Current Organic Chemistry - Volume 25, Issue 17, 2021

This account reviews some innovative (“non-classical”) synthetic strategies for the formation of CP bonds developed during the last decades. It provides examples of the most important milestones in this field, highlighting the state-of-art of functional phosphoruscontaining molecules. Among these are the direct functionalization of organic substrates through chlorine-free reactions with elemental phosphorus, syntheses based on phosphinidene (RP) transfer, phosphorylating methodology employing multiple bonds containing P(III) compounds, reactions with stable heterocyclic carbenes, and synthetic approaches using phosphaethynolate and bis(trichlorosilyl)phosphide salts.

The development of simple, atom-economical, and sustainable methodologies for the construction of various functional molecules from easily available substrates has been of great interest in synthetic chemistry. N,N-dimethylformamide (DMF) is an inexpensive, abundant solvent and industrial raw material, and it is considered as an effective polar solvent and also as a versatile reagent in synthetic transformations. During the past few decades, many significant and attractive achievements have been made in the fields of DMF as a reactant. The mini-review will mainly summarize recent advance in the applicants of DMF as a multipurpose building block in synthetic reactions.

In nature, flavonoids constitute a relatively diverse family of aromatic molecules such as flavones, flavonols, flavanones, isoflavone, chalcones, and their derivatives. Natural and synthetic flavonoids have reported diverse biological activity including antimycobacterial, antimicrobial, antiproliferative, antiarrhythmic, antiviral, antihypertensive, antioxidant, and anti-inflammatory. Flavonoids have garnered much attention as potential targets for nutraceuticals and pharmaceuticals. The recent development of ‘‘Green Chemistry’’ has enabled us to manipulate biosynthetic pathways to generate a library of synthetic flavonoids and to diminish the hazards for human health and environmental pollution from conventional methods. This paper presents an exhaustive review of the green synthesis of flavonoids. Green chemistry is the need for the day; hence chalcones can be synthesized in an eco-friendly manner without using solvents. The chalcone synthesis involves the solvent-free solid-state trituration between acetophenone derivatives and substituted benzaldehydes in the presence of NaOH/KOH as a base (Claisen-Schmidt reaction). Using these chalcone derivatives, synthesis of flavonoids can be done. In the pharmaceutical arena, economical bulk production of different types of flavonoids has been successfully established by green chemistry techniques.

Thiophene derivatives, either “small molecules,” oligomers, or polymers, play a role of primary importance among organic semiconductors, therefore, they have numerous and different technological applications in the field of Organic Electronics. For this reason, thiophene-based materials are found in devices, such as Organic Light-Emitting Diodes (OLEDs), Organic Field-Effect Transistors (OFETs), organic solar cells (OSCs), organic photodetectors, etc. Oligothiophenes and polythiophenes have common excellent charge transport properties and synthetic procedures that are now well established. Furthermore, oligothiophenes do not possess the intrinsic disadvantages of polythiophenes, such as the lack of welldefined structures and the inevitable presence of impurities. Electrochemistry can give a significant contribution to the field of oligothiophenes not only by allowing the determination of the Highest-Occupied Molecular Orbital (HOMO) and the Lowest-Unoccupied Molecular Orbital (LUMO) energy levels by the means of Cyclic Voltammetry (CV), but also through rendering oligothiophenes syntheses more expeditiously in comparison with the classical organic ones. This review outlines the application of electrochemistry techniques in the synthesis of oligothiophene derivatives.

The study aimed at a novel catalytic eco-friendly one-pot reaction for the synthesis of some new thiosemicarbazone and N-thiocarbamoyl pyrazole derivatives. The prepared and characterized silica-supported zinc chloride (ZnCl2/SiO2) catalyst has been presented for promoting the one-pot reaction between isothiocyanates (1 mmol), hydrazine (1.2 mmol) and 1,3- dicarbonyl (1 mmol) compounds under solvent-free conditions. The identification data explained that the thiosemicarbazones products were obtained in the case of using ethyl acetoacetate as an example of 1,3-dicarbonyl compounds and N-thiocarbamoyl pyrazole derivatives products were obtained in the case of using acetylacetone as an example of 1,3- dicarbonyl compounds. The presented catalyst silica-zinc chloride has been considered an eco-friendly and recyclable catalyst compared to the other reported catalyst. The biological activity of the synthesized compounds targeting the bacterial cell wall was predicted by the molecular docking as an undecaprenyl pyrophosphate synthase (UppS) inhibitor. Antioxidant data revealed the compounds 2a, 3d, 3e, 3f, 3g, 3h, and 3j to be promising antioxidant agents compared to ascorbic acid as a reference molecule.