The straightforward co‐precipitation approach was used to effectively manufacture novel silica‐coated magnetic nanoparticles doped with cobalt (Co3O4). These nanoparticles were characterized using Field Emission Scanning Electron Microscopy (FE‐SEM), Energy‐Dispersive X‐ray Spectroscopy (EDS), Wavelength‐Dispersive Spectroscopy (WDX), Powder X‐ray Diffraction Spectroscopy (PXRD), Fourier transform infrared spectroscopy (FT‐IR), Thermo‐gravimetric Analysis (TGA), Inductive coupled plasma‐optical emission spectrometry (ICP‐OES), and Transmission Electron Microscopy (TEM), etc. Intriguingly, the catalytic performance of these nanocrystals for the amines, phenols, alcohols, and thiols acylation processes was examined in solvent‐free conditions, with outstanding yields. These nanoparticles were recycled at least 12 times without losing their catalytic activity.
A new efficient and convenient approach towards the synthesis of pyrazole is described. The α,β-unsaturated cyanoesters were obtained from substituted benzaldehyde and ethyl cyanoacetate by reported methods. 1,5-Disubstituted pyrazoles were synthesized from α,β-unsaturated cyanoester and phenyl hydrazine using sodium ethoxide as a base in the presence of 10 mol % Cu(I) catalyst in high yields within 75-90 min under ultrasound irradiation at 60 ºC. The reaction rate is enhanced tremendously under ultrasound irradiation as compare to conventional methods with improved yields are recorded.
The epoxides were obtained from substituted phenols and epichlorohydrin by reported methods. The regioselective ring opening of epoxides were studied in different solvents by reaction with Grignard’s reagent in presence of dilithium tetrachloromanganate.
The β-amino compounds were synthesized from α,β-unsaturated esters, nitriles and amine using water
as a solvent in the presence of 10 mol % Cu(I) catalyst in high yields within 2-5 min under ultrasound
irradiation at room temperature. The reaction rate was enhanced tremendously under ultrasound irradiation
as compared to conventional methods with improved yields have been recorded.
The regioselective epoxide ring opening at less substituted carbon atom of epoxide were reported by
nucleophiles like heterocyclic amines which gives well known 1,2-difunctionalized amino alcohols.
These are present in many synthetic as well as natural products. The ring opening of epoxide is achieved
by cleavage with amines in presence of copper(0) as a catalyst. It is observed that the lithium
napthalenide reduction of copper(I) produces a highly reactive form of copper(0) that acts as a catalyst
for ring opening of epoxides with an amine.
INTRODUCTION Recently, in organic synthesis, ultrasound technique is widely used. The chemical reaction is enhanced by the ultrasonic irradiation with the help of the process of the acoustic cavitation. The reaction time is shortened by the use of ultrasonic irradiation. In the field of organic chemistry, additional convenience is offered through simple procedure of experiments, increased yields, selectivity and clean reactions of many organic transformations [1-4]. Loomis and Richards [5] first time introduced the chemical effects, which were resulted from ultrasonic irradiation in aqueous medium. There has been report of zinc-Cu(I) ultrasound-mediated conjugate addition reactions developed by Luche & co-workers which involves reactions carried out under aqueous conditions [6,7]. This methodology has been utilized in synthesis of vitamin D analogues. According to a recent trend of synthetic organic chemistry, ultrasound has been emerged as a significant tool to be used for high yield and shorter reaction time in the chemical reactions [8]. In the synthesis of natural products nitrogenous heterocycles and their derivatives are broadly applied [9]. For carbon-nitrogen bond formation, aza-Michael addition of nucleophiles to α,β-unsaturated ketones, esters and nitriles is proved as an effective tool. These reactions are used in synthesis of kinase inhibitor [10], alkaloids [11], β-lactams [12], amino acids [13]. The most popular method for the preparation of 2-pyrazolines refluxing with α,β-unsaturated aldehydes and ketones using phenyl hydrazine in acetic acid [14]. The substituted pyrazolines have biological activities such as antibacterial [15], analgesic
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