A new cross-conjugated mesomeric betaine

A Review on Chemistry and Methods of Synthesis of 1,2,4-Triazole Derivatives

This review provides a comprehensive overview of research on 1,2,4-triazoles conducted over the last fifteen years. 1,2,4-Triazoles are highly significant in the pharmaceutical industry, with numerous compounds from this class used clinically as antifungal, antiviral, antibacterial, anti-inflammatory, and antitubercular agents. Beyond their pharmaceutical relevance, this review also explores their role in material science and agriculture. In material science, 1,2,4-triazoles are gaining prominence, particularly in the development of energetic materials (EMs), due to their exceptional properties such as thermal stability, coordination ability, and performance comparable to well-known explosives. Their applications extend to polymers, corrosion inhibitors, and metal-organic frameworks (MOFs), and they play a significant role in the development of functional materials for sensors, catalysis, and energy storage. Additionally, the review addresses general aspects and synthetic methodologies for the functionalization and construction of the 1,2,4-triazole ring. Synthetic methods discussed include metalation synthesis, cyclization of hydrazine derivatives, multicomponent reactions, cyclization of amides and amidines, and microwave-assisted synthesis. Given the significance of the triazole scaffold, its synthesis has garnered considerable attention due to its wide-ranging applications across various industrial sectors.

3-Thioxo-3H-indolizinium-1-olates and Related Pseudo-Cross-Conjugated Heterocyclic Mesomeric Betaines: Synthesis and Spectral Features

The first example of the synthesis of 3-thioxo-3H-indolizinium-1-olates, which further expands a limited class of pseudocross-conjugated heterocyclic mesomeric betaines isoconjugate to odd nonalternant hydrocarbon anion, is reported. These unique, moderately colored heterocyclic products result from a developed three-component reaction of cyclopropenones, pyridines, and sulfur. The protocol is distinguished by simple and mild reaction conditions that avoid expensive reagents or exotic catalysts, exhibiting high functional group tolerance. The broad scope of the reaction is particularly remarkable in light of the dramatic influence of pyridines' substituents on the reactivity of corresponding indolizin-1-ols, the key intermediates that proved to be highly thiophilic. In addition, an oxidative coupling of indolizin-1-ol in situ with p-tropoquinone oxime acetate is discovered. The reaction involves the C3 and C5 positions of the indolizin-1-ol and results in unusual indolizine-aminotropolone combinations. For the 3H-indolizinium-1-olate type of PCC HMBs, some general considerations concerning light absorption and NMR regularities were formulated.

Organic Donor-Acceptor Complexes As Potential Semiconducting Materials

In this review article, the synthesis, characterization and physico-chemical properties of the organic donor-acceptor complexes are highlighted and a special emphasis has been placed on developing them as semiconducting materials. The electron-rich molecules, i. e., donors have been broadly grouped in three categories, namely polycyclic aromatic hydrocarbons, nitrogen heterocycles and sulphur containing aromatic donors. The reactions of these classes of the donors with the acceptors, namely tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), tetracyanobenzene (TCNB), benzoquinone, pyromellitic dianhydride and pyromellitic diimides, fullerenes, phenazine, benzothiadiazole, naphthalimide, DMAD, maleic anhydride, viologens and naphthalene diimide are described. The potential applications of the resulting DA complexes for physico-electronic purposes are also included. The theoretical investigation of many of these products with a view to rationalise their observed physico-chemical properties is also discussed.

Unique Pseudo-Cross-Conjugated Mesomeric Betaines via an Iodate-Promoted Reaction of 3,3-Difluorocyclopropenes, Pyridines, and Anilines

A simple method for the synthesis of (E)-3-arylimino-3H-indolizin-4-ium-1-olates by an iodate-promoted multicomponent reaction between 3,3-difluorocyclopropenes, pyridines, and anilines was discovered. The reaction products belong to a limited and underexplored class of pseudo-cross-conjugated heterocyclic mesomeric betaines isoconjugated with odd nonalternant hydrocarbon anions, whose properties were studied. Reversible nucleophilic addition at the C5 position was revealed as their main chemical feature, which had an access to novel fully conjugated 1,5-dioxo-3-arylamino-1,5-dihydroindolizine and tetracyclic 4-oxo-4,6-dihydrocyclopenta[4,5]pyrimido[2,1,6-cd]indolizine ring systems in one step. Both the synthesis of betaines and their transformations demonstrate a high level of functional group compatibility, allowing the ready preparation of a number of structurally attractive compounds for materials or medicinal chemistry.