Impact of the central atom and halido ligand on the structure, antiproliferative activity and selectivity of half-sandwich Ru(II) and Ir(III) complexes with a 1,3,4-thiadiazole-based ligand

Half-sandwich complexes [Ru(η6-pcym)(L1)X]PF6 (1, 3) and [Ir(η5-Cp*)(L1)X]PF6 (2, 4) featuring a thiadiazole-based ligand L1 (2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-thiadiazole) were synthesized and characterized by varied analytical methods, including single-crystal X-ray diffraction (X = Cl or I, pcym = p-cymene, Cp* = pentamethylcyclopentadienyl). The structures of the molecules were analysed and interpreted using computational methods such as Density Functional Theory (DFT) and Quantum Theory of Atoms in Molecules (QT-AIM). A 1H NMR spectroscopy study showed that complexes 1-3 exhibited hydrolytic stability while 4 underwent partial iodido/chlorido ligand exchange in phosphate-buffered saline. Moreover, 1-4 demonstrated the ability to oxidize NADH (reduced nicotinamide adenine dinucleotide) to NAD+ with Ir(III) complexes 2 and 4 displaying higher catalytic activity compared to their Ru(II) analogues. None of the complexes interacted with reduced glutathione (GSH). Additionally, 1-4 exhibited greater lipophilicity than cisplatin. In vitro biological analyses were performed in healthy cell lines (CCD-18Co colon and CCD-1072Sk foreskin fibroblasts) as well as in cisplatin-sensitive (A2780) and -resistant (A2780cis) ovarian cancer cell lines. The results indicated that Ir(III) complexes 2 and 4 had no effect on human fibroblasts, demonstrating their selectivity. In contrast, complexes 1 and 4 exhibited moderate inhibitory effects on the metabolic and proliferation activities of the cancer cells tested (selectivity index SI > 3.4 for 4 and 2.6 for cisplatin; SI = IC50(A2780)/IC50(CCD-18Co)), including the cisplatin-resistant cancer cell line. Based on these findings, it is possible to emphasize that mainly complex 4 could represent a further step in the development of selective and highly effective anticancer agents, particularly against resistant tumour types.

Agar-entrapped sulfonated DABCO: Agelly acidic catalyst for the acceleration of one-pot synthesis of 1,2,4-triazoloquinazolinone and some pyrimidine derivatives

In this project, a recently synthesized DABCO-based catalyst is entrapped in agar to reduce its moisture sensitivity leading to enhancement of its stability and catalytic activity. After preparation and identification this new reagent is used as an efficient and environmentally safe catalyst for the preparation of 1, 2, 4-triazoloquinazolinone and some pyrimidine derivatives. This method is accompanied with some superiorities such as, simple operation, mild and green conditions, use of low cost and non-hazardous natural material, short reaction times, easy preparation methods and simple work-up procedures. The prepared catalyst can be re-used for several times in all of the studied reactions without any appreciable loss in its activity.

Two decades of the synthesis of mono- and bis-aminomercapto[1,2,4]triazoles

4-Amino-5-mercapto[1,2,4]triazole and its 3-substituted derivatives have proven to be of biological interest and provide access to a new class of biologically active heterocyclic compounds for biomedical applications. This study will be helpful for scientific researchers interested in the chemistry of bifunctional versatile compounds as it provides a collection of all the methods for the preparation of 3-substituted-4-amino-5-mercapto[1,2,4]triazoles with aliphatic, aromatic, and heterocyclic moieties during the period from 2000 to mid-2020.

4-Amino-5-mercapto[1,2,4]triazole and its 3-substituted derivatives have proven to be of biological interest and provide access to a new class of biologically active heterocyclic compounds for biomedical applications.

Reaction of N-imidoylthioureas with Dimethyl Acetylenedicarboxylate: Synthesis of new 1,3,5-thiadiazepines

The reaction of N-imidoylthioureas 2a–e with dimethyl acetylenedicarboxylate (DMAD, 1) led unexpectedly to the 1,3,5-thiadiazepines 6a–e. The mechanism of the reaction is discussed.

Synthesis and antimicrobial activity of new piperazine-based heterocyclic compounds

The hydrazide

Microwave-assisted and conventional synthesis of novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton

Carbothioamides

tert-Butyl 2-{[5-(4-cyano-phen-yl)pyridin-3-yl]sulfon-yl}acetate

In the title compound, C₁₈H₁₈N₂O₄S, the dihedral angle between the aromatic rings is 33.71 (9)° and an intra­molecular C—H⋯O hydrogen bond closes an S(6) ring. In the crystal, mol­ecules are linked by C—H⋯O and C—H⋯N hydrogen bonds to generate a three-dimensional network. A very weak aromatic π–π stacking inter­ction is also observed [centroid–centroid separation = 3.9524 (10) Å].

6-(4-Fluoro-phen-yl)-3-phenyl-7H-1,2,4-tri-azolo[3,4-b][1,3,4]thia-diazine

In the title compound, C16H11FN4S, the dihedral angles between the triazole ring and the phenyl and fluoro-benzene rings are 23.22 (17) and 18.06 (17)°, respectively. The six-membered heterocyclic ring adopts a distorted envelope conformation, with the methyl-ene C atom as the flap. In the crystal, the mol-ecules are linked by two C-H⋯N and C-H⋯F inter-actions along [010], forming C(5), C(8) and C(13) chains repectively. C-H⋯π inter-actions involving the phenyl ring and π-π inter-actions [centroid-centroid separation for triazole rings = 3.5660 (18) Å] are also observed.

Microwave assisted synthesis of some hybrid molecules derived from norfloxacin and investigation of their biological activities

Norfloxacin was converted to 7-(4-amino-2-fluorophenyl)piperazin derivative (2) via the formation of nitro compound. The synthesis of the norfloxacin derivatives containing 1,3-thiazole or 1,3-thiazolidin moiety was performed from the reaction of 4-chlorophenacylbromide or ethyl bromoacetate with compounds 4-7 obtained starting from 2. 3-Fluoro-4-[4-(2-methoxyphenyl)piperazin-1-yl]aniline (14), 5-{[4-(2-methoxyphenyl)piperazin-1-yl]methyl}-4-phenyl-4H-1,2,4-triazole-3-thiol (18) and {[4-(2-methoxy phenyl)piperazin-1-yl]methyl}-1,3,4-oxadiazol-2-thiol (19) were obtained starting from 1-(2-methoxyphenyl)piperazine by several steps. The treatment of hydrazide (16) with several aldehydes afforded N'-[(2-hydroxyphenyl)methylen]- (20), N'-[(3-hydroxy-4-methoxy phenyl)methylen]- (21) or N'-[1H-indol-3-ylmethylene]-2-[4-(2-methoxyphenyl)piperazin-1-yl]acetohydrazide (22). Then, compounds 14, 18, 19 and 22 were condensed with 7-[4-(chloroacetyl)piperazin-1-yl]-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (3) that was obtained from norfloxacine. All newly synthesized compounds were screened for their antimicrobial activities and some of them exhibited excellent activity. Moreover, one compound was found to have antiurease activity.