This review revealed that among all the natural and synthetic flavonoids, the inhibitory findings suggest that the flavonol moiety can serve as an effective and a lead structural scaffold for the further development of novel TIs.

Heterocycles are the key structures in organic chemistry owing to their immense applications in the biological, chemical, and pharmaceutical fields. Heterocyclic compounds perform various noteworthy functions in nature, medication, innovation etc. Most frequently, pure nitrogen heterocycles or various positional combinations of nitrogen, oxygen, and sulfur atoms in five or six-membered rings can be found. Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes is a popular strategy for the management of numerous mental diseases. In this context, cholinesterase inhibitors are utilized to relieve the symptoms of neurological illnesses like dementia and Alzheimer's disease (AD). The present review focuses on various heterocyclic scaffolds and their role in designing and developing new potential AChE and BChE inhibitors to treat AD. Moreover, a detailed structure–activity relationship (SAR) has been established for the future discovery of novel drugs for the treatment of AD. Most of the heterocyclic motifs have been used in the design of new potent cholinesterase inhibitors. In this regard, this review is an endeavor to summarize the biological and chemical studies over the past decade (2010–2022) describing the pursuit of new N, O and S containing heterocycles which can offer a rich supply of promising AChE and BChE inhibitory activities.

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is the most widely used quinone with a high reduction potential, and it commonly mediates hydride transfer reactions and shows three accessible oxidation states: quinone (oxidized), semiquinone (one-electron-reduced), and hydroquinone (two-electron-reduced). DDQ has found broad utility as a stoichiometric oxidant in the functionalization of activated C–H bonds and the dehydrogenation of saturated C–C, C–O, and C–N bonds. The cost and toxicity of DDQ triggered recent efforts to develop methods that employ catalytic quantities of DDQ in combination with alternative stoichiometric oxidants. The aerobic catalytic approach was established for the selective oxidation of non-sterically hindered electron-rich benzyl methyl ethers and benzylic alcohols, and effectively extended to the oxidative deprotection of p-methoxybenzyl ethers to generate the alcohols in high selectivity. A combination of DDQ and protic acid is known to oxidize several aromatic donors to the corresponding cation radicals. The excited-state DDQ converts benzyls, heteroarenes, fluoroarenes, benzene, and olefins into their radical cation forms as well as chloride and other anions into their respective radicals. These reactive intermediates have been employed for the generation of C–C and C–X (N, O, or Cl) bonds in the synthesis of valuable natural products and organic compounds. To the best of our knowledge, however, there is still no review article exclusively describing the applications of DDQ in organic synthesis. Therefore, in the present review, we provide an overview of DDQ-induced organic transformations with their scope, limitations and the proposed reaction mechanisms.

Nanographenes, or extended polycyclic aromatic hydrocarbons, have been attracting increasing attention owing to their widespread applications in organic electronics. However, the atomically precise fabrication of nanographenes has thus far been achieved only through synthetic organic chemistry. Polycyclic aromatic hydrocarbons (PAHs) are popular research subjects due to their high stability, rigid planar structure, and characteristic optical spectra. The recent discovery of graphene, which can be regarded as giant PAH, has further stimulated research interest in this area. Chemists working with nanographene and heterocyclic analogs thereof have chosen it as their preferred tool for the assembly of large and complex architectures. The Scholl reaction has maintained significant relevance in contemporary organic synthesis with many advances in recent years and now ranks among the most useful C–C bond-forming processes for the generation of the π-conjugated frameworks of nanographene or their heterocyclic analogs. A broad range of oxidants and Lewis acids have found use in Scholl-type processes, including Cu(OTf)₂/AlCl₃, FeCl₃, MoCl₅, PIFA/BF₃–Et₂O, and DDQ, in combination with Brønsted or Lewis acids, and the surface-mediated reaction has found especially wide applications in PAH synthesis. Undoubtedly, the utility of the Scholl reaction is supreme in the construction of nanographene and their heterocyclic analogues. The detailed analysis of the progress achieved in this field reveals that many groups have contributed by pushing the boundary of structural possibilities, expanding into surface-assisted cyclodehydrogenation and developing new reagents. In this review, we highlight and discuss the recent modifications in the Scholl reaction for nanographene synthesis using numerous oxidant systems. In addition, the merits or demerits of each oxidative reagent is described herein.

Terpyridine-based metal complexes have emerged as versatile and indispensable building blocks in the realm of modern chemistry, offering a plethora of applications spanning from materials science to catalysis and beyond.