Current Organic Chemistry - Volume 26, Issue 12, 2022

In multicomponent reactions (MCRs), highly functionalized compounds can be formed through the reaction between three or more reactants in a one-pot manner. These reactions provide products through the utilization of lesser amounts of energy, time, and effort. MCRs also possess advantages like the generation of lesser waste materials. Fewer resources are needed, high convergence etc. In terms of energy economy and atom economy, MCRs are superior to multistep synthesis. A wide range of products can be acquired by combining the reagents in a variety of ways and thus, MCRs became popular in various fields such as catalysis, pharmaceutical chemistry, material science, agrochemistry, fine chemistry and so on. MCRs obey the principles of green chemistry because these approaches are simple and ecofriendly. MCR is an unrivalled synthetic technique and has been used by chemists at an accelerating rate in recent years. Ruthenium catalysts are cheap in comparison to palladium and rhodium, and generally show high activity. Ru possesses wide-ranging oxidation states due to its 4d75s1 electronic configuration. Numerous organic reactions are catalyzed by ruthenium, which are utilized in forming a wide range of pharmaceuticals and natural products, with biological importance. Minimum amounts of waste materials are formed in most of the ruthenium- catalyzed reactions; hence, ruthenium catalysis paves the way to environmentally benign protocols. Ruthenium chemistry has had a really big impact on organic synthesis in recent years and it is now on par with palladium in terms of relevance. The developments in the field of ruthenium-catalyzed multicomponent reactions are highlighted in this review, covering the literature up to 2021.

The development of the convenient separation processes is a major challenge being examined by scientists and technologists due to its industrial applications. The supported liquid membrane (SLM) technology has been widely employed to separate several species, like permeable gas from binary gaseous mixtures, metal ions, and organic and biological compounds. The main reason for the limited use of SLMs in the industry is their short life and less stability due to the high volatility of traditional organic solvents. Room-temperature ionic liquids (RTILs) are environmentally benign designer salts, exhibit negligible volatility, show good thermal stability, and have remarkable solubility, thus, acting as an alternative solvent to overcome the drawbacks of SLMs. Besides, the high viscosity of ionic liquids (ILs) offers good capillary force, which prevents their flow into membrane pores even under high pressure. Moreover, their tuned properties make them amenable compounds for their immobilization into membrane pores to provide supported ionic liquid membranes (SILMs) with good mechanical strength. In literature (from 2007 to the present), a variety of SILMs have been designed, synthesized, and employed in the field of separation science. This review is mainly focused on the applications of SILMs in the separation of more permeable gases (CO2, O2, CO, H2, and C2H4) from binary gas mixtures as well as the separation of organic compounds (organic acids, alcohols, aromatic hydrocarbons, amines, reactants and products of transesterification reaction, nitrogen- and sulfur-containing aromatic compounds) from distinct mixtures.

Amides are universal in nature. Proteins are polymers (polyamides) whose units are connected by amide (peptide) linkages. Proteins perform innumerable functions in the body. Important synthetic polymers (technology products) like nylon are also polyamides. Hence, the amide is an important element in chemistry and biology, and consequently, its synthesis has remained a focused research area. Many methods are available for the synthesis of amides. The classical methods involve making amides from carboxylic acids and amines. The energy unfavourable direct reaction between an acid and an amine is turned into a favourable pathway using coupling reagents. Coupling agents like DCC, HOBt, PyBOP, etc., are used. However, these reagents generate lots of waste. There are also other selective methods, including Beckmann rearrangement, Schmidt reaction, Willgerodt-Kindler reaction, Passerini reaction, and so on. There has been a recent flurry of revelations about alternative strategies to synthesize amides, with a focus on green or catalytic approaches. In this review, we have covered several alternate methods that use amines as the precursors. Oxidation and reduction are the backbone of synthetic organic transformations. Several elegant oxidizing agents have been developed for the oxidation of alcohols and olefins with selectivity in mind. However, many of these oxidizing agents have the potential to oxidize amines to amides, but they have not been studied earlier as green chemistry was not in much focus then. With the present focus on sustainability and green chemistry, scientists have embarked on synthesizing amides in a greener way. One such way to get amides in a cleaner way is to oxidize amines to amides. Hence, in this review, we have endeavoured to compile all such methods used to make amides or have the potential for such transformation. Other than the use of several oxidizing reagents, tandem oxidation amidation and other miscellaneous methods are included in this review. The reactions that give amides as by-products are also included as such reactions are potential methods to synthesize amides. Mechanisms are also included in relevant places. The review is classified as follows: Oxidation of amines using transition metals, transition metal salts, and transition metal oxides; Oxidation of amines using non-metals; Photocatalytic oxidation of amines; Air oxidation of amines; Electrochemical oxidation; Enzymatic conversion; Oxidative coupling of Aldehydes; Oxidative coupling of Alcohols; Oxidative amidation of Methylbenzenes; and Oxidation of aromatic nitrogen heterocycles.

The modification of drug delivery routes can be used as a promising strategy to improve the therapeutic profile of various drug agents. Herein, the synthesis and molecular modeling of a series of 6,7,8,9-tetrahydrobenzo [b] [1,8] naphthyridines derivatives were reported to explore potent and less toxic scaffolds. The tacrine analogs 6-10 were obtained by an efficient strategy using Friedlander's condensation between 2-aminopyridine-3-carbonitriles 1- 5 and cyclohexanone under microwave irradiations without catalysts and solvents. The synthesized compounds were identified through ¹H NMR, ¹³C NMR, IR. Their inhibition activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were focused as probable drug targets for Alzheimer’s disease (AD). The pharmaco-kinetic properties, the risk of probable hepato-toxic metabolites, and the toxicological properties were predicted using computational methods. The prediction of the toxicity risks via the GUSAR software allowed us to resolve the best approach for drug delivery, namely the subcutaneous, intravenous, or oral route., Also, the GUSAR software was used to reveal all possible adverse effects. All these techniques were tested for the L1-6 compounds by choosing tacrine as a template compound. Among these compounds, the optimal compound L1 was the most potent inhibitor and had the best score binding affinity compared to the reference drug (Tacrine) -7.926 and -7.007 kcal/mol for AChE and BuChE, respectively. Moreover, this same compound presented a satisfying pharmaceutical profile. In the present study, subcutaneous delivery is considered a promising administration of reference drug and their derivatives against AD.