Recent Advances in Organic Synthesis of 3-Amino- or 4-Aminocoumarins

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Coumarin is a privileged scaffold that contains the unique 2H-chromen-2-one motif, and its derivatives are widely distributed in nature, especially in plants. In recent years, due to their diverse pharmacological activities and remarkable photochemical properties, they have attracted significant attention from scientists, which has also prompted the research on the synthesis approaches and the availability of substrates for these compounds. This article is a brief description of the methods for the synthesis of various coumarin derivatives via two- or multi-component reactions involving 3-amino or 4-aminocoumarin reported during 2015-2021. This review may help expand the development of various analogues with coumarin as the basic unit.

Employing of Fe3O4/CuO/ZnO@MWCNT MNCs in the solvent-free synthesis of new cyanopyrroloazepine derivatives and investigation of biological activity

In this research, we synthesized the Fe₃O₄/CuO/ZnO@MWCNT magnetic nanocomposites using water extract of Petasites hybridus rhizome, and the high performance of synthesized catalyst was confirmed by using in the solvent-free multicomponent reactions of isatoic anhydride, N-methylimidazole, alkyl bromides, activated acetylenic compounds and 2-aminoacetonitrile at ambient temperature for the production of new cyanopyrroloazepine derivatives in high yields. This catalyst could be used several times in these reactions and have main role in the yield of product. The synthesized cyanopyrroloazepines have NH groups in their structure and for this reason have good antioxidant activity. Also, employing Gram-positive and Gram-negative bacteria in the disk diffusion procedure confirmed some cyanopyrroloazepines antimicrobial effect. The results showed that synthesized cyanopyrroloazepine prevented the bacterial growth. This used process for preparation of new cyanopyrroloazepine has some improvements such as low reaction time, product with high yields, simple separation of catalyst and products.

PANI-Fe3O4@ZnO nanocomposite as magnetically recoverable organometallic nanocatalyst promoted synthesis of new Azo chromene dyes and evaluation of their antioxidant and antimicrobial activities

A new series of azo chromene dyes were synthesized via a facile cyclocondensation reaction of (E)-1,2-diphenyl-1-diazene and 4-aminocoumarin with 1:2 molar ratio catalyzed by the polyaniline-Fe₃O₄@ZnO nanocomposite (PANI-Fe₃O₄@ZnO). The salient features of this protocol lie in simple experimental procedure, moderate reaction conditions, and uses PANI-Fe₃O₄@ZnO nanocomposite as a magnetically separable heterogeneous catalyst. Two well-known methods were employed for assessing the antioxidant abilities of the target compounds, including free radical trapping of 2,2-diphenyl-1-picrylhydrazyl (DPPH), as well as ferric reducing antioxidant power assay. Also, several synthesized compounds were screened for their in vitro antimicrobial activities by employing the disk diffusion test on Gram-negative as well as Gram-positive bacteria.