Current Organic Chemistry - Volume 26, Issue 17, 2022

Aminocoumarins are found to be present in many natural products, pharmaceuticals, and organic materials. These derivatives demonstrate numerous biological activities including DNA gyrase, anti-proliferative and anti-breast cancer activities. Among the allaminocoumarin derivatives, 4-aminocoumarin derivatives have been reported to exhibit anticancer and anti-fungal properties. 4-Aminocoumarins and their derivatives are important precursors for the synthesis of coumarin fused N-heterocycles. Due to the presence of an amino group as well as enamine carbon, it is very reactive towards electrophiles and in most of the cases, it has a higher tendency to cyclize immediately by the various reaction path ways and provides the heterocyclic products. Unlike other aromatic amines, it did not give any Schiff base on reaction with aldehydes or ketones. Lamellarins, ningalin A, ningalin B, schumanniophytin, santiagonamine, goniothaline, and polyneomarline C are important natural coumarin fused N-heterocycles and show excellent biological activities, including antitumor, reversal of multidrug resistance, anti-HIV, wound healing, anti-malarial, anti-hepatitis, and anti-syphilis activities. The synthesized coumarin fused N-heterocycles have been reported to display Topoisomerases I inhibitory, DYRK1A inhibitory, and anti-cancer activities. Most of the syntheses of pyrrolo/imidazolo/indolo[3,2-c]coumarin, pyrido/quinolino[3,2-c]coumarins, pyrimidino[ c]coumarin and oxazino[c]coumarin have been synthesized easily from 4-aminocoumarin. This paper reviews the research data in the literature on the synthesis of bioactive coumarin fused heterocycles using 4-aminocoumarin derivatives over the period of 2-3 decades. It covers the synthetic applicability of 4-aminocoumarin for the development of coumarin fused 5-, 6-, and 8-membered ring derivatives via classical reaction protocols, microwavemediated reactions, organo-catalyzed reactions, transition metal-catalyzed reactions, and green reaction protocols.

Ruthenium-catalyzed amination reactions have gained much attention in recent times. Due to the low cost and versatile nature of ruthenium, its chemistry is expanding rapidly. The amination reaction provides an efficient pathway to synthesize organonitrogen compounds. These reactions are highly regio- and stereoselective and exhibit wide substrate scope. This review gives an overview of the ruthenium-catalyzed allylic amination reactions covering literature up to 2021.

Amino heterocycles are important in drug design due to their unique intrinsic and physicochemical properties. Though these molecules look simple, their selective reduction is challenging because of their rich electron density in the ring. Additionally, reducing nitro groups in heterocycles is crucial in designing different materials. With this in view, several reduction methods have been developed and applied to various heterocyclic compounds. However, there is no dedicated report on these special types of compounds. With careful analysis, the studies are systematically summarized from conventional methods to advance materials based on their catalytic activity, durability, recyclability, and stability. Further, detailed insights are discussed to motivate chemists working in catalysts.

Green solvent is a topic of increasing attention in modern chemistry because of the consciousness of the effect of solvents on air quality, energy usage, pollution, and continuous climate change. Over the past few years, remarkable progress has been made to accomplish these goals by giving interest in sustainable synthesis. For sustainable development, continuous efforts have been put forward for addressing these issues and the chemical approaches are now analysed for the usage of solvents. Realizing solvent property is a crucial area of green chemistry, and therefore the solvents were categorized by their handling techniques, ecological, and healthiness (ESH) features. The focus of this ranking is to help the researchers in choosing their reaction solvent efficiently, keeping in mind the ESH values of the solvents and discouraging them from using environmentally harmful and toxic solvents which are commonly used in laboratories. In this review article, we are trying to consider various synthetic methodologies of the most protuberant sustainable solvents such as polyethylene glycol, supercritical CO2, and water. We herein examine not only the chemical reactions but also represent the mechanism and synthetic utility of each class of solvent inside the background of the reactions for which it is used, but also documented the widespread substrate scope of the reaction. A broad range of economic and environmental factors are also demonstrated, giving a wider display of the current status of sustainable solvent research and development.

Continuous flow chemistry refers to the delicate chemical production processes, without interruptions and with the best possible use. It is a practice identified as an opportune for the incorporation of the principles of Green Chemistry into economically favorable industrial processes. The purpose of this work is to verify the efficiency advantage and lower the wastage of time and materials that continuous flow extraction can bring to industries, compared to the conventional methods, such as the batch method, for bioactive compound extraction. Herein, a systematic literature review of the available research was made, and the data were collected from articles in different languages (in Portuguese, Spanish, and English), dissertations, and theses, including the Web of Science database. By collecting, analyzing, and comparing publications in which tests using different methodologies for extracting compounds were conducted, we obtained results with the acquisition of extensive information about reactors and machinery that make extraction through continuous flow chemistry viable on a laboratory scale. We observed the expansion of the exothermic synthetic step options that are not possible in batch reactors. Continuous flow chemistry proves to be very advantageous compared to other conventional methods owing to several factors, such as environmental and economical, especially because it facilitates the reuse of waste materials in industrial processes. It not only allows a relatively fast and efficient extraction but also proves to be less aggressive to the environment.