Current Organic Chemistry - Volume 25, Issue 12, 2021

Carbon-carbon bond formation is the essence of organic synthesis, and for that, many strategies have been developed to accomplish this goal. Several of these strategies are conducted to form diverse structures bearing the α,α-diarylcarbonyl motif, in the form of 1,2,2-triarylethanones, which are unities present in a number of natural products and biologically active compounds. These privileged carbonyl compounds have been used as building blocks or intermediates for the synthesis of dibenzo[a,c]phenanthridines, analogues of biologically active benzo[c]phenanthridine alkaloids, as well as useful synthons for Droloxifene and remarkably for Tamoxifen, the most widely used drug for the treatment of breast cancer. Focusing on the literature progress from 2000 to 2020 and considering the synthetic and biological value of the aforementioned carbonyl compounds, the present review explores the diverse metal-free, metal-mediated, C–H bond activation, α-monoarylation, α,α-diarylation, umpolung processes, Nheterocyclic carbene (NHC), and deoxygenation, among other synthetic approaches directed to the synthesis of 1,2,2-triarylethanone derivatives. Moreover, several of their mechanistic proposals are also briefly discussed in this review. In view that most of these strategies are accompanied by carbon-carbon bonds formation through ketonebased α-arylation processes, the reported data are organized into concise Tables/Schemes to facilitate comparison, and to underscore the key points of this review.

Background: N,N'-Diacylhydrazines are involved in many synthetic transformations. The current work reviews the synthesis of N,N'-diacylhydrazines and their use in various synthetic transformations. Results: Three synthetic routes are commonly used to produce N,N'-diacylhydrazines. They are produced through the coupling of acyl chlorides and carbohydrazides, the reaction of hydrazine hydrate and carboxylic acids or isocyanates, and the dimerization of carbohydrazides. They can be oxidized to produce the corresponding esters and act as precursors in the synthesis of various heterocycles such as 1,3,4-oxadiazoles, 1,3,4-thiadiazoles, 1,2,4-triazoles, pyrazoles, tetrazines, and crown ethers. Conclusions: Various synthetic procedures have been reported for the production of N,N'- diacylhydrazines. N,N'-Diacylhydrazines are involved in the synthesis of various heterocycles.

Natural compounds are the prominent sources for the synthesis of abundant biologically active substances in medicinal chemistry. Camphor exists in two enantiomeric forms i.e., R and S, or both, which are readily obtainable. Camphor is a small molecule with chirality property that binds to some active site, together with its low cost and convenience to transform into synthetically useful derivatives and one of the most important monoterpenoids widely spread in plants and has been used as starting material for the various camphor based derivatives which exhibit several biological activities include antimicrobial, antiviral, antioxidant, analgesic and anti-cancer. Many of those simple derivatives are commercially available in the form of camphor sulfonic acid or ketopinic acid that can be easily be produced from camphor. This compound is primarily used as a chiral starting material in the enantiospecific synthesis of natural products is because of its available methods for the direct or indirect introduction of functionality at C-3, C-5, C-8, C-9, and C-10 carbon atoms. In this study, heterocyclic compounds derived from camphor are arranged in different groups as Camphor-Derived Simple Heterocycles, Fused Camphor-Derived Heterocycles, Spiro Camphor-Derived Heterocycles, Ring Expanded Camphor-Derived Heterocycles and Camphor derived metal complexes. This study summarizes the transformations of camphor and its derivatives along with their biological activities.

The investigation of effective and green synthetic routes to approach to novel fused heterocycles with pyridopyrimidine and pyridopyrazine scaffolds stirs up broad interest from scientists as they are capable of providing valuable properties such as anticancer and antimicrobial activities and they are proved γ-secretase modulators, polymers, and corrosion inhibitors. This causes a steady increase in the number of publications on titled condensed systems. The present review article summarizes recent literature data from 2010 to 2020 on the methods of synthesis, chemical transformations and biological properties of condensed bicyclic systems of pyridopyrimidine and pyridopyrazine with a bridgehead nitrogen atom to establish the current state of the art in this area.

Background: Synthesis of a series of 2-(dichloromethyl)pyrazolo[1,5- a][1,3,5]triazines was carried out and evaluated in vitro for their anticancer activity against a panel of 60 cell lines derived from nine cancer types. Methods: The joint quantum-chemical and experimental study of the influence of the extended πconjugated phenyl substituents on the electron structure of the pyrazolo[1,5- a][1,3,5]triazines as Pharmacophores were performed. It is shown that the decrease in the barriers to the rotation of phenyl substituents in compounds 1-7 possibly leads to an increase in the anti-cancer activity, which is in agreement with the change in the parameter biological affinity Φ0. Analysis of the S0 → S1 electronic transitions (π→π*) of the pyrazolo[1,5- a][1,3,5]triazines shows that an increase in their intensity correlates with anti-cancer activity. Results: Thus, the introduction of phenyl substituents increases the likelihood of investigated pyrazolo[1,5-a][1,3,5]triazines interacting with protein molecules (Biomolecule) by the π-stacking mechanism. In both methyl and phenyl derivatives of pyrazolo[1,5-a][1,3,5]triazines, the second electronic transition includes the n- MO (the level of the lone electron pair in two-coordinated nitrogen atoms). The highest intensity of the η→π* electronic transition is observed in pyrazolo[1,5-a][1,3,5]triazine with pyridine residue, which does not exhibit anticancer activity, but exhibits antiviral activity [13]. Conclusion: It can be assumed that the possibility of the formation of [Pharmacophore-Biomolecule] complex by hydrogen bonding ([H-B]) mechanism with protein molecules increases.