Benzimidazole structure contains imidazole ring fused with phenyl ring at 4-and 5-position. The mono and disubstituted derivatives of benzimidazole are very interesting heterocyclic organic molecules, synthesized by a simple nucleophilic substitution reaction and condensation method between ophenylenediamine with carbonyl compound under different conditions are reported, and as time passed away, the method also be reported in favor of the environment-friendly with good yield product. We cover the literature up to the end of 2019 in which very recently reported synthetic route to access benzimidazole scaffolds are discussed. We are focus on the evaluation of synthetic route to construct monosubstituted-benzimidazole (MSBs) and disubstituted-benzimidazoles (DSBs), via various methods involving condensation, cyclization or employing green chemistry aspect such as utilizing solventfree conditions, metal-free conditions, or using nanoparticle catalyst etc. Benzimidazoles found in the natural system display a wide range of pharmaceutical properties have been reported. The scaffolds are characterized as structurally potential ligands which can bind to different receptor sites for the discovery of various immerging drugs. Therefore, benzimidazole is recognized as a potent scaffold in the pharmaceutical industry and diverse synthetic pathways have been developed to prepare its functionalized derivatives which are described in this review.

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: Quinazoline is an organic heterocyclic molecule in which two six-membered aromatic rings are fused. Two nitrogen are present in the quinazoline molecule at 1 and 3 positions that’s why it is also known as 1,3-diazanaphthalene. Presence of these two nitrogen atoms in 1,3-diazanaphthalene increases the usefulness of this molecule in the field of pharmaceutical sciences. Many reactions have been reported to prepare 1,3-diazanaphthalene by aminobenzonitrile, o-aminobenzohydrazide, aminobenzamide, aminoacetophenone and aminobenzoketone under different solvent condition but condensation of anthranilic acid with aromatic aldehyde is the most common method. Later metal-free and solvent-free condition dominated over the old methods. This review describes synthesis of 1,3-diazanaphthalene under different metal catalyst, reagents, solvent-free condition and under microwave radiation through nucleophilic substitution reaction, condensation, and aromatization. In biological sciences, 1,3-diazanaphthalene derivatives have got important place due to its ability to bind different target sites and subsequently discovery of many drug structures.

: The current emergency in China causes by the spreading 2019-nCoV is to create a very critical condition in human society known as COVID-19. This virus is very complex, transfer human-to-human, belonging to the family coronaviridea and genera betacoronavirus. By the infection, common symptoms have been observed like a sudden high fever in between 1 to 9 days and some of the problem in the neck region with starting infection day and then this infection spread into the lungs causes novel coronavirus pneumonia (NCP) and kidney failure. At this time, to find a solution to the problem, a lot of researchers is working together to solve this problem. According to the WHO, more than 3588773 cases were confirmed around globally by the infected COVID-19. Many of the receptor protein of the SARS-CoV-2 and target proteins of the human cell is responsible for endocytosis like Mpro or 3CLpro, RNA polymerase, spike protein etc. These proteins play a vital role in the life cycle of SARS-CoV-2. As anti-COVID-19 drugs, many compounds were designed by computational methods to inactive of the receptor protein has been reported. Some of the drugs are ongoing under trail, and these drugs will be shows strong potent activity against this virus in the future. In this study represent about the synthetic and computational designed approach drugs and compounds for the inhibit receptor of SARS-CoV-2. This review will be helpful to find a new approach drug as an inhibitory receptor of SARS-CoV-2 structure and their life cycle, and also be helpful to identify and synthesis of effective drug and vaccine candidates for anti-novel coronavirus. We will be able to fight this coronavirus with our new time in this world.

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