TMSCl-catalysed condensation of α-diketone compounds with urea/thiourea derivatives under solvent-free conditions

Investigation on the Synthesis, Application and Structural Features of Heteroaryl 1,2-Diketones

A set of unsymmetrical heteroaryl 1,2-diketones were synthesized by a heteroarylation/oxidation sequence with up to 65% isolated yields. Palladium catalyst XPhos Pd G4 and SeO₂ were the key reagents used in this methodology, and microwave irradiation was utilized to facilitate an efficient and ecofriendly process. The application of heteroaryl 1,2-diketones is demonstrated through the synthesis of an unsymmetrical 2-phenyl-3-(pyridin-3-yl)quinoxaline (5a) from 1-phenyl-2-(pyridin-3-yl)ethane-1,2-dione (4a). The lowest energy conformations of 4a and 5a were located using Density Functional Theory (DFT) at the M06-2X/def2-TZVP level of theory. Two lowest energy conformations of 4a differ with respect to the position of the N atom in the pyridyl ring and 0.27 kcal/mol energy difference between them corresponds to 60.4 and 39.6% at 50 °C in toluene. Four lowest energy conformations for 5a have the energy differences of 0.01, 0.03 and 0.07 kcal/mol that corresponds to 26.0, 25.7, 24.9 and 23.4%, respectively. A comparison of 4a and 5a to the less hindered analogs (oxalyl chloride and oxalic acid) is used to investigate the structural features and bonding using Natural Bond Orbital (NBO) analysis.

Synthesis, Characterization, and Antibacterial Activities of 1H-Imidazo [5, 6-f] [1,10] Phenanthroline-2(3H)-Thione and Its Ni(II) and Cu(II) Complexes

As multidrug resistant pathogens are emerging, the search for novel potent drug candidates is ever going. Heterocycles are known by their broad spectrum of biological activities, so a search for a new drug from heterocycles can elevate the chance of success. The aim of this study was to obtain novel potent antimicrobial compounds. In line with this, 1H-imidazo [5, 6-f] [1,10] phenanthroline-2(3H)-thione and its complexes (Ni(II) and Cu(II)) were synthesized, characterized, and evaluated against bacterial strains. The compounds were characterized by elemental analyses (C, H, N, and S), FT-IR, 1H-NMR, 13C-NMR, AAS, UV-Vis spectra, and molar conductivity measurement. The results showed that the ligand is bidentate, and the molar conductivity measurement indicates that complexes are electrolytic. Electronic spectral study showed octahedral and distorted octahedral geometry for the Ni(II) and Cu(II) complex, respectively. The ligand and its complexes were screened against four bacterial strains using disk diffusion method. The result revealed that the Ni(II) complex showed more bioactivity than gentamicin against Staphylococcus aureus and Escherichia coli, while the Cu(II) complex is more active than the Ni(II) complex against Bacillus subtilis. Both Cu(II) and Ni(II) complexes exhibit higher antibacterial activities than the free ligand.

Synthesis of glycolurils and their analogues

Glycolurils — tetrahydroimidazo[4,5-d]imidazole-2,5(1H,3H)-diones — have found widespread applications in various fields of science and technology. Among them, there are pharmacologically active compounds (antibacterial, nootropic, neurotropic agents, etc.), explosives, gelators, etc. They are used as building blocks in supramolecular chemistry. Therefore, the development of new methods for the synthesis of glycolurils and their analogues has constantly attracted the attention of researchers. In this review, we analyze various approaches to the synthesis of glycolurils and their analogues. The review covers both classical reactions of ureas and related compounds with α-dicarbonyl compounds or with 4,5-dihydroxyimida-zolidin-2-ones (-thiones) and their imino analogues and new original reactions of 4,5-dihydroxyimidazolidin-2-ones (-thiones), imidazolinones and their bicyclic analogues with ureas and KNCS in the presence of acids, condensations of 1,4-disubstituted 1,4-diaza-1,3-dienes with isocyanic and/or isothiocyanic acids or isocyanates, triazine ring contraction in imidazotriazines to give the imidazolidine ring, and transformations of urazoles.

The bibliography includes 129 references.