14) possesses an initial discharge capacity of 920.3 mAh g−1 with a residual capacity of 970.0 mAh g−1 at 200 mA g−1 over 100 discharge–charge cycles, while rod-like aggregate with a x value of ∼0.53 per chemical formula exhibits a higher initial capacity of 1211.3 mAh g−1 and a lower retention of 849.3 mAh g−1 under the same conditions. Furthermore, time-dependent measurements present a novel crystal-to-amorphous transformation of active substances, suggesting a positive effect of unavoidable crystal water on the superior lithium storage capability of nanostructured CuC2O4·xH2O.