SYNTHESIS OF CONDENSATION POLYMERS OF SALICYLIC ACID, FORMALDEHYDE AND ALKYL PRIMARY AMINES AND ITS APPLICATION AS A CATALYST FOR THE HYDROLYSIS OF p-NITROPHENYL ACETATE (PNPA) IN AQUEOUS SOLUTION

As a model of serine hydrolase, the condensation polymers of salicylic acid, formaldehyde and methyl amine, n-propyl amine, n-hexyl amine or n-lauryl amine were prepared by polycondensation catalyzed by sulfuric acid. It was confirmed by potentiometric titration and infrared spectrum that the polymers containing tertiary amino group possess the structure which resembles the internal salt of amino acid in weak basic and weak acidic solution:     

Spectroscopic structural studies of salicylic acid,salicylamide and aspirin

The electronic absorption spectra of the salicylic acid and the salicylamide molecules have been studied using SCF—CL calculations. The singlet and the triplet electronic transition energies have been calculated. The state functions of eight excited states for these molecules have been calculated in addition to the oscillator strengths, charge densities, ionization potentials and electron affinities. Our calculations lead to the presence of salicylic acid and salicylamide in the β-forms in which the carboxylic hydroxyl group or the amino group is directed toward the enolic hydroxyl group. The salicylic acid and the salicylamide molecules have the C_s point group symmetry, but the aspirin molecule has the C₁ point group symmetry, in which the acetyl group does not lie in the plane of the salicylic acid molecule.     

The elimination of small neutral molecules and fragments in mass spectra—I. Substituted salicylic acids and their derivatives

The mass spectra of various ring-substituted salicylic acids and derivatives thereof have been examined. Fragmentation pathways for derivatives of salicylic acid; 3-NO₂ salicylic acid; 5-I salicylic acid; 3-NO₂, 5-I salicylic acid; and 3-NH₂, 5-I salicylic acid are suggested. The major dissociations of these compounds are by elimination of the elements of neutral molecules, e.g. water, methanol, ketene (from the acetylated compounds) carbon monoxide, nitric oxide and nitrogen dioxide, leading to (iodo) phenoxy and (iodo) quinone type ion structures. These ions further decompose to yield the corresponding substituted cyclopentadienyl and cyclopropylium ions.     

Synthesis of visible light-driven Eu, N co-doped TiO2 and the mechanism of the degradation of salicylic acid

Europium and nitrogen co-doped TiO₂ was successfully synthesized by the precipitation–peptization method. The structure and properties of the catalysts were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectra. The photocatalytic efficiency was evaluated by monitoring the photocatalytic degradation of salicylic acid under visible light irradiation. It was verified that TiO₂ co-doped with nitrogen and 1% europium showed the highest photocatalytic activity. The adsorption isotherms were obtained by measuring the salicylic acid concentration before and after the dark adsorption at different original solution concentrations. The results illustrated that the doping of Eu was beneficial to the adsorption of salicylic acid. The probable degradation mechanism of salicylic acid was examined by the addition of NaF, Na₂S₂O₃, and K₂S₂O₈ as the probe molecules. It was verified that salicylic acid was first adsorbed on the surface of the catalysts, followed by the degradation by the photogenerated holes (h _vb ⁺ ).     

Antiproliferative effects of zerumbone-pendant derivatives on human T-cell lymphoid cell line Jurkat cells

Zerumbone is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. It is not only highly reactive but also has diverse bioactivities. Those effects derive from two conjugated double bonds of zerumbone and a carbonyl group in between, and we had already established a synthetic scheme for zerumbone-pendant derivatives without disturbing the conjugation system. Herein, twelve conjugates with salicylic acid or various benzoic acid derivatives were synthesized for evaluations of their antiproliferative effects on Jurkat cells as salicylic acid is bioactive and has a carboxylic group for coupling. Most of them resulted in IC₅₀ values as low as 1–10?μM, validating the utility of this activity-conserving strategy.     

Facile preparation of highly stable and active hybrid palladium nanoparticles: effectual,reusable and heterogeneous catalyst for coupling reactions

Palladium nanoparticles were supported on a bed of Fe₃O₄@‐NH₂@Murexide using a simple and efficient method, and characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies and inductively coupled plasma optical emission spectrometry. The catalytic system showed great efficiency in cross‐coupling reaction of aryl iodides and arylboronic acid and in Sonogashira cross‐coupling reaction in the green solvent EtOH–H₂O (1:1). The isolation and recovery of the catalyst were simple and facile and it could be used for several successive Suzuki–Miyaura coupling and Sonogashira cross‐coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

含水杨酸的缩聚物对P-硝基苯酚乙酸酯水解反应的催化作用(Ⅱ)

水杨酸、甲醛和烷基伯胺(烷基:甲基,正-丙基,正-己基或正-十二烷基)通过Mannich缩合反应制得了主链上既含有水杨酸基又含有叔胺基的线型缩聚物。用这些缩聚物催化P-硝基苯酚乙酸酯(PNPA)水解反应的动力学研究结果表明,缩聚物的催化活性随N-烷基侧链的链长增加而增加。在催化剂过量的条件下,带有十二碳烷基侧链的缩聚物催化PNPA水解反应时符合简单的Michaelis-Menten动力学历程。     

Catalytic Formation of Acrylate from Carbon Dioxide and Ethene

With regard to sustainability, carbon dioxide (CO₂) is an attractive C1 building block. However, due to thermodynamic restrictions, reactions incorporating CO₂ are relatively limited so far. One of the so‐called “dream reactions” in this field is the catalytic oxidative coupling of CO₂ and ethene and subsequent β‐H elimination to form acrylic acid. This reaction has been studied intensely for decades. However up to this date no suitable catalytic process has been established. Here we show that the catalytic conversion of ethene and CO₂ to acrylate is possible in the presence of a homogeneous nickel catalyst in combination with a “hard” Lewis acid. For the first time, catalytic conversion of CO₂ and ethene to acrylate with turnover numbers (TON) of up to 21 was demonstrated.     

Synthesis and characterization of sulfamic acid supported on Fe3O4 nanoparticles: A green,versatile and magnetically separable acidic catalyst for oxidation reactions and Knoevenagel condensation

Sulfamic acid immobilized on diethylenetriamine functionalized Fe₃O₄ nanoparticles (SA‐DETA‐Fe₃O₄) was successfully prepared and characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), X‐Ray diffraction (XRD) and scanning electron microscopy (SEM). The sulfamic acid was found as a magnetically separable and highly active catalyst for the oxidative coupling thiols, oxidation of sulfides. Furthermore, the SA‐DETA‐Fe₃O₄ showed the high catalytic activity in Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile and ethyl cynoacetate). The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for many cycles without deterioration in catalytic activity.     

Highly efficient recyclable heterogeneous palladium catalyst for C-C coupling, amination and cyanation reactions

An inexpensive, air-moisture stable and reusable PS-Pd(II)-anthra complex was synthesized by reacting chloro-methylated polystyrene with anthranilic acid to get polymer anchored ligand which was then reacted with PdCl₂ to get polymer anchored complex. This complex was characterized by different spectroscopic and elemental analyses. The activity of the Pd-complex as catalyst was tested for the Suzuki, Heck, Sonogashira cross-coupling and also for amination and cyanation reactions under various conditions. The catalyst exhibits high catalytic activities for the coupling of various aryl halides with organoboronic acid, alkene, alkyne and amine along with the cyanation of aryl halides providing excellent yields of desired product. Further, the catalyst can be easily recovered quantitatively by simple filtration and reused up to five times without sufficient loss of its catalytic activity.     

Ab initio study of the structure and tautomerism of internally hydrogen-bonded aromatic carbonyls: Salicylamide,salicylic Acid,and O-hydroxybenzoyl cyanide

We carried out an ab initio study at the 3–21 G level with full geometric optimization of three compounds with intramolecular hydrogen bonds in their most stable conformations, namely salicylamide, salicylic acid, ando-hydroxybenzoyl cyanide. The energy of the hydrogen bonds was estimated and their structural effects were analyzed. We also studied the stability of the tautomers resulting from a proton transfer between the oxygen atoms by analyzing the potential surfaces of the tautomerization process. The potential surfaces of salicylamide and salicylic acid showed a single minimum, while that of the cyanide showed a double minimum with a scarcely significant inverse barrier (3.01 kJ/mol). Single point calculations at the 6–31+G^* level on salicylic acid showed a trend to appear a second minimum in the potential surface. Both the strength of the hydrogen bond and the occurrence of stable tautomers were found to be clearly correlated with the electron-releasing and electron-withdrawing ability of the organic functions present in each compound (-NH₂,-OH and -CN, respectively).     

Preparation,characterization and application of silica‐supported palladium complex as a new and heterogeneous catalyst for Suzuki and Sonogashira reactions

An efficient heterogeneous Pd catalytic system has been developed, based on immobilization of Pd nanoparticles (PNPs) on a silica‐bonded propylamine–cyanuric–cysteine (SiO₂–pA–Cyan–Cys) substrate. The synthesized catalyst was characterized by transmission electron microscopy, scanning electron microscopy, FT‐IR, N₂ adsorption analysis (BET), TGA and inductively coupled plasma/atomic emission spectroscopy, and catalytic activity of this catalyst was investigated in the Suzuki and Sonogashira cross‐coupling reactions. The catalysts showed excellent performance in these two reactions, including various aryl halide derivatives (except aryl chloride derivatives) with phenylboronic acid and phenylacetylene under green conditions. Moreover, the catalyst was recycled for several runs without any significant loss of catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Direct Oxidative Coupling of Arenes with Olefins by Rh‐Catalyzed C?H Activation in Air: Observation of a Strong Cooperation of the Acid

A [{RhCl(cod)}₂]/CCl₃COOH system was developed for the oxidative coupling of non‐chelate‐assisted arenes with olefins in the presence of catalytic amounts of Cu(OAc)₂ ? H₂O as a co‐oxidant and oxygen as the terminal oxidant. The acid was an indispensable component in this system and played a very important role in the coupling reaction. This catalytic system was applied to the direct oxidative coupling of a series of arenes and olefins and the corresponding products were afforded in high yields with special chemo‐ and regioselectivity. This reaction provides an atom‐efficient route to vinylarenes, which are widely used in various fine chemicals.     

Pd-Catalyzed Difluoromethylations of Aryl Boronic Acids,Halides, and Pseudohalides with ICF2H Generated ex Situ

An expedient ex-situ generation of difluoroiodomethane (DFIM) and its immediate use in a Pd-catalyzed difluoromethylation of aryl boronic acids and ester derivatives in a two-chamber reactor is reported. Heating a solution of bromodifluoroacetic acid with sodium iodide in sulfolane proved to be effective for the generation of near stoichiometric amounts of DFIM for the ensuing catalytic coupling step. A two-step difluoromethylation of aryl (pseudo)halides with tetrahydroxydiboron as a low-cost reducing agent, both promoted by Pd catalysis, proved effective to install this fluorine-containing C₁ group onto several pharmaceutically relevant molecules. Finally, the method proved adaptable to deuterium incorporation by simply adding D₂O to the DFIM-generating chamber.     

Study on the Photodegradation of Salicylic Acid in Different Vehicles in the Absence and in the Presence of TiO2

In this work, the direct photolysis of salicylic acid, generally used as keratolytic agent in many dermatological products and as preservative in cosmetics, was investigated. The photodegradation of the acid under UVB irradiation was evaluated in different vehicles, such as water solutions at different pH, propylene glycol/water, and ethanol/water mixtures, sodium dodecyl sulphate solutions, and O/W emulsions prepared with Montanov 68 and Amphysol K as emulsifiers. The increase of pH enhanced the photodegradation of salicylic acid while the different vehicles protected the acid from the action of UVB radiations. However, the best protection was observed dissolving the acid in the lipid core of O/W emulsions, which probably removes the active from the polar environment that can promote the photolysis. The photocatalytic activity of TiO₂ on the degradation of salicylic acid also was evaluated. TiO₂ frequently is used as sunscreen in many cosmetic preparations. Salicylic acid and the pigment can be contained in the same solar formulation; hence, it can be interesting to study their interaction under UVB. TiO₂ enhanced the photodegradation of salicylic acid in all the media previously reported and its photocatalytic activity was influenced by the pH and by the components of the vehicles.     

Hybrid catalytic effects of K<Subscript>2</Subscript>CO<Subscript>3</Subscript> on the synthesis of salicylic acid from carboxylation of phenol with CO<Subscript>2</Subscript>

As a base-promoted Kolbe–Schmitt carboxylation reaction, the mechanism of synthesis of salicylic acid derivatives from phenols with CO₂ in the industry is still unclear, even up to now. In this paper, synthesis of 3,6-dichloro salicylic acid (3,6-DCSA) from 2,5-dichloro phenoxide and CO₂ was investigated in the presence of K₂CO₃. We show the reaction can proceed by itself, but it goes at a slower rate as well as a lower yield, compared to the case with the addition of K₂CO₃. However, the yield of 3,6-DCSA is only minorly affected by the size of K₂CO₃, which cannot be explained from the view of catalytic effect. Therefore, K₂CO₃ may on one hand act as a catalyst for the activation of CO₂ so that the reaction can be accelerated, while on the other hand, it also acts as a co-reactant in deprotonating the phenol formed by the side reaction to phenoxide, which is further converted to salicylate.     

Heteronuclear {Fe-Ba,Fe-Sr} salicylate complexes. Synthesis,structure, and physicochemical properties

The reactions of strontium and barium salicylates with iron nitrate gave heterometallic complexes {[FeSr₂(Sal)₂(SalH)₂(NO₃)(DMA)₄]} _n (I) and {[FeBa₂(Sal)₂(SalH)₃(DMA)₄(H₂O)]} _n (II). The solid compounds are one-dimensional coordination polymers where bridging function is performed by salicylic acid residues and the NO ₃ ^? group (in I). The salicylic acid residues are coordinated in the chelating bridging mode, their denticity ranging from 2 to 5. The IR spectra, magnetic properties, and thermal behavior of the complexes were studied.     

Palladium on magnetic Irish moss: A new nano‐biocatalyst for suzuki type cross‐coupling reactions

A novel heterogeneous magnetic palladium nano‐biocatalyst was designed by utilizing Irish moss, a family of sulfated polysaccharides extracted from algae, as a natural biopolymer. This magnetic Irish moss decorated with palladium (Pd–Fe₃O₄@IM) to form a biomagnetic catalytic system was synthesized and well characterized by FT–IR analysis, X‐ray powder diffraction, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, atomic absorption spectroscopy and transmission electron microscopy. The catalyst was stable to air and moisture and displayed high catalytic activity in ligand‐free Suzuki–Miyaura cross‐coupling reactions conducted under green chemistry reaction conditions. The aromatic ketones are produced by the cross‐coupling reaction between acid chlorides and aryl boronic acid derivatives in high yields.     

Aggregation Behavior of Titanium Dioxide Nanoparticles in Aqueous Environments

We report on the stability of titanium dioxide nanoparticles suspended in various aqueous solutions with and without the presence of a model organic contaminant—salicylic acid. The stability of the suspended nanoparticles was revealed by measuring the isoelectric point by means of zetapotential scans and measuring the growth kinetics of the hydrodynamic particle size by means of dynamic light scattering (DLS) under different pH conditions. Aggregated nanoparticle sizes were also examined using atomic force microscopy. It was found that salicylic acid had a dramatic impact on the aggregation behavior of TiO₂ nanoparticles, suggesting that salicylic acid adsorbs to TiO₂ nanoparticles surfaces.     

Reconsideration to the deactivation of TiO2 catalyst during simultaneous photocatalytic reduction of Cr(VI) and oxidation of salicylic acid

Photocatalytic reduction/oxidation and deactivation of TiO₂ photocatalyst was investigated in the systems composed of Cr(VI) and salicylic acid. The selection of analysis method of Cr(IV) was very important to the monitoring of the photocatalytic process. It was found that as previously reported, serious deactivation of TiO₂ catalyst in the simultaneous photo-reduction of Cr(VI) and oxidation of salicylic acid was incorrectly observed if the Cr(VI) level was analyzed by directly monitoring the absorbance at characteristic 348 nm band of Cr(VI), because it seriously suffers from the interferences of the intermediates generated from the degradation of salicylic acid. By using an appropriate method to determine the Cr(VI) concentration, it was observed that all the added Cr(VI) could be reduced, not showing marked deactivation of the photocatalyst. A long time photocatalytic reduction of Cr(VI) under UV illumination induced the deposition of Cr(III) species on the surface of TiO₂ particles, which could cause a mild deactivation of the photocatalyst. However, the accompanied oxidation of salicylic acid was demonstrated to depress the deactivation effect of the deposited Cr(III) species on the photocatalytic activity of the TiO₂ photocatalyst.