China 
Africa 
Explore chapters and articles related to this topic
Ligand-Free Palladium Nanoparticles Catalyzed Hiyama Cross-Coupling of Aryl and Heteroaryl Halides in Ionic Liquids
Published in Tanmoy Chakraborty, Lalita Ledwani, Research Methodology in Chemical Sciences, 2017
Chanchal Premi, Ananya Srivastava, Nidhi Jain
The preformed Pd NPs generated in 1 is now used as catalyst in Hiyama coupling by diluting it with acetonitrile followed by the addition of the arylhalide, trimethoxyphenylsilane, and [bmim]F as activators. The cross-coupling of iodobenzene with trimethoxyphenylsilane and Pd NPs in 1 as catalyst was investigated by using different activators such as TBAF, NaOAc, [bmim]OAc, and [bmim]F. Although the reaction failed to occur with NaOAc, in the presence of TBAF, biphenyl was obtained in 98% yield (Table 7.2, entry 2), and 2 and 3 (2.0 equiv.) afforded the product in 98 and 72% yield, respectively. This suggests that fluorine-based 2 is a better desilyate than oxygen-based 3 (Table 7.2, entries 7 and 8). Optimization of the reaction conditions for the Hiyama coupling of iodo-, bromo-, and chlorobenzene with trimethoxyphenylsilane was carried out by varying the activator, catalyst ratio, time, and temperature (Table 7.2). Optimization of the reaction conditions showed that trimethoxyphenylsi-lane (2 equiv.) and Pd(OAc)2 (4 mol%) in 1 acetonitrile solution were required for the aryl iodide (1 equiv.) to yield 98% of the coupled product at 70°C over 8 h.
Aqueous Dispersions of Metallic Nanoparticles
Published in Victor M. Starov, Nanoscience, 2010
Alexander Kamyshny, Shlomo Magdassi
Suzuki cross-coupling reaction between iodobenzene and phenylboronic acid in aqueous medium was found to be effectively catalyzed by Pd nanoparticles stabilized by PVP [30,185,322]. PVP- and polyacrylate-stabilized Pt nanoparticles catalyze the electron transfer reaction between hexacyanoferrate( III) and thiosulfate ions [30,244–246] and poly-(N-vinylformamide)-stabilized Pt nanoparticles catalyze hydrogenation of allyl alcohol [323]. Reduction of dyes (methylene blue, phenosafranin, fluorescein, 2,7-dichlorofluorescein, eosin, and rose bengal) was shown to be accelerated by Pd nanoparticles stabilized by various surfactants (CTAB, SDS, Triton X-100), and catalytic selectivity can be tuned by a proper selection of the reducing agent and surfactant [132]. Pd nanoparticles stabilized by PEG-6000 catalyze the Hiyama cross-coupling reactions between arylsiloxanes and aryl bromides [324]. Cu nanoparticles (nanorods) were shown to be a selective catalyst for oxidative phenol coupling between two 2-naphthol moieties [193]. Colloidal PVP-stabilized Ag was reported to catalyze oxidation of ethylene by oxygen in ethanol/water (1 : 1) mixture [325]. Iron, palladized iron, and palladized gold nanoparticles were shown to effectively catalyze dechlorination of dichloroethene and polychlorinated biphenyls in water and can be considered as promising catalysts for development of groundwater remediation technologies [143,326]. Hydrogenation of vinyl acetate catalyzed by Pt nanoparticles stabilized by dodecyltrimethyl ammonium chloride and PVP was reported in Ref. [327]. Hydrogenation of alkenes was demonstrated to be catalyzed by Rh nanoparticles stabilized by trisulfonated benzene derivatives in biphasic medium (aqueous phase contained recyclable catalyst, while the organic phase was liquid alkene) [328,329]. PVP-stabilized Ag nanoparticles were found to catalyze photodecomposition of phenazine and acridine in water–methanol solution [330].
Structural characterization of ((9-fluorenylidene) (ferrocenyl)methyl)palladium iodide as the catalytic intermediate in the synthesis of 9-(ferrocenyl (ferrocenylethynyl)methylene)-9H-fluorene
Published in Journal of Coordination Chemistry, 2022
2,2′-Oxybis(iodobenzene) (9) (170 mg, 0.416 mmol), [Pd2(dba)3] (28 mg, 6 mol%-Pd), dppf (34 mg, 6 mol%), and CuI (5 mg, 6 mol%) were suspended in 25 mL of a 1:1 THF/NEt3 mixture and degassed with a nitrogen flow for 5 min. Ethynylferrocene (2) (190 mg, 0.905 mmol) was added and the mixture was stirred at 60 °C for 18 h. The mixture was washed with acidified ice water and extracted with diethyl ether until the organic phases remained colorless. The crude material was passed through a plug of silica followed by removal of all volatiles in vacuo. Purification via column chromatography (silica, 3.5 × 15 cm) with a 98:2 hexane/diethyl ether mixture gave the compound as the second orange fraction. The first fraction contained a mixture of diferrocenylbutadiyne and mono-(1-iodo-2-(2-(ferrocenylethynyl)phenoxy) benzene) and hydrodehalogenated species (1-phenoxy-2-(ferrocenylethynyl)benzene), from which the latter crystallized.
Visible-light promoted serendipitous synthesis of 3,5-diaryl-1,2,4-thiadiazoles via oxidative dimerization of thiobenzamides
Published in Journal of Sulfur Chemistry, 2022
Various approaches towards the synthesis of 1,2,4-thiadiazoles have been explored during the past years involving the cycloaddition of nitrile sulfides with ethyl cyanoformate [14], N-arylbenzamidines with isothiocyanate [15], dimerization of aryl nitriles with ammonium sulfide and 2,4,6-trichloro-1,3,5-triazine (TCT)–DMSO in an ionic liquid [16]. The oxidative dimerization of thioamides is one of the most common methods employed for the synthesis of 1,2,4-thiadiazoles. A variety of oxidizing agents, such as N-bromosuccinimide (NBS) [17], ceric ammonium nitrate (CAN) [18], trichloroisocyanuric acid [19], molecular iodine [20], pentylpyridinium tribromide [21], photoredox catalyst eosin Y [22], molecular oxygen under visible light irradiation [23], and hypervalent iodine reagents namely (diacetoxyiodo)benzene (DIB) or [bis(trifluoroacetoxy)iodo] benzene (BTI) [24], phenyliodine (III) bis(trifluoroacetate), [25] polystyrene-supported iodobenzene diacetate (PIBD) [26], and IBX/TEAB [27] have been employed for oxidative dimerization of thioamides. Although refined from time to time, these reported methods have the demerits like longer reaction time, low yields, harsh reaction conditions, tedious workup, and use of hazardous organic solvents, which leaves scope for further development of new practical synthetic approaches which follow green chemistry principles desirable for the chemical and pharmaceutical industries.
Coordination complexes featuring bidentate κN, κI-8-iodoquinoline
Published in Journal of Coordination Chemistry, 2021
Pramod Dhungana, Pranab K. Nandy, Anwar Hussain, James D. Hoefelmeyer
The electrostatic surface potential of iodobenzene indicates two important features of the iodine atom: (a) the electrostatic surface potential of iodine is roughly similar to that arising from the pi electrons of the phenyl ring and is electron-rich along a ring surrounding the iodine and perpendicular to the C–I bond, (b) there is a “sigma hole” on iodine directly opposite the C–I bond [9]. Ring substituents affect the electrostatic surface potential on the iodine atom within an aryliodide such that electron-withdrawing groups contribute a more positive and larger sigma hole. From this analysis, one might predict coordination of κI-aryliodide will be more favorable with electron-rich aryliodides, and sigma donation from iodine should be directed away from the sigma hole. An important consequence is that metals coordinated to κI-aryliodide ligands should be positioned perpendicular to the C–I bond to avoid the sigma hole [10].