- Photochemical behaviour of dichlorprop [(±)-2-(2,4-dichlorophenoxy)propanoic acid] in aqueous solution
-
Aqueous solutions of dichlorprop were irradiated under different conditions of pH, wavelength and oxygenation. The photochemical behaviour was found to be complex and many photoproducts were formed. However, at low concentrations the main photoproducts we
- Meunier, Laurence,Gauvin, Emmanuelle,Boule, Pierre
-
-
Read Online
- Iridium-Catalyzed C(sp3)?H Addition of Methyl Ethers across Intramolecular Carbon–Carbon Double Bonds Giving 2,3-Dihydrobenzofurans
-
Intramolecular addition of an O-methyl C(sp3)?H bond across a carbon-carbon double bond occurs in the iridium-catalyzed reaction of methyl 2-(propen-2-yl)phenyl ethers. The Ir/(S)-DTBM-SEGPHOS catalyst promotes the reaction efficiently in toluene at 110–135 °C to afford 3,3-dimethyl-2,3-dihydrobenzofurans. Enantioselective C(sp3)?H addition is achieved in the reaction of methyl 2-(1-siloxyethenyl)phenyl ethers, affording enantioenriched 3-hydroxy-2,3-dihydrobenzofuran derivatives with up to 96% ee. (Figure presented.).
- Ohmura, Toshimichi,Kusaka, Satoshi,Torigoe, Takeru,Suginome, Michinori
-
supporting information
p. 4448 - 4453
(2019/09/16)
-
- Ultrasound-assisted synthesis and antimicrobial activity of tetrazole-based pyrazole and pyrimidine derivatives
-
New tetrazole-based pyrazole and pyrimidine derivatives were synthesized by an ultrasound irradiation method. All compounds were characterized by infrared spectroscopy (IR), 1H nuclear magnetic resonance (NMR), 13C NMR, mass spectrometry (MS) and elemental analysis and assessed in vitro for their efficacy as antimicrobial agents against four bacteria (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa) and two fungi (Candida albicans, Aspergillus Niger). Compounds 8a, 8e, 9a, 9b and 9e show potent activity against the tested strains compared to the reference drugs chloramphenicol and clotrimazole.
- Dofe, Vidya S.,Sarkate, Aniket P.,Shaikh, Zarina M.,Gill, Charansingh H.
-
-
- Reusable and efficient polyvinylpolypyrrolidone-supported triflic acid catalyst for acylation of alcohols, phenols, amines, and thiols under solvent-free conditions
-
Abstract: A triflic acid-functionalized polyvinylpolypyrrolidone was prepared and fully characterized by FT-IR, TGA, and SEM. This super acidic solid catalyst shows high catalytic activity for selective acylation of alcohols, phenols, amines, and thiols with anhydrides under solvent-free conditions at room temperature. In addition, this method features an easy to handle solid super acid catalyst and an operationally simple procedure, affording the desired acylated products in excellent yields. Graphical abstract: [Figure not available: see fulltext.].
- Tajbakhsh, Mahgol,Tajbakhsh, Mahmoud,Khaksar, Samad,Gazvini, Helia Janatian,Heidary, Marzieh
-
p. 1117 - 1122
(2017/05/10)
-
- Synthesis, antimicrobial activity and anti-biofilm activity of novel tetrazole derivatives
-
In the development of antimicrobial agents, we designed and synthesized novel tetrazole derivatives. The structures of compounds 6a-f and 7a-f were characterized by IR, 1H NMR, 13C NMR, MS and elemental analysis. These compounds were tested for their antimicrobial activity against a series of strains Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa and for antifungal activity against the strains Candida albicans, Candida glabrata, and Candida tropicalis. Compounds 6e, 6f, 7a, and 7f exhibit potent antimicrobial activities compared to the reference drugs streptomycin and miconazole. Tetrazole derivatives 7a-f also inhibit biofilm formation and compound 7f exhibits best anti-biofilm activity with a biofilm inhibitory concentration (BIC) as low as 0.9 μm.
- Dofe, Vidya S.,Sarkate, Aniket P.,Kathwate, Santosh H.,Gill, Charansingh H.
-
p. 325 - 330
(2017/08/18)
-
- Vitamin B1 supported on silica-encapsulated γ-Fe 2O3 nanoparticles: Design, characterization and application as a greener biocatalyst for highly efficient acylation
-
A new magnetic catalyst was synthesized by the immobilization of vitamin B1 (thiamine hydrochloride) on the surface of silica-encapsulated γ-Fe2O3 nanoparticles. Its capability was evaluated in the acylation of alcohols and phenols with acetic anhydride under solvent-free conditions and afforded the desired products in high yield. This novel magnetic organocatalyst could be separated from the reaction vessel by use of an external magnet and recovered 5 times without a significant loss of its activity. The amount of loaded vitamin B1 on the silica-encapsulated γ-Fe2O3 was assigned by TGA and confirmed by back titration. Availability, cheapness and low toxicity are reasons associated with the utilization of vitamin B1 as a catalyst. The catalyst has been characterized by FT-IR, XRD, SEM, VSM and TG/DTA. The Royal Society of Chemistry.
- Azizi, Kobra,Heydari, Akbar
-
p. 8812 - 8816
(2014/03/21)
-
- Steric control of site selectivity in the Pd-catalyzed C-H acetoxylation of simple arenes
-
This report describes the use of an oxidant and a ligand to control site selectivity in the Pd(OAc)2-catalyzed C-H acetoxylation of simple arenes. The use of MesI(OAc)2 as the terminal oxidant in combination with acridine as the ligand results in primarily sterically controlled selectivity. In contrast, with Pd(OAc)2 as the catalyst and PhI(OAc)2 as the oxidant, electronic effects dominate the selectivity of arene C-H acetoxylation.
- Cook, Amanda K.,Emmert, Marion H.,Sanford, Melanie S.
-
supporting information
p. 5428 - 5431
(2013/11/19)
-
- L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate (supported on silica gel) as a new and efficient catalyst for acylation of alcohols, phenols and amines under solvent-free conditions
-
In the present work, L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate, supported on silica gel was prepared and characterized by Mass spectroscopy, 1H NMR, 13CNMR, FT IR and elemental analysis (CHN) methods. This heterogenized catalyst can be used as an efficient catalyst for the acylation of alcohols, phenols, and amines with acetic anhydride under mild and solvent-free conditions. Simple work-up, stability of the catalyst, nontoxicity and good to high yields are the advantages of this work.
- Hajjami, Maryam,Ghorbani-Choghamarani, Arash,Khani, Zahra
-
p. 324 - 329
(2013/07/26)
-
- Use of transesterified 1,3-diketoesters in the synthesis of trisubstituted pyrazoles and their biological screening
-
Starting from 2-acetylbenzofuran derivatives 1a-d, methyl/ethyl 4-substituted/unsubstituted benzofuran-2-yl)-2,4-dioxobutanoate 2a-d and 3a-d have been synthesized by Claisen's condensation reaction with diethyloxalate. The transesterified product, 1,3-diketoester 2a-d on condensation with phenyl hydrazine undergo cyclization to afford the corresponding methyl 5-(substituted/unsubstituted benzofuran-2-yl)-1-phenyl- 1H-pyrazole-3- carboxylate 4a-d, which upon further condensation with hydrazine hydrate yielded 5- (substituted/unsubstituted benzofuran-2-yl)-1-phenyl-1H-pyrazole-3- carbohydrazide 5a-d. The structures of the newly synthesized compounds 2a-d, 3a-d, 4a-d and 5a-d were characterized by their elemental analysis and spectral studies such as IR, 1H NMR, 13C NMR and MS. All the synthesized compounds were screened for their antimicrobial activity. Most of the synthesized compounds showed high sensitivity against the selected bacteria and fungi at various concentrations.
- Siddiqui, Naqui-Jahan,Idrees, Mohammad,Khati, Niraj T.,Dhonde, Madhukar G.
-
-
- Solvent-free acetylation and tetrahydropyranylation of alcohols catalyzed by recyclable sulfonated ordered nanostructured carbon
-
Rapid and practical green acetylation and tetrahydropyranylation routes of structurally diverse alcohols and phenols were applied under solvent-free reaction conditions providing excellent yields, using catalytic amounts of environmentally friendly sulfonated ordered nanoporous carbon (CMK-5-SO 3H). Non-toxic nature of the catalyst, its easy handling, recovery and reusability, and the absence of any solvent characterize the presented procedures as efficient methods. These procedures provide methods for the separation of the product by simple filtration.
- Zareyee, Daryoush,Alizadeh, Parastoo,Ghandali, Mohammad S.,Khalilzadeh, Mohammad A.
-
p. 713 - 721
(2013/07/26)
-
- H6GeMo10V2O40·16H 2O nanoparticles prepared by hydrothermal method: A new and reusable heteropoly acid catalyst for highly efficient acetylation of alcohols and phenols under solvent-free conditions
-
A new Keggin-type heteropoly acid, namely decamolybdodivanadogermanic acid (H6GeMo10V2O40·16H 2O), with nanosized particles (5-8 nm), has been synthesized by a hydrothermal method and characterized by elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-Visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and potentiometric titration. H6GeMo10V2O40·16H 2O revealed high catalytic activity for acetylation of various alcohols and phenols with acetic anhydride at room temperature (298 ± 2 K) and under solvent-free conditions. The catalyst can be easily recovered and used repeatedly for five cycles with a slight loss of activity. The catalytic activity of H6GeMo10V2O40· 16H2O was higher than that of other Keggin-type heteropoly acids, such as H3PW12O40, H3PMo 12O40 and H4SiW12O40.
- Farhadi, Saeid,Zareisahamieh, Reza,Zaidi, Masoumeh
-
experimental part
p. 1323 - 1332
(2012/04/04)
-
- Spinel-type zinc aluminate (ZnAl2O4) nanoparticles prepared by the co-precipitation method: A novel, green and recyclable heterogeneous catalyst for the acetylation of amines, alcohols and phenols under solvent-free conditions
-
Zinc aluminate (ZnAl2O4) nanoparticles with an average particle size of about 8 nm were easily prepared by the co-precipitation method using aqueous ammonia solution as the precipitating agent. This nanosized spinel-type oxide was characterized by TGA, XRD, FT-IR, TEM, and surface area measurement and used as the heterogeneous catalyst for the acetylation reaction. Efficient acetylation of various amines, alcohols and phenols was carried out over ZnAl2O4 nanoparticles using acetic anhydride and/or acetyl chloride as the acetylating agents at room temperature without the use of a solvent. The method is highly selective, allowing the alcoholic hydroxyl group to be protected while the phenolic hydroxyl group remains intact, and the amine group can be acetylated in the presence of the hydroxyl group. This method is fast and has a high yield. It is also clean, safe, cost effective, compatible with substrates that have other functional groups and very suitable for practical organic synthesis. In addition, the catalyst can be reused without significant loss of activity. Indeed, the catalytic activity of the ZnAl2O4 nanoparticles is higher than that of bulk ZnAl2O4.
- Farhadi, Saeid,Panahandehjoo, Somayeh
-
scheme or table
p. 293 - 302
(2010/09/04)
-
- Highly efficient dynamic kinetic resolution of secondary aromatic alcohols with low-cost and easily available acid resins as racemization catalysts
-
A new and efficient dynamic kinetic resolution (DKR) process of secondary aromatic alcohols was developed with acid resins as racemization catalysts. Acid resin CD8604 was shown to have excellent racemization activity and good biocompatibility. When employing CD8604 and complex acyl donors as racemization catalyst and acyl donor, respectively, enantiomerically pure aromatic acetate was obtained with excellent yield and ee values through the DKR process. It is noteworthy that the system could be reused more than 10 times with little loss of yield and ee value.
- Cheng, Yongmei,Xu, Gang,Wu, Jianping,Zhang, Chensheng,Yang, Lirong
-
supporting information; experimental part
p. 2366 - 2369
(2010/06/13)
-
- Rapid and efficient method for acetylation of alcohols and phenols with acetic anhydride catalyzed by silica sulfate
-
A rapid and efficient method is described for acetylation of a series of alcohols and phenols with acetic anhydride catalyzed by silica sulfate solid acid at room temperature or at refluxing temperature in excellent yield. Copyright Taylor & Francis Group, LLC.
- Jin, Tong-Shou,Zhao, Ying,Liu, Li-Bin,Chen, Zhuo,Li, Tong-Shuang
-
p. 1221 - 1227
(2007/10/03)
-
- Silica gel-supported phosphotungstic acid (PTA) catalysed acylation of alcohols and phenols with acetic anhydride under mild reaction conditionst
-
Phosphotungstic acid, which is commercially available, practically and efficiently catalyses the acylation of a series of alcohols and phenols with acetic anhydride at room temperature of at refluxing temperature.
- Jin, Tong-Shou,Xiao, Jin-Chong,Wang, Zhen-Hua,Li, Tong-Shuang
-
p. 412 - 414
(2007/10/03)
-
- Photodegradation of Dichlorprop and 2-Naphthoxyacetic Acid in Water. Combined GC-MS and GC-FTIR Study
-
We have examined the photochemical transformations of dichlorprop (1) and 2-naphthoxyacetic acid (2) in aqueous solution, by means of combined GC-MS and GC-FTIR analysis. Photolysis of 1 under oxygen atmosphere led to 2-chlorophenol (5), 2,4-dichlorophenol (6), 4-chlorophenol (7), 2,4-dichlorophenyl acetate (8), the lactone of 2-(4-chloro-2-hydroxyphenoxy)propionic acid (9), and 2-(2-chlorophenoxy)propionic acid (10). Irradiation under argon atmosphere led again to 5, 6, 7, and 10 together with 2,4-dichlorophenyl ethyl ether (11). Photolysis of 2 under aerobic conditions gave β-naphthol (12), together with minor amounts of 2-hydroxy-1-naphthaldehyde (13) and naphtho [2,1-b]furan-2(1H)-one (14). Under argon atmosphere only 12 and 14 were detected. Therefore, the most general processes were photolytic cleavage of the aryl-halogen bond (route i) and the aryloxy-carbon bond (route ii). Similar photodegradation pathways had been previously observed for 2,4-D and 4-CPA and were confirmed in this work. The formation of 8, 11, and 13 must occur via cleavage of the carbon-carbon bond a to the carboxy group (route iii). Formation of this type of photoproducts in phenoxyalkanoic acid pesticides is unprecedented. Its structure was further assessed by alternative synthesis.
- Climent, Maria Jose,Miranda, Miguel A.
-
p. 1916 - 1919
(2007/10/03)
-
- Structure-reactivity correlations for reactions of substituted phenolate anions with acetate and formate esters
-
The reactions of substituted phenolate anions with m-nitrophenyl, p-nitrophenyl, and 3,4-dinitrophenyl formates follow nonlinear Br?nsted-type correlations that might be taken as evidence for a change in the rate-limiting step of a reaction that proceeds through a tetrahedral addition intermediate. However, the correlation actually represents two different Br?nsted lines that are defined by meta- and para-substituted phenolate anions and by meta- and para-substituted o-chlorophenolate anions. A concerted mechanism for both acetyl- and formyl-transfer reactions is supported by the absence of a detectable change in the Br?nsted slope at ΔpK = 0 for the attacking and leaving phenolate anions within each class of Br?nsted correlations. Regular increases in the dependence of log k on the pKa of the nucleophile with increasing pKa of the leaving group correspond to a positive interaction coefficient pxy = ?β1g/?(pKnuc) = ?βnuc/?(pK1g). The observation of two different Br?nsted lines for the reactions of substituted phenolate anions with phenyl acetates is attributed to a steric effect that decreases the rate of reaction of substituted o-chlorophenolate anions by 25-50%. The reactions of meta- and para-substituted phenolate and o-chlorophenolate anions with substituted phenyl acetate esters follow values of βnuc = 0.53-0.66 and -β1g = 0.50-0.63. The reactions of meta- and para-substituted phenolate anions with formate esters are ~ 103 times faster and follow smaller values of βnuc = 0.43-0.64 and -β1g = 0.31-0.48. However, the reactions of meta- and para-substituted o-chlorophenolate anions with the same formate esters follow larger values of βnuc = 0.63-0.90 and -β1g = 0.46-0.90. The large values of βnuc and -β1g for the reactions of substituted o-chlorophenolate anions with formate esters may arise from destabilization by the o-chloro group of a stacking interaction that is present in the transition state for reactions of formate esters, but not acetate esters.
- Stefanidis, Dimitrios,Cho, Sayeon,Dhe-Paganon, Sirano,Jencks, William P.
-
p. 1650 - 1656
(2007/10/02)
-
- An Open Transition State in Carbonyl Acyl Group Transfer in Aqueous Solution
-
The second-order rate constants have been measured for the reaction of substituted phenolate ions with 2,4-dinitrophenyl acetate, 2,4-dinitrophenyl 4-methoxy-2,6-dimethylbenzoate and acetic anhydride in aqueous solution at 25 deg C.The data are over a wide range of phenolate ion basicity and obey good Broensted equations which have βnuc values of, respectively, 0.57 +/- 0.03, 0.15 +/- 0.07 and 0.59 +/- 0.05.The principal conclusion of this work is that the identity reaction of 2,4-dinitrophenolate ion with 2,4-dinitrophenyl 4-methoxy-2,6-dimethylbenzoate has anopen transition state, namely one with very weak bonds to entering and departing ligands.The transition state possesses a Kreevoy tightness parameter (τ) of 0.18.The open transition state arises from the stabilising effect of the acyl group substituents on the benzoylium ion and their destabilising effect on the putative tetrahedral intermediate as well as the weak basicities of the nucleophile and nucleofuge.This is the first example of an open transition state in an acyl group transfer which does not require the assistance of a negatively charged internal nucleophile.The data for 2,4-dinitrophenyl acetate may be employed to calculate an identity rate constant (kii) for the reaction of 2,4-dinitrophenolate ion with the ester.This data may be fitted to a theoretical Lewis-Kreevoy plot (log kii vs. pKi) possessing both positive and negative values of βii (slope of the line).Microscopic medium effects place a limit to the accuracy of predictions of rate constants, including kii, from linear free energy relationships.
- Ba-Saif, Salem A.,Colthurst, Matthew,Waring, Mark A.,Williams, Andrew
-
p. 1901 - 1908
(2007/10/02)
-