Current Organocatalysis - Volume 9, Issue 3, 2022

This work aims to provide an overview of the applications of succinimide-based reagents for the promotion of some important organic reactions, including protection and multicomponent ones. Mild reaction conditions, simple and easy work-up procedure, high to excellent yields, stability, and reusability of the catalysts are noteworthy advantages of these methods.

Background: Curcuma longa L. is an herbaceous plant of the Zingiberaceae family. curcumin and its derivatives possess a vast variety of biological activities like antimicrobial, antioxidant, anti-inflammatory, antimalarial, antirheumatic, etc. Looking into the biological significance of curcumin and its derivatives, we have decided to synthesize novel derivatives of curcumin and their coordinated Copper (II) complexes and evaluate their pharmacological activities like antioxidant, antibacterial, etc. Methods: Targeted derivatives of curcumin were prepared in good yield (95%) by the condensation reaction of carbohydrazide (1), and curcumin (2), in the presence of copper salts using classical heating methods in the presence of absolute ethanol. Results: The targeted derivatives of curcumin were evaluated for their collaborative antimicrobial activity against gram-positive and gram-negative bacterial strains. The zone of inhibition was measured by considering the disc diffusion method. In vitro minimum inhibitory concentrations of targeted compounds were measured using the broth micro-dilution method. In addition to this, the in vitro antioxidant activity of target compounds was also evaluated by adopting the DPPH method using ascorbic acid as a standard substance. Most of the compounds showed fascinating antibacterial and antioxidant activities in contrast to pure curcumin. Conclusion: In conclusion, the present work explains the synthesis, characterization, and evaluation of biological activities of novel derivatives of curcumin and their coordinated Copper (II) complexes. All the targeted compounds were screened for their pharmacological activities against selected human pathogenic bacteria. The antioxidant activity of the synthesized compounds was also evaluated against DPPH and ascorbic acid standard substances. Among the designed molecules, most of the compounds showed fascinating antibacterial and antioxidant activities as compared to pure curcumin.

Background: Nanocatalysts exhibit several applications in the synthesis of many industrially important organic compounds. They manifest fascinating physical and chemical properties which can be exploited in their catalytic applications. Methods: A magnetically recyclable Ag@Fe2O3 core-shell structured nanocatalyst was synthesized by a simple sol-gel technique and characterized by X-ray diffraction spectroscopy, field emission scanning electron microscope, high-resolution transmission electron microscopy, fourier transform infrared spectroscopy, vibrating sample magnetometer etc. Nanocatalyst was found to be a highly efficient heterogeneous catalyst for the synthesis of 2-aryl, benzimidazoles and benzothiazoles via one-pot condensation of aromatic aldehydes and 1, 2-phenylenediamine, and 2-aminothiophenol. Results: Fe2O3 nanocatalyst provides rapid conversion of the substrate into the desired product at room temperature within just 5-18 min in the presence of C2H5OH with good to excellent yield. The combination of Ag core with magnetic Fe2O3 shell improves efficiency, stability, magnetic recovery, and reusability compared to the individual nanoparticles. Conclusion: The synthetic protocol is featured high yield, mild conditions, and simple work-up. Magnetic recovery of the catalyst from reaction systems and its reusability for several runs without loss of catalytic activity are additional advantages.

Background: In this work, a series of pyridinium-based ionic liquids (PBILs) were synthesized. Methods: Pyridinium-based ionic liquids (PBILs) were synthesized through a simple method, which were initially evaluated as catalysts for the synthesis of tetrahydro[b]benzopyran derivatives via a one-pot three-component reaction involving aldehydes, malononitrile, and dimedone. Results: The PBILs perform well in this condensation reaction, especially 1-methylpyridin-1-ium dimethyl phosphate (MPDMP). Conclusion: The advantages of this procedure are good yields, short reaction time, simplicity of implementation, and inexpensive starting materials.

Background: In recent times, there has been on-going interest in developing convenient and environmentally friendly synthetic methods in organic chemistry. The use of ionic liquid catalysts in organic synthesis is a developing area that allows reactions to be run at low temperatures and without solvents. Literature overview revealed that room temperature supported ionic liquid catalysis is a developing field in catalytic science with huge application in organic synthesis. Hence in this current article, our focus is on the one-pot synthesis of arylidene derivatives with the use of ([bmim] OH) ionic liquid. Objective: We describe here the use of an ionic liquid catalyst, 1-n-butyl-3-methylimidazolium hydroxide, [bmim] OH), in the convenient one pot synthesis of arylidene derivatives by the reaction of the active methylene compound, malononitrile, with pyrazole aromatic aldehydes under microwave irradiation. Methods: The functionalized ionic liquid, 1-n-butyl-3-methylimidazolium hydroxide ([bmim] OH), catalyzed Knoevenagel condensation reactions of pyrazole aromatic aldehydes with active methylene compound malononitrile carried out under microwave irradiation. The reaction progress was monitored by thin layer chromatography and the synthesized compounds were further characterized by NMR spectroscopy. Results: This proposed work demonstrates the utility of the use of the ionic liquid catalyst [bmim] OH, in the suitable, high yield (80-95%) microwave assisted reactions of pyrazole aromatic aldehydes with the active methylene compound, malononitrile. Conclusion: An eco-friendly synthesis of pyrazole derivatives has been demonstrated using ([bmim] OH) ionic liquid as a catalyst for the Knoevenagel condensation reactions of pyrazole aromatic aldehydes and malononitrile with microwave irradiation. The advantages of this green method are its convenience, mild reaction conditions, and high product yields (80-95%).

Background: Nicotine (NIC) is a lipid-soluble alkaloid found predominantly in tobacco products, including cigarettes, cigars, and oral tobacco products such as snuff and chewing tobacco. Since nicotine substrate is the major constituent of tobacco smoke, it may cause negatively impacted problems for human healthcare, which keeps many users hooked. Methods: A spectrophotometric technique has been applied to investigate the kinetics of reductoin hexachloroiridate (IV) as an inert one-equivalent oxidant by carcinogenic nicotine (NIC) in aqueous perchlorate solutions. Results: First-order in [IrCl6]²- and fractional-first-order concerning the nicotine concentration has been revealed. Kinetic evidence for forming a 1:1 intermediate complex between the NIC and [IrCl6]2- before the rate-determining step was confirmed. Conclusion: The ionization constants of nicotine were evaluated from the kinetic data and are 8.57x10-4 and 4.57 x 10-4 moldm-3 at an ionic strength of 0.5 moldm-3 and 30°C and 40°C, respectively. The activation parameters have been deduced from the kinetic results of the temperature dependence of rate constants. A plausible reaction mechanism for the redox reaction is suggested and discussed. Nicotinic acid (Vitamin B3) was formed as an oxidation product of nicotine oxidation.