Current Green Chemistry - Volume 9, Issue 3, 2022

Heterocycles are a valuable type of structural motifs which occupy a major space in the area of medicinal, pharmaceutical, and bioactive natural product chemistry as well as synthetic organic chemistry. Most frequently, nitrogen heterocycles represent a highly significant type of compounds that are extensively employed in agrochemistry, materials science, and synthesis of bioactive complex molecules and it also has a profound role in modern drug design. Among N-heterocycles, bioactive N, Nheterocycles play a crucial role in the drug discovery and development process. Benzimidazoles, oxadiazoles, pyrazoles, pyrazolines, pyridazines, pyrimidines, thiadiazoles, triazoles, etc. are important classes of N, N-heterocycles due to their significant physiological and biological activities as well as versatile synthetic utility. For example, compounds containing an oxadiazole core such as phidianidines A and B display cytotoxicity. Zibotentan including 1,3,4-oxadiazole and pyrazine skeletons was accepted for the treatment of prostate cancer by the FDA, and cefozopran (SCE-2787) comprising 1,2,4-thiadiazole core is a powerful commercial antibiotic. So, there is continuing considerable attention to the improvement of efficient, convenient, and eco-friendly synthetic protocols for the formation of pharmaceutically relevant N,N-heterocycles. In this context, visible light-assisted synthesis of bioactive N,N-heterocycles has a great impact on sustainable development as it constitutes a clean, renewable, and abundant energy source, as well as its encouraging application in industry. Hence, this review aims to deal with the understanding of the visible light-promoted synthesis of bioactive N,N-heterocycles and further stimulate the development of more new relevant strategies.

The diverse biological applications of fluorinated heterocycles make them crucial chemical compounds. Several synthetic processes have been developed for their synthesis. Microwave-assisted synthesis has emerged as an important technique for generating fluorinated heterocycles in an ecofriendly and energy-efficient manner. It provides several benefits like less reaction time, high reaction yield, homogeneous heat distribution leading to lower side reaction, and better control of reaction temperature. Recently there has been significant progress in microwave use for heterocycle synthesis. This article discusses the applications of microwave irradiation in the synthesis of oxygen, nitrogen, sulphur, selenium, and phosphorous containing fluorinated heterocycles.

Introduction: A facile, convenient and general method has been developed for the one-pot three-component synthesis of structurally diverse 2-amino pyran annulated heterocycles from the reactions of aromatic aldehydes, malononitrile and various C-H activated acids in the presence of a catalytic amount of glycine as an efficient metal-free organocatalyst in aqueous ethanol under refluxed conditions. Methods: Using this developed protocol, we were able to synthesize a series of structurally diverse 2- amino pyran derivatives viz., 2-amino-4,5-dihydropyrano[3,2-c]chromenes, 2-amino-4,5-dihydropyrano [4,3-b]pyrans, 2-amino-5,6,7,8-tetrahydro-4H-chromenes, 2'-amino-2,5'-dioxo-5'H-spiro[indoline-3,4'-pyrano [3,2-c]chromene]-3'-carbonitrile and 2'-amino-1,3,5'-trioxo-1,3-dihydro-5'H-spiro[indene-2,4'-pyrano[3,2- c]chromene]-3'-carbonitrile in excellent yields. Result: Synthesis of biologically promising pyrans and spiropyrans, high atom economy, excellent yields, use of metal-free catalyst, less toxic solvents, no chromatographic column purifications, multiple carbon-carbon and carbon-heteroatom bond formations are some of the major advantages of this newly developed protocol. Conclusion: In conclusion, we have developed a simple, convenient, and efficient method for the synthesis of a series of structurally diverse 2-amino pyran annulated heterocyclic derivatives.

In recent decades, green synthesis is increasingly being employed for more environmentally friendly processes and constitutes one central theme of research and development in both academic and industrial chemistry. “Green Chemistry” refers to the design of products and processes that imply the reduction or elimination of substances that are harmful to life or the environment. Due to the benefits of green synthesis, such as reduced waste and expense, not just pharmaceutical firms but also other chemical industries have begun to take steps towards it. Green synthesis techniques include using green solvents, catalysts, and other materials. This review article illustrates the utilization of sustainable methods in the synthesis of biologically active compounds via different green methodologies, such as green solvents, green catalyst, green media, etc. We hope that this chapter will provide a quick overview of the different aspects of green chemistry.