Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Diversified Synthetic Pathway of 1, 4-Dihydropyridines: A Class of Pharmacologically Important Molecules

The current review discusses the different synthetic pathways for one of the most important and interesting heterocyclic ring systems, 1,4-dihydropyridine. This cyclic system depicts diverse pharmacological action on several receptors, channels, and enzymes. Dihydropyridine moiety plays an important role in several calcium-channel blockers. Moreover, it has been exploited for the treatment of a variety of cardiovascular diseases due to its potential antihypertensive, anti-angina, vasodilator, and cardiac depressant activities. Furthermore, it also shows antibacterial, anticancer, anti-leishmanial, anticoagulant, anticonvulsant, anti-tubercular, antioxidant, antiulcer, and neuroprotective properties. Several reports have demonstrated dihydropyridine derivatives as a potentiator of cystic fibrosis transmembrane conductance regulator protein, potent antimalarial agent and HIV-1 protease inhibitor. Herein, we have briefly reviewed different novel chemistry and the synthesis of 1,4-dihydropyridine.

Metal-free multicomponent reactions: a benign access to monocyclic six-membered N-heterocycles

The advent of multicomponent reactions in the synthesis of heterocycles and their ever burgeoning applications in drug development, materials chemistry, and catalysis, have attracted a great deal of current scientific interest. In particular, the metal-free multicomponent synthesis of six membered N-heterocycles has undergone intensive research over the last two decades offering an environmentally benevolent means contrary to traditional metal catalysed reactions. To the best of our knowledge, there exists no exclusive review on the metal-free multicomponent synthesis of six membered N-heterocyles, and hence the present report highlights the progress on metal-free multicomponent reactions with their advantages and mechanistic insights to access monocyclic six-membered N-heterocycles including pyridine, pyrimidine, pyrazine, triazine and their hydrogenated derivatives. The literature is covered since 2000, and the contents offer not only striking methods for divergent synthesis of six-membered N-heterocycles but also put forward some new insights into the exploration of metal-free multicomponent chemistry.

One-electron oxidative dehydrogenative annulation and cyclization reactions

This review focuses on the recent advances in one-electron oxidation involved oxidative dehydrogenative annulations and cyclizations for the intermolecular and intramolecular construction of valuable ring structures.

Identifying key intermediates generated in situ from Cu(II) salt-catalyzed C-H functionalization of aromatic amines under illumination

Copper compounds involved in photocatalysis have recently spurred considerable interest for their novel transformations. However, mechanistic investigations are still in infancy. We find a new type of reaction, that is, Cu(II) salt-catalyzed C-H functionalization of aromatic amines triggered by visible light irradiation. An array of mechanistic observations, including high-resolution mass spectrometry, ultraviolet-visible absorption spectrum, electron spin resonance, x-ray absorption near-edge structure, and density functional theory calculation, have identified the key intermediates generated in situ in the transformation. Integration of single-electron transfer, singlet oxygen (¹O₂), and new absorption species, intermediate I and intermediate II formed in situ from Cu(II) salts and substrate amines or imines, respectively, is responsible for the N-H and C-H bond activation of secondary amines to couple with nucleophiles in air, thereby leading to the formation of quinoline, indolo[3,2-c]quinoline, β-amino acid, and 1,4-dihydropyridine derivatives in moderate to good yields under visible light irradiation at room temperature.

Recent progress in mild Csp3–H bond dehydrogenative or (mono-) oxidative functionalization

This review summarizes recent advances in mild and green dehydrogenative and mono-oxidative Csp³–H bond functionalization reactions, considering both new approaches and the re-elaboration of known methodologies.

Acid-promoted rapid solvent-free access to substituted 1,4-dihydropyridines from β-ketothioamides

1,4-Dihydropyridines were synthesized via a tandem reaction of β-ketothioamides with aldehydes and β-enaminonitriles by AcOH as a promoter within 5 min.