Sulfonic Acid–Functionalized Silica (SiO2-Pr-SO3H) as a Solid and a Heterogeneous Catalyst in Green Organic Synthesis: Recent Advances

The application of sulfonic acid–functionalized silica (SBA-Pr-SO₃H) as a catalyst in organic synthesis has become an efficient and green strategy for the selective construction of organic motifs. Therefore, the great efforts have been made by scientists to replace the conventional acid catalysts by sulfonic acid–functionalized silica used as solid, heterogeneous catalyst in various organic transformations. The sustainable advantage of sulfonic acid–functionalized silica is that it can be recovered and reused several times without loss of its efficiency. In this tutorial review, we attempt to give an overview about the use of sulfonic acid–functionalized silica as a catalyst in the synthesis of various organic compounds having industrial as well as pharmaceutical applications.     

Investigation of Electrochemical Copolymerization of 1‐Naphthylamineaniline in the Presence of Various Organic Sulfonic Acids

The electrochemical and electro activity properties of poly(aniline‐co‐1‐naphthylamine) thin films have been investigated in the presence of various organic sulfonic acids. Homo and copolymer thin films are synthesized electrochemically, under cyclic voltammetric conditions in aqueous solution of organic sulfonic acids (1 M), viz p‐toluene‐sulfonic acid (P‐TSA), methane‐sulfonic acid (MSA), 5‐sulfosalicylic acid (5‐SSA), camphor‐sulfonic acid (CSA) and dodecylbenzene‐sulfonic acid (DBSA) (0.25 M) on glass carbon (GC) electrode at room temperature. The cyclic voltammograms (CVs) show that the current densities are strongly influenced by the size and acidity of the organic acids which are present in electrolyte. Electocopolymerization was carried out at different ratios of NPA to ANI (0.07, 0.05, 0.03, 0.02, 0.014). The formation of copolymer was proved by cyclic voltammogram study.     

Mass transport characteristics of alkyl amines in a water/n-decane system

Rhenium (Re) nanoparticles have been synthesized by pulsed-laser decomposition of ammonium perrhenate (NH(4)ReO(4)) or dirhenium decacarbonyl (Re(2)(CO)(10)) in the presence of 3-mercaptopropionic acid (MPA) as capping agent, in both aqueous and organic media. Preliminary studies showed that the MPA-capped Re nanoparticles are capable of catalyzing the isomerization of 10-undecen-1-ol to internal alkenols via long chain migration of the C=C double bond at ca. 200°C. A one-pot synthesis of graphite-coated Re nanoparticles has also been achieved by pulsed-laser decomposition of Re(2)(CO)(10), due to photo-induced catalytic graphitization of the phenyl groups of PPh(3) on the surface of rhenium nanoparticles.     

Unstirred preparation of soluble electroconductive polypyrrole nanoparticles

Soluble electro-conductive polypyrrole nanoparticles (PPY-NPs) doped with organic sulfonic acid can be easily prepared via a new method for unstirred polymerization. The yield, size, morphology, electrical conductivity and solubility of the PPY-NPs were optimized by changing the feeding oxidant method, the sulfonic acid, the oxidant, and steric stabilizers. The PPY-NPs were characterized by FTIR, wide angle X-ray diffraction and four-point probe techniques. The morphology of the nanoparticles was investigated using scanning electron microscopy (SEM) and transmission electron microscopy. The PPY-NPs doped with p-toluenesulfonic acid exhibit a small diameter, an electrical bulk conductivity of 52.7 S·cm^?1, and can be obtained in high yield. PPY-NPs doped with naphthalene-2-sulfonic acid have a minimum mean diameter of around 71 nm (as found by SEM). All doped PPY-NPs are well solube in dimethylformamide, dimethyl sulfoxide, formic acid and sulfuric acid.     

Direct Photocatalysis for Organic Synthesis by Using Plasmonic‐Metal Nanoparticles Irradiated with Visible Light

Recent advances in direct‐use plasmonic‐metal nanoparticles (NPs) as photocatalysts to drive organic synthesis reactions under visible‐light irradiation have attracted great interest. Plasmonic‐metal NPs are characterized by their strong interaction with visible light through excitation of the localized surface plasmon resonance (LSPR). Herein, we review recent developments in direct photocatalysis using plasmonic‐metal NPs and their applications. We focus on the role played by the LSPR of the metal NPs in catalyzing organic transformations and, more broadly, the role that light irradiation plays in catalyzing the reactions. Through this, the reaction mechanisms that these light‐excited energetic electrons promote will be highlighted. This review will be of particular interest to researchers who are designing and fabricating new plasmonic‐metal NP photocatalysts by identifying important reaction mechanisms that occur through light irradiation.     

Preparation of Functionalized Carbon-Coated Cobalt Nanoparticles with Sulfonated Arene Derivatives,a Study on Surface Functionalization and Stability

The functionalization of magnetic nanoparticles has been an important field in the last decade due to the versatile applications in catalysis and biomedicine. Generally, a high degree of functionalities on the surface of the nanoparticles is desired. In this study, covalent functionalization of various aromatic sulfonic acids on carbon-coated cobalt nanoparticles are investigated on surface functionalization yield and stability. The nanoparticles are prepared via covalent linkage of an in situ generated diazonium on the graphene-like surface. Adsorption and wash experiments were performed to confirm a covalent bonding of the naphthalene derivatives on the nanoparticle surface. With an increased number of sulfonic acid groups on the aromatic compound a significantly lower loading is observed on the corresponding functionalized nanoparticles. This can be counteracted by a change of nitrite species. With this method, nanoparticles with a high number of sulfonic acid groups can be produced.     

Synthesis, characterization and evaluation of sulfonic resins as catalysts

Ion-exchange resins have been often used as catalysts especially those based on styrene-divinylbenzene copolymers with sulfonic acid groups in the aromatic rings of polymer chains. That is due to the advantages of heterogenous catalysis over the homogeneous acid catalysis. Moreover, resin catalysts can often lead to high selectivity in organic reactions due to the matrix effects. Therefore, the study of copolymers synthesis conditions to determine the type of polymer structure produced as well as the characterization of sulfonic resins obtained thereof are of great interest. The current paper describes the synthesis, characterization and evaluation as catalysts of sulfonic resins derived from polymer supports synthesized by aqueous suspension polymerization of styrene and divinylbenzene. The reaction conditions were varied and polymer supports with different physical properties and morphological characteristics were obtained. The polymer supports were chemically modified by sulfonation. The resultant sulfonic resins had their catalyst activity evaluated in the esterification of acetic acid with n-butanol.     

A new kind of polyion complex nanoparticles and the covalent drug-loading pattern for doxorubicin and pH-controlled release

The one-pot synthesis method was developed for the preparation of complex nanoparticles with a narrow size distribution and stable morphology. The vinyl monomers of (2-dimethylamino)ethyl methacrylate (DEMA) and diacetone acrylamide (DAA) were copolymerized in the presence of alginic acid in an aqueous solution without any organic solvents or surfactants, yielding stable complex nanoparticles in one-pot synthesis. The nanoparticle was composed of the complex of poly(DEMA-co-DAA) and alginic acid. The complex was formed via electrostatic interaction between polycations of DEMA and polyanions of alginate. The residual alginate segment around the core formed the shell of the nanoparticles. The average diameter of the nanoparticles varied from 120 to 213 nm when the molar percentage of DAA changed from 0.5 to 0 with respect to DEMA. The anti-cancer drug doxorubicin could be loaded onto the nanoparticles with a high-loading efficiency through the formation of polymer–drug conjugate. The drug release could be controlled by adjusting the pH value of the medium.     

Heteronuclear coordination compounds of copper and cobalt in urethane-yielding reactions

Heteronuclear coordination compounds capable of catalyzing the low-temperature dissociation of urethane groups were synthesized on the basis of copper and cobalt chlorides. The study was performed with an urethane prepolymer produced from oligoester diol and 2,4-toluylene diisocyanate. It was found that the dissociation of urethane groups in the prepolymer is accompanied by formation of carbodiimides and release of 2,4-toluylene diisocyanate. As a result of the subsequent redox interaction, Cu(II) ions are mostly converted to Cu(I), and the involvement of isocyanate groups in the para-position into the reaction processes leads to formation of azoaromatic derivatives. It is shown that their coordination binding by Co(II) ions strongly affects both the supramolecular organization of polyurethanes and a set of their physicomechanical properties.     

Synthesis of size-controlled and shaped copper nanoparticles

The synthesis of stable, monodisperse, shaped copper nanoparticles has been difficult, partially because of copper's propensity for oxidation. This article reports the findings of an investigation of a synthetic route for the synthesis of size-controllable and potentially shape-controllable molecularly capped copper nanoparticles. The approach involved the manipulation of reaction temperature for the synthesis of copper nanoparticles in organic solvents in the presence of amine and acid capping agents. By manipulating the reaction temperature, this route has been demonstrated for the production of copper nanoparticles ranging from 5 to 25 nm. The size dependence of the melting temperature of copper nanoparticles, especially for surface melting, is believed to play an important role in interparticle coalescence, leading to size growth as the reaction temperature is increased. Control of the reaction temperature and capping molecules has also been demonstrated to produce copper nanoparticles with different shapes such as rods and cubes. The previously proposed combination of the selective formation of a seed precursor and a selective growth direction due to the preferential adsorption of capping agents on certain nanocrystal facets is believed to be responsible for shape formation by kinetically controlling the growth rates of crystal facets. The nanoparticles are characterized using TEM, XRD, and UV-visible techniques. A mechanistic consideration of the size control and shape formation is also discussed.     

Catalysis for green chemistry: ultrahigh loaded mesoporous solid acids

The development and applications in organic synthesis of new mesoporous solid catalysts is proving to be one of the most interesting and important subjects in green and sustainable chemistry. With high levels of organic functionality on the surface, these materials which can be considered as inorganic–organic hybrids, are compatible even with very low polarity organic media and can be used in various types of organic reactions. Some of the most interesting are solid acids such as solid sulfonic acid and solid peracids which are safe and environmentally less-damaging alternatives to conventional reagents.     

Mesoporous silica materials with an extremely high content of organic sulfonic groups and their comparable activities with that of concentrated sulfuric acid in catalytic esterification

Mesoporous silica materials (HS-JLU-20) with an extremely high content of mercaptopropyl groups have been successfully synthesized using fluorocarbon-hydrocarbon surfactant mixtures through a simple co-condensation approach of tetraethyl orthosilicate (TEOS) and (3-mercaptopropyl)trimethoxysilane (MPTS), which are characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption isotherms, transmission electron microscopy (TEM), CHNS elemental analysis, thermogravimetry analysis (TGA), and (29)Si NMR spectroscopy. The results show that HS-JLU-20 samples with molar ratios of MPTS/(MPTS + TEOS) at 0.5-0.8 in the starting synthetic gels still show their mesostructures, while HS-SBA-15 with the molar ratio of MPTS/(MPTS + TEOS) at 0.50 completely loses its mesostructure in the absence of fluorocarbon surfactant. Possibly, fluorocarbon surfactant containing N(+) species with a positive charge could effectively interact with negatively charged mercapto groups in the synthesis of HS-JLU-20 materials, resulting in the formation of mesoporous silicas with good cross-linking of silica condensation even at an extremely high content of organic mercapto groups. More interestingly, after the treatment with hydrogen peroxide, HSO(3)-JLU-20 materials with an extremely high content of organic sulfonic groups exhibit comparable activity with liquid concentrated sulfuric acid in catalytic esterification of cyclohexanol with acetic acid.     

Synthesis of Pyrimidinone and 5‐unsubstituted 4, 6‐diarylpyrimidine‐2(1H)‐ones by Using Nano Magnetic Catalyst under Solvent Free Condition

Nano magnetic‐supported sulfonic acid is found to be a powerful and reusable heterogeneous catalyst for the efficient synthesis of pyrimidinones. In this study we use various ketones such as acetophenone and cyclopentanone instead of β‐keto ester in one‐pot synthesis of pyrimidinone at biginelli like reaction. Our objective is to improve conditions for the synthesis of multicomponent reactions using nano magnetic catalyst under solvent free condition. A number of excellent and significant results have been developed that lead our perspective understanding the effect of the magnetic nanoparticles when they are used as catalysts.     

Water-medium and solvent-free organic reactions over a bifunctional catalyst with Au nanoparticles covalently bonded to HS/SO3H functionalized periodic mesoporous organosilica

An operationally simple approach for the preparation of a new class of bifunctional Au nanoparticle-acid catalysts has been developed. In situ reduction of Au(3+) with HS-functionalized periodic mesoporous organosilicas (PMOs) creates robust, fine Au nanoparticles and concomitantly produces a sulfonic acid moiety strongly bonded to PMOs. Characterizations of the nanostructures reveal that Au nanoparticles are formed with uniformed, narrow size distribution around 1-2 nm, which is very critical for essential catalytic activities. Moreover, the Au nanoparticles are mainly attached onto the pore surface rather than onto the outer surface with ordered mesoporous channels, allowing for maximal exposure to reaction substrates while minimizing Au nanoparticle leaching. Their higher S(BET), V(P), and D(P) than either the Au-HS-PMO(Et) or the Au/SO(3)H-PMO(Et) render the catalyst with comparably even higher catalytic efficiency than its homogeneous counterparts. Furthermore, the unique amphiphilic compartment of the Au-HS/SO(3)H-PMO(Et) nanostructures enables organic reactions to proceed efficiently in a pure aqueous solution without using any organic solvents or even without water. As demonstrated experimentally, remarkably, the unique bifunctional Au-HS/SO(3)H-PMO(Et) catalyst displays higher efficiencies in promoting water-medium alkyne hydration, intramolecular hydroamination, styrene oxidation, and three-component coupling reactions and even the solvent-free alkyne hydration process than its homogeneous catalysts. The robust catalyst can be easily recycled and used repetitively at least 10 times without loss of catalytic efficiency. These features render the catalyst particularly attractive in the practice of organic synthesis in an environmentally friendly manner.     

Novel silver/polyurethane nanocomposite by in situ reduction: Effects of the silver nanoparticles on phase and viscoelastic behavior

A novel silver/poly(carbonate urethane) nanocomposite was prepared through in situ reduction of a silver salt (AgNO₃) added to a solution consisting of a commercial poly(carbonate urethane) dissolved in N,N‐dimethylformamide (DMF). In this system, the presence of the poly(carbonate urethane) was proved to protect the silver nanoparticles, whose formation was confirmed by means of UV–vis spectroscopy, from aggregation phenomena. The silver morphology developed in the solid state after DMF casting was imaged by FESEM. Homogeneous dispersion of silver nanoprisms in the poly(carbonate urethane) matrix was clearly observed. The effects of dispersion of silver nanoparticles within the poly(carbonate urethane) matrix were investigated by means of ATR‐FTIR and multifrequency dynamic mechanical thermal analyses. The obtained results revealed that the presence of silver nanoparticles modifies both the phase and the viscoelastic behaviors of poly(carbonate urethane). As a matter of fact, the hydrogen bond formation in the hard and soft segments was found to be hindered and the molecular motions of the soft segments were restricted, because a comparatively higher activation energy was required for the related α‐relaxation process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 344–350, 2008     

Photo catalytic degradation of linear alkylbenzene sulfonic acid

Linear alkylbenzene sulfonic acid (LAS) is a common substance used in the production of detergents in the world. This is an organic material with its structure made of benzene ring and double bonds. This structure creates many problems for the environment and humans. Up to now, various methods have been used to eliminate this pollution. A recently proposed method to remove this organic pollution is advanced oxidation processes. Photocatalytic degradation is also an efficient method to destroy organic structures. In this research, TiO₂ nanoparticles are used as a photocatalyst that is activated by UV irradiation. TiO₂ nanoparticles and pollution suspension are incorporated into the new design of the reactor with coaxial cylinders in which the inner cylinder rotates at a constant speed. The results show that in low concentrations of LAS, using TiO₂ nanoparticles, the time to reach pollution elimination is reduced significantly. In higher concentrations of LAS, UV irradiation is more effective than activated TiO₂ nanoparticles.     

Au nanoparticles and polyaniline coated resin beads for simultaneous catalytic oxidation of glucose and colorimetric detection of the product

In this letter, we report the synthesis of Au nanoparticles (NPs) and polyaniline (PANI) on the same cation-exchange resin beads and demonstrate their use in catalyzing the oxidation of glucose to gluconic acid by Au NPs and simultaneously in detecting the formation of the acid by the color change of PANI. The synthesis was carried out by exchanging the cations of the resins with HAuCl4 and anilinuium chloride and then reducing the metal ions by NaBH4 to produce Au NPs followed by polymerization of aniline using H2O2. The green emeraldine salt form of PANI thus obtained was treated with NaOH to be converted to blue emeraldine base before use. The deposition of Au NPs was confirmed by a change in color of the bead, visible spectroscopy, X-ray diffraction, and scanning electron microscopic measurements. On the other hand, the presence of PANI was confirmed by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. The formation of gluconic acid from glucose was confirmed by FTIR spectroscopy. We could detect the presence of glucose of a minimum 1.0 mM concentration in water, using the present method. Our experimental observations demonstrate the possibility of the incorporation of multifunctional components on the surfaces of resins for carrying out a chemical reaction as well as detection of the product.     

Preparation of fluoroalkyl end-capped cooligomers/silica nanoparticles: A new approach to fluorinated nanoparticle inhibitors of Human Immunodeficiency Virus Type 1 and Simian Immunodeficiency Virus (SIVmac)

Fluoroalkyl end-capped acrylic acid and sulfonic acid cooligomers reacted with tetraethoxysilane (TEOS) and silica/nanoparticles under alkaline conditions to afford the corresponding cooligomers/silica nanoparticles (mean diameters: 32-173 nm) with a good dispersibility and stability in aqueous and organic media. Interestingly, fluorinated nanoparticles containing carboxy groups were found to exhibit a potent and selective anti-HIV-1 activity in vitro. In contrast, fluorinated cooligomers containing sulfo groups were shown to have a potent and selective anti-SIV_mac activity in vitro.     

Preparation and Characterization of Stearate-Capped Titanium Dioxide Nanoparticles

The preparation of titanium dioxide nanoparticles capped with stearate by sol-gel methods is presented in this paper. The nanoparticles are characterized by Fourier transform infrared spectroscopy and by X-ray photoelectron spectroscopy. Existence of the organic layer can be confirmed by the results of characterizations, which also indicate that the inorganic nuclei and organic surface layer are linked with chemical bonds. The nanoparticles are poorly crystallized based on the X-ray diffraction pattern. The mechanism of formation of the organo-capped nanoparticles is proposed to be competitive reactions between water and stearic acid, which is similar to a polymerization and inhibition processes. A structural model for organo-capped nanoparticles is also proposed. Copyright 2000 Academic Press.     

Porous Organic Salts Composed of Terphenyl Sulfonic Acid and Their Bottleneck Designability

Porous organic salts (POSs) are constructed through a strong charge-assisted hydrogen bond between sulfonic and amino groups. The molecular design of sulfonic acid, the linker part, enables various porous structures. In the current work, we synthesized p-terphenyl-4,4’’-disulfonic acid (TPDS), whose molecular structure can be easily modified by organic synthesis. Combining of TPDS and bulky tri-p-tolylmethanamine (TPMA-Me), which has three methyl groups at each para-position of the phenyl groups of triphenylmethylamine (TPMA), gave POS with one-dimensional pore channels having two different types of bottlenecks. The central benzene ring of TPDS is exposed on the surface of the pore. Therefore, we combined 4,4′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzenesulfonic acid (BTDBS) containing 2,1,3-benzothiadiazole (BT) with TPMA-Me, and successfully constructed a one-dimensional pore channel with a bottleneck of 3.5 Å, by exposing BT to the surface of the pore. BTDBS/TPMA-Me exhibited a large adsorption/desorption hysteresis of nitrogen because of the bottleneck, electronic state of BT, and larger oxygen adsorption than the isostructural TPDS/TPMA-Me. Systematic and intended modulation of the pore structure of POS based on the modification of sulfonic acid was demonstrated, and for the first time, we established a precise design methodology for a one-dimensional pore channel with a bottleneck and high crystallinity in metal-free porous organic materials.