From Bis(imidazol‐2‐yl)methanes to Asymmetrically Substituted Bis(heterocyclo)methanides in Metal Coordination

Crystal structure of 2-{[5-(methyl-sulfan-yl)-4-phenyl-4H-1,2,4-triazol-3-yl]meth-yl}benzo[d]thia-zole

In the structure of the title compound, C17H14N4O2, the triazole ring exhibits inter-planar angles of 63.86 (2) and 76.96 (2)° with the phenyl and benzo-thia-zole planes, respectively. The C-C-C angle at the methyl-ene group is rather wide at 114.28 (4)°. The packing involves three borderline C-H⋯N contacts, two of which combine to form layers parallel to ac, and a pairing of the triazole rings across an inversion centre [inter-planar distance of 3.1852 (2) Å].

A novel approach to bis(1,3-azol-2-yl)acetonitriles and bis(1,3-azol-2-yl)methanes via the [3 + 2]-dipolar cycloaddition of imidazole N-oxides and 2-heteroaryl-3,3-dimethylacrylonitriles

A new synthetic approach for obtaining previously unknown bis(1,3-azol-2-yl)acetonitriles and bis(1,3-azol-2-yl)methanes has been developed. It is based on 1,3-dipolar cycloaddition between 2-unsubstituted imidazole N-oxides and 2-(1,3-azol-2-yl)-3,3-dimethylacrylonitriles, which are easily available through the condensation of (1,3-azol-2-yl)acetonitriles with acetone. The method allows for the construction of various unsymmetric derivatives based on imidazole, oxazole, thiazole, and 1,3,4-thiadiazole cyclic molecules. Its potential has been demonstrated via the synthesis of 24 diverse derivatives with yields of 29-92%. Bis(1,3-azol-2-yl)acetonitriles can be converted to the corresponding bis(1,3-azol-2-yl)methanes via simple acid hydrolysis followed by subsequent spontaneous decarboxylation at nearly quantitative yields.

Mixed Low-Valent Alanes from the Bis(4-methyl-benzoxazol-2-yl)methanide Ligand

Within this work, an aluminum dihydride complex ([(^4-MeBox₂CH)AlH₂]) (1) based on the bis(4-methyl-benzoxazol-2-yl)methanide ligand was synthesized and characterized by spectroscopic methods (NMR, ATR-IR, and fluorescence), DSC (differential scanning calorimetry), mass spectrometry (LIFDI), and single crystal X-ray diffraction. The reactivity of alane 1 was investigated toward the reducing agents [^DippNacNacAl^I] and [(^MesNacNacMg^I)₂], which gave the dialane compounds [(^4-MeBox₂CH)HAl^II-Al^IIH(^DippNacNac)] (2) and [{(^4-MeBox₂CH)Al^IIH}₂] (4a), respectively. Furthermore, dialuminoxanes [{(^4-MeBox₂CH)AlH}₂(μ-O)] (4b) and [({(^MesNacNac)Mg}₂(μ-H)){H₃Al^II-Al^IIH(^4-MeBox₂CH)}] (4c) were isolated as byproducts, with 4b co-crystallizing with 4a. The hydricity of both hydrides in the mixed-ligated dialane 2 were examined by a reaction with 1 equiv of trityl borate ([Ph₃C][B(C₆F₅)₄]), which resulted in [(^4-MeBox₂CH)HAl^II-Al^II(^DippNacNac)][B(C₆F₅)₄] (3). Due to the formation of 4b, complex 1 was reacted with 0.5 equiv of water, which causes the likely synthesis of insoluble oligomeric alumoxanes. To prevent this reaction and support the formation of well-defined dialumoxanes, 1 was initially converted to [(^4-MeBox₂CH)(DippO)AlH] (5) by the deprotonation of 2,6-diisopropylphenol (propofol). This sterically encumbered compound 5 was subsequently reacted with 0.5 equiv of water, which resulted in defined molecules of [{(^4-MeBox₂CH)(DippO)Al}₂(μ-O)] (6). All these compounds exemplify the versatility of the ^4-MeBox₂CH ligand in low-valent aluminum chemistry.

An efficient synthesis of novel di-heterocyclic benzazole derivatives and evaluation of their antiproliferative activities

A series of unsymmetrical nine di-heterocyclic compounds of benzazole derivatives were synthesized at one step via cyclization reaction. The compounds evaluated for in vitro cytotoxic activity against A549, A498, HeLa, and HepG2 cancer cell lines. The biological evaluation results show that 23, 26 and 29 exhibit better activity against HepG2 and HeLa cancer cell lines. Compound 23 also showed good activity against A549, and A498 cancer cell lines. The analogs were further performed molecular docking studies against human cytochrome P450 2C8 monooxygenase enzyme, calculated some theoretical quantum parameters, ADMET descriptor and molecular electrostatic potential analysis. The strategy applied in this research work may act as a perspective for the rational design of potential anticancer drugs. Communicated by Ramaswamy H. Sarma.

A Water-Containing Organopotassium Compound Based on Bis(4,6-tBu-benzoxazol-2-yl)methanide and Its Unexpected Stability to Hydrolysis

The bulky bis(4,6-tBu-benzoxazol-2-yl)methane ligand system enabled the synthesis of the water-containing organometallic potassium complex [(18-crown-6)K{(4,6-tBu-OCNC₆ H₂ )₂ CH}⋅H₂ O] (2), which is an unprecedented example of a water-stable reactive organopotassium compound. Furthermore, 2 is a rare example of a bis(benzoxazol-2-yl)methanide ligand displaying solely O-coordination to a metal ion. Compound 2 was fully characterized through its solid-state structure. Furthermore, its behavior in solution was investigated by NMR titration DOSY experiments. These revealed full protonation of the complex only after seven days and the addition of 114 equivalents of water.

A Novel Bulky Heteroaromatic-Substituted Methanide Mimicking NacNac: Bis(4,6-tert-butylbenzoxazol-2-yl)methanide in s-Block Metal Coordination

A novel bulky bis(4,6-tBu-benzoxazol-2-yl)methane ligand was synthesized in a straightforward three-step synthesis. The corresponding complexes [Li{(4,6-tBu-NCOC₆ H₂ )₂ CH}THF], [K{η⁵ -(4,6-tBu-NCOC₆ H₂ )₂ CH}]_∞ , and [MgCl{(4,6-tBu-NCOC₆ H₂ )₂ CH}(THF)₂ ] were obtained upon metalation with alkaline or alkaline-earth-metal reagents. Reduction of [MgCl{(4,6-tBu-NCOC₆ H₂ )₂ CH}(THF)₂ ] with potassium metal or KC₈ led to the formation of the homoleptic compound [Mg{(4,6-tBu-NCOC₆ H₂ )₂ CH}₂ ]. All compounds were fully characterized. Their solid-state structures as well as their behavior in solution, which was analyzed with the help of advanced NMR spectroscopic techniques, are discussed in detail.