Stabilization of Water‐Soluble Antioxidant in Water‐in‐Oil‐in‐Water Double Emulsions

Abstract

In this study, we are introducing a method that can effectively stabilize antioxidants in water‐in‐oil‐in‐water (W/O/W) double emulsions. Preliminarily, stable W/O/W double emulsions were produced by manipulating the characteristics of internal aqueous phase via two‐stage emulsification, resulting consequently in the formation of fine internal water droplets in the dispersed oil droplets. From conductivity measurements that can determine the elution amount of internal aqueous phase, it was confirmed that the double emulsion stability could be improved by treating the internal aqueous phase with a hydroxypropyl‐beta‐cyclodextrin. In this study, kojic acid, 5‐hydroxy‐2‐(hydroxymethyl)‐4‐pyrone was selected as a model antioxidant. The stabilization of kojic acid was attempted by locating it in the internal water droplets of the stable W/O/W double emulsions. The stability of kojic acid in the double emulsion system could be maintained at 90% for 10 weeks at high temperature. We believe that these stable W/O/W double emulsions could be used meaningfully as a carrier for many unstable antioxidants.     

Regioselectivity in Alkylation Reactions of 1,2‐O‐Stannylene Acetals of d‐Arabinofuranose

The synthesis of β‐arabinofuranosides via alkylation of 1,2‐O‐stannylene acetal intermediates has been studied. With reactive alkyl halides (benzyl bromide, allyl bromide, and p‐methoxybenzyl chloride), the method provides a mixture of β‐arabinofuranosides and 2‐O‐alkylated lactols in ratios of 4:1 to 1:1.5. However, with carbohydrate‐derived electrophiles, no alkylated products are produced. It appears, therefore, that the method is limited to the preparation of β‐arabinofuranosides of simple alcohols. Through the use of computational chemistry, we have explored the conformational properties of one of these stannylene acetals and propose that these species exist in more than one conformation in solution and that this contributes to the relatively poor regioselectivity in these reactions.     

Stereoselective Synthesis of cis‐1‐Aryl‐2‐benzoyl‐3,3‐dicyanocyclopropanes in Water

The highly stereoselective preparation of cis‐1‐aryl‐2‐benzoyl‐3,3‐dicyanocyclopropanes with arsonium salt and olefin in water is described. It is simple, efficient, and environmentally benign.     

Utility of 1‐Chloro‐3,4‐dihydronaphthalene‐2‐carboxaldehyde in the Synthesis of Novel Heterocycles with Pharmaceutical Interest

Ethyl α‐cyano‐β‐(1‐chloro‐3,4‐dihydronaphthalene‐2‐yl) acrylate (2) was prepared by the Knoevenagel condensation of 1 with ethyl cyanoacetate. Compound 2 was used as the key intermediate to prepare Schiff bases (3a, b), benzo[c]acridine (4), naphthyl thiopyrimidine (5), and pyrazolo[2,3‐a]‐benzo[h]quinazoline (6) derivatives through its reaction with hydrazines, p‐ansidine, thiourea, and 3,5‐diamino‐4‐phenylazopyrazole, respectively. Base‐catalyzed cyclocondensation of 1 with hippuric acid gives oxazolone derivative (7). Reaction of compound 7 with aniline gave imidazolone derivative (9). Treatment of compound 1 with different types of diaminopyrazoles gave 6,7‐dihydro‐pyrazolo[2,3‐a]‐benzo[h]quinazoline (10–13) derivatives. The multicomponent reaction of compound 1 with pyrazolone and malononitrile in the presence of ammonium acetate furnished pyrazolo[3,4‐b]‐benzo[h]quinoline (14) while in the presence of piperidine afforded benzo[h]chromeno[2,3‐c]pyrazole derivative 15.     

One‐Pot Synthesis of 2‐Acylimino‐3‐aryl‐thiazoline Derivatives in Aqueous Media

A one‐pot, two‐step synthesis for acyliminothiazolines by treated N,N′‐substituted thioureas with α‐bromocarbonyl compounds under aqueous media was described. Compared to the classical reaction in organic solvents, this method consistently has the advantage of short reaction times, convenient procedures, and mild reaction conditions.     

RAFT Polymerization of Styrene in the Presence of 2‐Nonyl‐benzoimidazole‐1‐carbodithioic Acid Benzyl Ester

A novel dithiocarbamate, 2‐nonyl‐benzoimidazole‐1‐carbodithioic acid benzyl ester ( 1a ), was synthesized and successfully used in RAFT polymerization of styrene in bulk with thermal initiation. The effect of molar ratio of styrene to RAFT agent on the polymerization was investigated. The linear relationship between ln([M]₀/[M]) and polymerization time indicated that the polymerization was first‐order with respect to monomer concentration. The molecular weights increased linearly with monomer conversion and were close to corresponding theoretical values. The molecular weight distributions (M _w /M _n ) kept very narrow (M _w /M _n <1.1) at a wide range of conversions of 14.2% to 73.3%. The obtained polymer had a strong ultraviolet absorption at 329 nm, which indicated that the 1a moiety remained at the end of polymer chain.     

Stability of dicyclohexyl‐18‐crown‐6‐hydrogen complex in nitrobenzene saturated with water

From extraction experiments with 22 Na as a tracer, the extraction constant corresponding to the equilibrium H⁺ (aq)+NaL ⁺(nb) HL⁺ (nb)+Na ⁺ (aq) in the twophase waternitrobenzene system (L = dicyclohexyl18crown6; aq = aqueous phase, nb = nitrobenzene phase) wasevaluated in the form log K ex (H⁺ , NaL⁺ ) = 0.2. Further, the stability constant of the complex HL⁺ in nitrobenzene saturated with water wascalculated for a temperature of 25 °C : log bnb (HL⁺ ) = 7.7.     

Effect of Emulsification Method on the Properties of Lecithin‐ and PGPR‐Stabilized Water‐in‐Oil‐Emulsions

Water‐in‐oil (w/o) emulsions were prepared with phosphatidylcholine‐depleted lecithin or polyglycerol polyricinoleate (PGPR) as emulsifying agents. The effect of different laboratory emulsification devices and the effect of sodium chloride on particle size distribution, coalescence stability, and water droplet sedimentation were investigated. The properties of lecithin‐stabilized w/o emulsions were found to depend more strongly on the emulsifying method than those prepared with PGPR. The rotor‐stator system was not suitable for preparing stable w/o emulsions with lecithin. Whereas the addition of salt was essential to achieve coalescence‐stable emulsions prepared with PGPR, the presence of NaCl favored the coalescence of water droplets and phase separation in emulsions containing lecithin.     

Synthesis of Methyl 2‐Methylazulene‐3‐carboxylate in the Presence of Molecular Sieves and Reaction with N‐Bromosuccinimide

The preparation of methyl 2‐methylazulene‐1‐carboxylate (1) was carried out in the presence of molecular sieves to obtain a good yield. The product was subjected to bromination under different reaction conditions to obtain methyl 1‐bromo‐2‐methylazulene‐1‐carboxylate (2) and methyl 1‐bromo‐2‐(bromomethyl) azulene‐1‐carboxylate (3).     

Studies of Kinetics of Coalescence of Water‐in‐Furrial Crude Oil Emulsions by Confocal Microscopy

The kinetic of coalescence of water in Furrial crude oil emulsions (W/O) during the initial stage of demulsification process is showed through of high‐resolution image micrographics by using a confocal microscope. Furrial crude oil from Monagas state is a crude oil extra heavy with severe flocculation/aggregation problems. The kinetic of the initial stage in the coalescence process is critical and of great importance in the definition of the foreword behavior. This information allowed us to characterize the demulsification rate process in a Furrial crude oil. Total W/O emulsion separation was achieved about of 2 hours at 80ºC. The initial fast coalescence is characterized by a short binary coalescence time, which is followed by a large binary coalescence time. Our results demonstrate that the initial coalescence rate determinate the time necessary to achieve a total separation.     

Effect of Substitution in Stannic Chloride–Mediated Heterocyclization of 4‐Allyl‐3‐hydroxyquinolin‐2(1H)‐ones

Effect of substituents at the allylic position in a stannic chloride–iodine–mediated heterocyclization of 4‐allyl‐3‐hydroxyquinolin‐2(1H)‐ones for the regioselective formation of five‐ and six‐membered heterocyclic rings has been rationalized by the application of restricted Hatree–Fock calculation.     

Application of Sulfinyl bis(2,4‐dihydroxythiobenzoyl) in the Synthesis of N‐Substituted 2‐Amino‐5‐(2,4‐dihydroxyphenyl)‐1,3,4‐thiadiazoles

One‐stage synthesis of N‐substituted 2‐amino‐5‐(2,4‐dihydroxyphenyl)‐1,3,4‐thiadiazoles is described. The compounds were prepared by the reaction of the sulfinyl bis(2,4‐dihydroxythiobenzoyl) (STB) with 4‐substituted 3‐thiosemicarbazides. STB was obtained from 2,4‐dihydroxybenzenecarbodithioic acid and thionyl dichloride. The structure of compounds was confirmed by IR, ¹H NMR, ¹³C NMR, and EI‐MS data.     

Sonochemical Synthesis of 1,4‐Disubstituted 1,2,3‐Triazoles in Aqueous Medium

An ultrasound‐accelerated fast and efficient three‐component reaction for the regioselective synthesis of l,4‐disubstituted 1,2,3‐triazoles using different alkyl and allyl halides, terminal alkynes, and sodium azide in water at room temperature has been developed using CuI as catalyst. Ultrasonication dramatically decreases the reaction times.     

Synthesis of Functionalized Pyrroles by Reaction of 3,4‐Diacetylhexane‐2,5‐dione with Primary Amines in Water

3,4‐Diacetylhexane‐2,5‐dione (tetra‐acetylethane) undergoes a complex reaction with primary amines in boiling water to produce N‐alkyl‐3‐acetyl‐2,5‐dimethylpyrroles, together with small quantities of N‐alkyl‐3,4‐diacetyl‐2,5‐dimethylpyrroles and 2,5‐dimethyl‐1H‐pyrrol‐3‐yl‐vinyl‐acetamides. When the reaction was carried out in methanol at room temperature, the yields of the latter products increased.     

Spectrophotometric Determination of Gold in Water and Ore with 2‐Carboxyl‐1‐Naphthalthiorhodanine

Abstract

This paper reports on the synthesis of a new chromogenic reagent, 2‐carboxyl‐1‐naphthalthiorhodanine (CNTR). A high sensitive, selective, and rapid method for the determination of gold based on the rapid reaction of gold with CNTR and the solid phase extraction of the colored chelate with a reversed phase polymer‐based C₁₈ cartridge was developed. In the presence of 0.05–0.5 mol L^?1 of phosphoric acid solution and emulsifier‐OP medium, CNTR reacts with gold to form a red chelate of a molar ratio 1∶3 (gold to CNTR). This chelate was enriched by the solid phase extraction with a polymer‐based C₁₈ cartridge and the retained chelate was eluted from the cartridge with dimethyl formamide (DMF). The enrichment factor of 100 was achieved. In the DMF medium, the molar absorptivity of the chelate is 1.35×10⁵ L · mol^?1 · cm^?1 at 540 nm. Beer's law is obeyed in the range of 0.01～2 µg mL^?1 in the measured solution. The relative standard deviation for 11 replicates sample of 0.5 µg L^?1 level is 2.05%. The detection limit, based on three times the standard deviation is 0.02 µg L^?1 in the original sample. This method was applied to the determination of gold in water and ore with good results.     

Synthesis of Per‐acetyl d‐fucopyranosyl Bromide and Its Use in Preparation of Diphyllin d‐fucopyranosyl Glycoside

The per‐O‐acetyl‐d‐fucosyl bromide (9) was expediently prepared for C‐6 deoxygenation of d‐galactose in six steps in 32.5% yield. Employing phase transfer catalysis glycosylation (PTC), d‐fucopyranosyl diphyllin (4), the analog of natural diphyllin glycoside, was synthesized by using 9 as the glycosyl donor in 67.1% in two steps. The product was identified by ¹H NMR, ¹³C NMR, and HRMS. Its abilities to inhibit the growth of cancer cells in vitro also are discussed.     

Palladium‐Catalyzed Enyne Cyclization of 2′‐Alkenyl 2‐Alkynoates in Imidazolium‐Type Ionic Liquids

The use of [bmim][BF₄], [bmim][PF₆], and [bmim][Cl] ILs as the solvents in Pd(II)‐catalyzed enyne cyclization of 2′‐alkenyl 2‐alkynoates in the presence of cupric chloride has been investigated. The Z/E stereoselectivity of the reaction could range from 90:10 to 4:96 by tuning the amount of LiCl in ILs. After the separation of the product, the IL–catalyst mixture could be recovered by treatment with hydrochloric acid and recycled several times without an obvious loss of catalytic activity.     

Spectrophotometric Determination of Nitrite in Water Samples with 4‐(1‐Methyl‐1‐Mesitylcyclobutane‐3‐yl)‐2‐Aminothiazole

Abstract

A simple, sensitive, and specific spectrophotometric method for the measurement of nitrite in water has been developed and optimum reaction conditions along with other analytical parameters have been evaluated. The azo dye, 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐(p‐N,N‐dimethylazobenzene)‐1,3‐thiazole was synthesized with the reaction of 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐aminothiazole and N,N‐dimethyl aniline in acidic medium. Obtained azo dye has been characterized by infrared (IR), ¹H nuclear magnetic resonance (NMR), and microanalysis methods. The dye shows an absorption maximum at 482 nm. The method is optimized for acid concentration, pH, amount of reagents required, time, and interfering species. All the determinations were carried out at this wavelength throughout the work. At an analytical wavelength of 482 nm, Beer's law is obeyed over the concentration range 0.05 to 2.00 µg nitrite per mL analyte. The molar absorptivity, Sandell's sensitivity, and relative standard deviation are 2.03×10⁴ L mol^?1 cm^?1±251.3 (95%), 2.28×10^?3 µg cm^?2, and 2.74% (n=10), respectively. The detection limit of the method is 0.012 µg ml^?1 of nitrite ion. The method was succesfully applied to the determination of nitrite in tap water and lake water.     

Effect of Triton‐X‐100 Solvent in the Micellar Catalysis of the Aquation of Tris(2‐nitroso‐1‐naphtholate) Ferrate (II)

The effect of triton‐X‐100 micelles on the aquation of Fe(C₁₀H₆N₂O)₃ ²⁺ has been investigated with triton‐X‐100 as solvent. In liquid triton‐X‐100, over a range of [H₂O] _T (0.0–3 M), significant rate enhancement factors of 50–150 are observe. Acid inhibits the rate of aquation at fixed [H₂O] _T . A mechanism based on effective solvent participation in a chemical environment similar to that in reversed micelles is proposed in liquid triton‐X‐100 with dispersed water pockets. This mechanism predicts direct H₂O substitution into the coordination sphere of Fe(C₁₀H₆N₂O)₃ ²⁺ in the highly polar water pockets or cavities where the Fe (II) complex molecules are solubilized. Changes in the tumbling rate, structure, and activity of water are suggested to account for the observed changes in the rate of aquation as a function OH [H₂O] _T . All k _ψ–[H₂O] _T profiles are structured and exhibit maxima with k _ψ(max) shifted to progressively higher [H₂O] _T as the fixed concentration [H⁺] _T is increased.     

Crystal and Molecular Structure of 2,3‐Pentamethylene‐3,4‐Dihydroquinazolone‐4 Nitrate. Conjugation Effects in the Series of Tricyclic Quinazolines

The structure of 2,3pentamethylene3,4dihydroquinazolone4 nitrate was determined by means of Xray diffraction. Analysis was performed of the geometry of the heterocyclic ring in 2,3tri, tetra, and pentamethylene3,4dihydroquinazolones4, quinazolines, and their salts with inorganic acids and complexes with metal ions. It is found that in the N(1)—C(2)—N(3) fragment in the bases of quinazolines and quinazolones4, the conjugation is less pronounced than that in the protonated (salt) forms.