Microwave-assisted linear approach toward highly substituted benzo[d]oxazol-5-yl-1H-benzo[d]imidazole on ionic liquid support

Crystal structure, Hirshfeld surface analysis and DFT studies of 6-bromo-3-(12-bromo-dodec-yl)-2-(4-nitro-phen-yl)-4H-imidazo[4,5-b]pyridine

The title compound, C24H30Br2N4O2, consists of a 2-(4-nitro-phen-yl)-4H-imidazo[4,5-b]pyridine entity with a 12-bromo-dodecyl substituent attached to the pyridine N atom. The middle eight-carbon portion of the side chain is planar to within 0.09 (1) Å and makes a dihedral angle of 21.9 (8)° with the mean plane of the imidazolo-pyridine moiety, giving the mol-ecule a V-shape. In the crystal, the imidazolo-pyridine units are associated through slipped π-π stacking inter-actions together with weak C-HPyr⋯ONtr and C-HBrmdc-yl⋯ONtr (Pyr = pyridine, Ntr = nitro and Brmdcyl = bromo-dodec-yl) hydrogen bonds. The 12-bromo-dodecyl chains overlap with each other between the stacks. The terminal -CH2Br group of the side chain shows disorder over two resolved sites in a 0.902 (3):0.098 (3) ratio. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (48.1%), H⋯Br/Br⋯H (15.0%) and H⋯O/O⋯H (12.8%) inter-actions. The optimized mol-ecular structure, using density functional theory at the B3LYP/ 6-311 G(d,p) level, is compared with the experimentally determined structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Synthesis of 2-Alkoxy/Thioalkoxy Benzo[d]imidazoles and 2-Thione Benzo[d]imidazoles via a Phase-Based, Chemoselective Reaction

2-Alkoxy/thioalkoxy benzo-[d]-imidazole and 2-thione benzo-[d]-imidazole libraries were constructed in solution phase and on solid phase, respectively. The key step in this work is the phase-based chemoselective reaction of the 2-mercaptobenzo-[d]-imidazole intermediate with benzyl chloride (solution phase) and Merrifield resin (solid phase). In the solution-phase case, benzyl chloride reacted with the thiol group of 2-mercaptobenzo-[d]-imidazole, whereas in the solid-phase case, Merrifield resin was introduced at an internal amine group of benzo-[d]-imidazole. To afford the desired 2-alkoxy/thioalkoxy benzo-[d]-imidazole analogues, we used various alkyl halides, alcohols, and thiols in solution phase, and to obtain 2-thione benzo-[d]-imidazole derivatives on solid phase, we used diverse alkyl halides and boronic acids. Finally, to measure the drug potential to be orally active and the molecular diversity in three-dimensional (3D) space, we calculated physicochemical properties and displayed energy-minimized 3D structures. As a result, the libraries from solution phase and solid phase show distinct features in physicochemical properties and skeletal diversities in 3D space.

Diversity oriented synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approach: a critical review

Because of the wide ranging bioactivities associated with the benzimidazole nucleus, this review highlights the advances made in the synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approaches.

Telescoped Synthesis of 2-Acyl-1-aryl-1,2-dihydroisoquinolines and Their Inhibition of the Transcription Factor NF-κB

A sequential single-flask multicomponent reactions is highly effective for the synthesis of 1,2-dihydroisoquinolines through amidealkylation from intermediate N-acylisoquinolinium salts under mild conditions. N-Acylisoquinolinium ions and trichloromethyl-1-(1H-indol-3-yl)isoquinoline-2(1H)-carboxylate have demonstrated their reactivity toward aromatic and aliphatic π-nucleophiles. One of the 1,2-dihydroisoquinoline derivatives was found to be a potent inhibitor for transcription factor NF-κB by blocking IκBα degradation, p65 nuclear translocation, and NF-κB DNA binding in TNF-α-induced NIH 3T3 cells.

Microwave Controlled Reductive Cyclization: A Selective Synthesis of Novel Benzimidazole-alkyloxypyrrolo[1,2-a]quinoxalinones

An efficient cascade synthesis of novel benzimidazole linked alkyloxypyrrolo[1,2-a]quinoxalinones was explored on soluble polymer support under microwave irradiation. Two exclusive protocols have been developed for the partial and full reductive cyclization by controlling the microwave energy. Commencing from the same substrate, ortho nitro pyrrol carboxylates, N-hydroxy pyrroloquinoxalinones were obtained by partial reductive cyclization (60 °C, 7 min), and the synthesis of pyrroloquinoxalinones was accomplished by full reductive cyclization (85 °C, 12 min). This method represents the first synthesis of N-hydroxy pyrroloquinoxalinones using Pd/C and ammonium formate as reducing agents. Further employing a variety of alkyl bromides, the obtained pyrroloquinoxalinones were transformed to their corresponding O- and N-alkylated analogues to deliver the diversified, novel molecular entities.

Rapid two-step synthesis of benzimidazo[1',2':1,5]pyrrolo[2,3-c]isoquinolines by a three-component coupling reaction

A two-step, three-component coupling reaction on ionic liquid supported 2-cyanomethylbenzimidazoles, methyl 2-formylbenzoate, and isocyanides under microwave activation is explored. Knoevenagel condensation of 2-cyanomethylbenzimidazole with methyl-2-formylbenzoate in the presence of piperidine catalyst is followed by [4+1] cycloaddition with an isocyanide in the next step. Consequent intramolecular δ-lactam formation allows rapid construction of novel aza-pentacycles, benzimidazo[1',2':1,5]pyrrolo[2,3-c]isoquinolines.

Parallel and combinatorial liquid-phase synthesis of alkylbiphenyls using pentaerythritol support

Unfunctionalized alkylbiphenyls were fabricated by a parallel and combinatorial synthesis using pentaerythritol as a tetrapodal soluble support for a sulfonate-based traceless multifunctional linker system. Nickel N-heterocyclic carbene-catalyzed reactions of pentaerythritol tetrakis(biphenylsulfonate)s with primary alkylmagnesium bromides generated the alkylbiphenyl derivatives by desulfitative cleavage/cross-coupling of the C-S bond without any "memory" of the attachment on the support. Though the reactions were completed with sufficient yields in 12 h at room temperature, even with only 1.5 equiv of nucleophiles, they still retained the benefits of facile isolation observed in polymer-supported reactions.

Multicomponent solvent-free synthesis of benzimidazolyl imidazo[1,2-a]-pyridine under microwave irradiation

A novel one-pot, three-component reaction employing variously substituted benzimidazole-linked amino pyridines, aldehydes, and isonitriles catalyzed by scandium(III) triflate under solvent-free conditions were accomplished. This new synthetic methodology facilitates the rapid generation of intricate molecular frameworks in three-dimensional fashion leading to benzimidazole-imidazo[1,2-a] pyridines. This approach is envisioned as an environmentally benign process and a simple operation to the biological interesting compounds. The present synthetic sequence permits the introduction of three points of structural diversity to expand chemical space with high purity and excellent yields.