Advances in Organic Synthesis

The multicomponent reactions (MCRs) are vital for producing structurally varied molecular objects. Multicomponent reactions (MCRs) contain three or more synthetic stages and are carried out without isolation of any intermediate, thus requiring mild reaction conditions. They are eco-friendly and cost-effective, have a short reaction time, produce higher yields, and require raw materials. The use of microwave irradiation in green organic synthesis sustains some of the aims of “green and sustainable chemistry.” It offers several benefits over the conventional approach in reducing time, reaction rates, selectivity, product yields, etc. Consequently, the preparation of various heterocycles using a one-pot multicomponent method combined with the application of microwave irradiation is one of the best areas amongst synthetic chemistry. The present study illustrates an overview of recent progress on microwaveirradiated, one-pot multicomponent synthesis of heterocycles.

Olefins are molecules containing double bonds and are an active functional class. They have the potential to react easily due to the pi bonds in their structures. Therefore, olefins themselves form a biologically active class. In addition, they are pioneer molecules in obtaining different derivatives over many reaction types in organic chemistry. The presence of double bonds brings along geometric isomers (e.g., cis, trans, E, Z). The biological activities of olefins differ in geometric isomers. Therefore, stereoselectivity is important for the synthesis of olefins. In stereoselective olefin synthesis, the control is in the hands of the synthetic organic chemist. Stereoselectivity can be controlled with a correct and practical method. In this study, i) geometric isomers ii) biological activities and iii) stereoselective synthesis of olefins are focused. 

This chapter presents an outline of chemical reactions performed while utilizing microwave irradiation. The improvement in economic strategies has taken cognizance and acknowledgment of environment-friendly and cost-effective procedures having the most negligible impact on the environment. Compared to other methods, microwave-assisted methods proved to be more favorable substitutes for conventional laboratory heating systems; many chemical reactions have been accomplished, refining prevailing procedures with practical conclusions than the reactions proceeded under the conventional heating system. Reactions executed via catalysis in an aqueous medium enhanced the eco-friendly procedures, and the reactions executed via catalysis in fluid medium enhanced environmental conventions. In this chapter, we will discuss microwave-assisted catalytic approaches, which have been used for the preparation of various heterocyclic compounds, preparation of peptides, urea and coordination polymers having carboxyl group, and various other chemical reactions. The focus of this work is to highlight the recent advances in the field of Microwave-assisted organic reactions like oxidation, reduction, coupling, functionalization, heterocyclic compounds synthesis, multi-component reactions, and nucleophilic substitutions in water.

 Diaminomaleonitrile (DAMN) is a tetramer of hydrogen cyanide that has been used as the source of purine bases such as adenine. In the literature, DAMN seems to be an essential element used to synthesize various N-heterocyclic compounds. Numerous pharmaceutical and industrial applications have been described for DAMNderived compounds. Among these compounds are five and six-membered N-heterocyclic rings, and since their emergence, DAMN has been extensively investigated as an inexpensive and readily available reagent in synthetic and complex chemistry applications, including those that produce dyes and pigments. As a rich nitrogen source, DAMN occupies an important position in synthetic heterocyclic chemistry. Various synthetic methodologies and diverse heterocyclic structures have been produced and approved across a broad array of industrial fields. This chapter covers five and six-membered rings obtained directly from DAMN.

The peptidomimetic-based design and synthesis of HIV-1 protease and other entry inhibitors are generally oriented to block the viral receptor functionalities in the host cells. Most of the drugs classified under HIV-1 protease inhibitors are primarily optimized through substrate-based design strategies. The peptidomimetic drugs present in the market are non-hydrolyzable by the catalytic aspartic acid residues, an indispensable approach still used in designing potential pharmacophores for protease inhibitors. Thus, a variety of amino acid-containing hybrid small molecules are tested against the HIV-1 protease enzyme by incorporating essential fragments required to block protease functionalities. However, the appearance of mutations in HIV polyproteins is a key parameter to be seriously considered while designing peptidomimetics. Hence, comprehensive knowledge regarding HIV peptidomimetic/medicinal chemistry along with optimization strategy and organic synthesis awareness is critical in the current scenario. The present chapter is aimed to provide in-depth literature on medicinally optimized HIV-1 protease inhibitors, TatTAR RNA blockers with their synthesis, and later it is expanded to the peptidomimetics (entry inhibitors) involved in the envelope glycoprotein (gp120/gp41) and capsid inhibitors. Furthermore, the knowledge-based classification of HIV-1 protease inhibitors, anti-dimer agents, Tat-TAR RNA blockers, and entry inhibitors, along with their synthetic procedures, would serve as a single model template for scientific as well as academic research towards the development of anti-HIV peptidomimetics.

Background: Sulfur and nitrogen heterocyclic systems, especially benzothiazine derivatives, play a vital role in the search for newer drugs due to a significant scientific interest owing to their broad range of synthetic values, various routes, and pharmacological properties. It is known that benzothiazines are divided into five units: 1,2-, 2,1-, 1,3-, 3,1-, and 1,4-benzothiazines. Incorporating two moieties (benzo and thiazine) increases the biological activity of both, and thus their values synthesize new heteropolycyclic systems. Considering their diverse roles in the biological area and synthesis chemistry, huge effects have been found in developing novel and efficient methodologies to synthesize various benzothiazine moieties with different substitutions. Methods: The present chapter comprises an inclusive vision of new and straightforward synthetic strategies to afford benzothiazine and related systems. This chapter covers various reactions for synthesizing benzothiazines, such as alkylation, acylation, aroylation, halogenation, elimination, rearrangement, ring enlargement, reduction, and oxidation. Besides, it also includes other reactions, like cyclization, addition, condensation, cyclocondensation, metal/acid-catalyzed, hydrolysis, aminolysis, hydrazinolysis, complexation, and enantio/regioselective. Moreover, many benzothiazines have been evaluated for their therapeutic activity. Result: The synthesis and chemical reactions of benzothiazines derivatives have been reported. The preparation approaches of some compounds have been found to involve many steps, and others one-pot, resulting in good to excellent yields. Also, many synthesized compounds have shown medicinal properties, such as aldose reductase,anti-inflammatory, analgesic, antimicrobial, antibacterial, antifungal, anticancer, antiviral, antioxidant, herbicidal, and anticarcinogenic, anti-tubercular, antianthelmintic, and antitumor probes. Conclusion: The chapter covers various methods to synthesize benzothiazines and their derivatives, thereby displaying their biological activities.