The development of phosphinoamine–Pd(II)–imidazole complexes: implications in room‐temperature Suzuki–Miyaura cross‐coupling reaction

The reaction of N‐methylimidazole (N‐MeIm) and N‐butylimidazole (N‐BuIm) with the complexes [PdCl₂(PPh₂py–P,N)] and [PdCl₂(PPh₂Etpy–P,N)] in the presence of NH₄PF₆ under N₂ at room temperature afforded four new cationic Pd(II) complexes [PdCl(PPh₂py–P,N)(N‐MeIm)](PF₆) ( 1 ), [PdCl(PPh₂py–P,N)(N‐BuIm)](PF₆) ( 2 ), [PdCl(PPh₂Etpy–P,N)(N‐MeIm)](PF₆) ( 4 ) and [PdCl(PPh₂Etpy‐P,N)(N‐BuIm)](PF₆) ( 5 ) in good yields, where PPh₂py is 2‐(diphenylphosphino)pyridine and PPh₂Etpy is 2‐{2‐(diphenylphosphino)ethyl}pyridine). The complexes were fully characterized. The catalytic activities of these complexes were investigated for Suzuki–Miyaura cross‐coupling reactions at room temperature. Complex 2 exhibited excellent activity compared to other analogs. Copyright © 2013 John Wiley & Sons, Ltd.     

Iron(0), rhodium(I) and palladium(II) complexes with p‐(N,N‐dimethylaminophenyl) diphenylphosphine and the application of the palladium complex as a catalyst for the Suzuki–Miyaura cross‐coupling reaction

The reaction of p‐(N,N‐dimethylaminophenyl)diphenylphosphine [PPh₂(p‐C₆H₄NMe₂)] with [Fe₃(CO)₁₂], [Rh(CO)₂Cl]₂ and PdCl₂ resulted in three new mononuclear complexes, {Fe(CO)₄[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1a ), trans‐{Rh(CO)Cl[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 2 ) and trans‐{PdCl₂[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 3 ), respectively. A small amount of dinuclear nonmetal‐metal bonded complex, {Fe₂(CO)₈[µ‐(P,N)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1b ), was also isolated as a side product in the reaction of [Fe₃(CO)₁₂]. The complexes were characterized by elemental analyses, mass, IR, UV–vis, ¹H, ¹³C (except 1b) and ³¹P{¹H} NMR spectroscopy. The Pd complex 3 effectively catalyzes the Suzuki–Miyaura cross‐coupling reactions of aryl halides with arylboronic acids in water–isopropanol (1:1) at room temperature. Excellent yields (up to 99% isolated yield) were achieved. The effects of different solvents, bases, catalyst quantities were also evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

Green Synthesis of Tetraalkylammonium Tribromide using Cerium(IV) Ammonium Nitrate (CAN) as Oxidant

Cerium(IV) ammonium nitrate (CAN) mediates oxidation of tetraalkylammonium bromide to tetraalkylammonium tribromide in greener reaction conditions using water as solvent. The procedure is simple, convenient, and environmentally benign for the synthesis of tetraalkylammonium tribromide with great yields.     

InCl3-Catalyzed,Three-Component Reactions for the Synthesis of Some Novel Functionalized/Annulated Barbituric Acids

Some novel 5-aminoalkylbarbituric acids and corresponding chromene derivatives were synthesized via a one-pot, three-component Mannich reaction starting from 1,3-dimethylbarbituric acid, arylaldehydes, and amines.     

Aza-Michael Addition of Amines to α,β-Unsaturated Compounds Using Molecular Iodine as Catalyst

Aza-Michael adducts are obtained in very good yields by the conjugate addition of aliphatic amines to α,β-unsaturated compounds using molecular iodine as catalyst in dichloromethane at room temperature. Aromatic amines were found to be reactive under reflux in toluene.     

Effect of E × B electron drift and plasma discharge in dc magnetron sputtering plasma

Study of electron drift velocity caused by Etimes B motion is done with the help of a Mach probe in a dc cylindrical magnetron sputtering system at different plasma discharge parameters like discharge voltage, gas pressure and applied magnetic field strength. The interplay of the electron drift with the different discharge parameters has been investigated. Strong radial variation of the electron drift velocity is observed and is found to be maximum near the cathode and it decreases slowly with the increase of radial distance from the cathode. The sheath electric field, E measured experimentally from potential profile curve using an emissive probe is contributed to the observed radial variation of the electron drift velocity. The measured values of the drift velocities are also compared with the values from the conventional theory using the experimental values of electric and magnetic fields. This study of the drift velocity variation is helpful in providing a useful insight for determining the discharge conditions and parameters for sputter deposition of thin film.     

Graphene Oxide Nanosheets at the Water–Organic Solvent Interface: Utilization in One‐Pot Adsorption and Reactive Extraction of Dye Molecules

Graphene oxide (GO) is amphiphilic in nature, due to its structure, which consists of hydrophilic oxygen‐containing functional groups and a hydrophobic basal plane of polyaromatic benzene rings. Due to this amphiphilicity, GO can create stable bubbles at water–organic solvent interfaces. In this study, the formation of bubbles at aqueous–organic interfaces in the presence of GO is investigated with different organic solvents. Bubble formation and transfer of GO from water to the organic phase is more prominent in aromatic solvents compared to aliphatic solvents, due to π–π interactions. Maximum transfer of GO from the aqueous to the organic phase is achieved at pH 2, and decreases with rising pH of the aqueous phase. Based on this property, and the ability of GO to adsorb cationic and anionic dye molecules, its application as a carrier for reactive extraction of cationic and anionic dye molecules is explored in toluene, kerosene, and carbon tetrachloride at pH 2 and 25 °C. The kinetics of the adsorption of the dyes onto GO nanosheets that takes place in the aqueous phase is also evaluated with different models, and a pseudo‐second‐order (linear) model is found to be the best fit. The adsorption isotherm data are also analyzed with different isotherm models. The electrostatic interaction and π–π interaction between the dye molecules and GO nanosheets leads to dye extraction of up to 98.2 % using this technique. The dye extraction is maximum in toluene and at low dye concentration.     

C-C bond cleavage: Metal-free-catalyzed reaction of Betti bases with various heterocycles under microwave irradiation

The reaction of Betti bases with various heterocycles in the presence of p-toluenesulphonic acid (PTSA) under microwave irradiation gives bis(heterocycle)methanes through benzyl transfer. The reaction proceeds via the cleavage of C-N bond followed by C-C bond. The metal-free cleavage of C-C bond, which is in fact a C-dearylation, is rarely reported in the literature.     

Green Synthetic Approach: An Efficient Eco-Friendly Tool for Synthesis of Biologically Active Oxadiazole Derivatives

Green synthetic protocol refers to the development of processes for the sustainable production of chemicals and materials. For the synthesis of various biologically active compounds, energy-efficient and environmentally benign processes are applied, such as microwave irradiation technology, ultrasound-mediated synthesis, photo-catalysis (ultraviolet, visible and infrared irradiation), molecular sieving, grinding and milling techniques, etc. Thesemethods are considered sustainable technology and become valuable green protocol to synthesize new drug molecules as theyprovidenumerous benefits over conventional synthetic methods.Based on this concept, oxadiazole derivatives are synthesized under microwave irradiation technique to reduce the formation of byproduct so that the product yield can be increased quantitatively in less reaction time. Hence, the synthesis of drug molecules under microwave irradiation follows a green chemistry approach that employs a set of principles to minimize or remove the utilization and production of hazardous toxic materials during the design, manufacture and application of chemical substances.This approach plays a major role in controlling environmental pollution by utilizing safer solvents, catalysts, suitable reaction conditions and thereby increases the atom economy and energy efficiency. Oxadiazole is a five-membered heterocyclic compound that possesses one oxygen and two nitrogen atoms in the ring system.Oxadiazole moiety is drawing considerable interest for the development of new drug candidates with potential therapeutic activities including antibacterial, antifungal, antiviral, anticonvulsant, anticancer, antimalarial, antitubercular, anti-asthmatic, antidepressant, antidiabetic, antioxidant, antiparkinsonian, analgesic and antiinflammatory, etc. This review focuses on different synthetic approaches of oxadiazole derivatives under microwave heating method and study of their various biological activities.     

Raman spectroscopy for study of interplay between phonon confinement and Fano effect in silicon nanowires

A combined effect of doping (type and species) and size on Raman scattering from silicon (Si) nanowires (NWs) has been presented here to study interplay between quantum confinement and Fano effects. The SiNWs prepared from low doping Si wafers show only confinement effect, as evident from the asymmetry in the Raman line‐shape, irrespective of the doping type. On the other hand SiNWs prepared from wafer with high doping shows the presence of electron–phonon interaction in addition to the phonon confinement effect as revealed from the presence of asymmetry and antiresonence in the corresponding Raman spectra. This combined effect induces an extra asymmetry in the lower energy side of Raman peak for n‐type SiNWs whereas the asymmetry flips from lower energy side to the higher energy side of the Raman peak in p‐type SiNWs. Such an interplay can be represented by considering a general Fano‐Raman line‐shape equation to take care of the combined effect in SiNWs. Copyright © 2015 John Wiley & Sons, Ltd.