Current Organic Chemistry - Volume 26, Issue 3, 2022

This unprecedented review with 322 references provides a critical up-to-date picture of the Pd-catalysed intermolecular direct C–H bond arylation of heteroarenes with arylating reagents alternative to aryl halides that include aryl sulfonates (aryl triflates, tosylates, mesylates, and imidazole- 1-sulfonates), diaryliodonium salts, [(diacetoxy)iodo]arenes, arenediazonium salts, 1-aryltriazenes, arylhydrazines and N’-arylhydrazides, arenesulfonyl chlorides, sodium arenesulfinates, arenesulfinic acids, and arenesulfonohydrazides. Particular attention has been paid to summarise the preparation of the various arylating reagents and to highlight the practicality, versatility, and limitations of the various developed arylation protocols, also comparing their results with those achieved in analogous Pd-catalysed arylation reactions involving the use of aryl halides as electrophiles. Mechanistic proposals have also been briefly summarised and discussed. However, data concerning Pd-catalysed direct C–H bond arylations involving the C–H bonds of aryl substituents of the examined heteroarene derivatives have not been taken into account.

The use of 1H-1,2,3-triazoles has become an important scaffold for applications in different technological sectors. Therefore, we sought to carry out technological monitoring to understand the international scenario involving 1H-1,2,3-triazoles from the patents filed, in addition to evaluating the relationship between the growth in the number of patents and the improvement of strategies for obtaining these compounds via a metal-catalyzed azide-alkyne cycloaddition reaction. Technological monitoring was performed with the support of the PatentInspiration ® platform, using the keywords "1,2,3-triazol", "1,2,3-triazole", and "1,2,3- triazolyl". A total of 960 registered patents were found, most for the years 2014 and 2019. The main filers were prestigious multinational companies, such as Syngenta, Merck, Sandoz, Pfizer, and Bayer. The United States, China, Japan, and Germany lead patent registrations, mainly addressing innovations in chemistry and metallurgy, human needs, and new technologies. These results help to understand the state of innovation for this topic, pointing out the characteristics of the main discoveries concerning 1H-1,2,3-triazole derivatives.

Propellanes and derivatives have attractive properties due to their unique structure. Therefore, [3.3.3] propellanes, containing tricyclic structures with one of the carbon-carbon bonds common in three rings, were used in natural products, pharmaceutical compounds, and heterocyclic compounds, which were biologically important. The various multi-component reactions were applied in the synthesis of propellanes, which are highlighted throughout this review.

With the increasing analysis of saving the environment, the researchers demonstrated much effort to replace toxic chemicals with environmentally benign ones. Eutectic mixtures are those solvents that fulfill the criteria of green solvents. The synthesis of organic compounds in the chemical and pharmaceutical industries makes it necessary to find unconventional solvents that cause no harmful impact on health parameters. This review showed that using deep eutectic mixture-based solvents to overcome the hazardous effects of harmful volatile organic solvents over the past few years has gained much more appeal. In most applications, deep eutectic mixtures are used for a solvent or co-solvent role, as they are easy to use, easy dissolution of reactants, and non-evaporative nature. However, deep eutectic mixtures have also been investigated as catalysts, and this dual functionality has much scope in the future, as a significantly less range of deep eutectic mixtures is utilized for this.

Owing to useful physio-chemical properties of furo-coumarin derivatives, their synthetic and mechanistic investigation has been reported here. We have demonstrated a range of synthetic approaches to access furan-fused coumarin derivatives. Many metalmediated, base, and acid-catalyzed approaches have been revealed for the formation of this coumarin-based fused heterocycles of biological importance. In addition to this, microwaveassisted synthetic routes have also been revealed. The last and most useful approach for the synthesis of these heterocycles includes the use of purely solvent as a reaction media for synthesizing these interesting classes of heterocycles.