One-pot synthesis of benzo[4,5]imidazo[1,2-a]quinazoline derivatives via facile transition-metal-free tandem process

One-Pot Three-Component Reaction for the Synthesis of 3,4-Dihydroquinazolines and Quinazolin-4(3H)-ones

A highly efficient and straightforward one-pot synthesis of diversely substituted 3,4-dihydroquinazolines and quinazolin-4(3H)-ones has been achieved through a domino three-component assembly reaction of arenediazonium salts, nitriles, and bifunctional aniline derivatives. This new protocol involves three C-N bond formations through the initial formation of N-arylnitrilium intermediates from arenediazonium salts and nitriles, followed by the sequential nucleophilic addition and cyclization reactions with bifunctional anilines, leading to such N-heterocyclic compounds of biological and pharmacological importance. This method offers a simple, expedient, and robust approach with the use of amenable and easily accessible reactants/reagents under metal-free mild conditions, good functional group tolerance, and high efficiency. The synthetic applications were also demonstrated by derivatization of the products obtained from these processes and syntheses of a diverse range of valuable polycyclic N-heterocycles.

Pyrimido[1,2-a]benzimidazoles as inhibitors of oncoproteins ubiquitin specific protease 5 and MYCN in the childhood cancer neuroblastoma

The MYCN oncogene and histone deacetylases (HDACs) are key driver genes in the childhood cancer, neuroblastoma. We recently described a novel pyridobenzimidazole analogue, SE486-11, which enhanced the therapeutic effectiveness of HDAC inhibitors by increasing MYCN ubiquitination through effects on the deubiquitinase, ubiquitin-specific protease 5 (USP5). Here we describe the synthesis of a novel series of pyrimido[1,2-a]benzimidazole derivatives, and an evaluation of their cytopathic effects against non-malignant and human neuroblastoma cell lines. Among the tested analogues, 4-(4-methoxyphenyl)benzo[4,5]imidazo[1,2-a]pyrimidine (3a) was the most active compound against neuroblastoma cells (IC50 ≤ 2 µM), with low cytotoxicity (IC50 ≥ 15 µM) to normal cells. We show compound 3a bound to USP5 protein (Kd = 0.47 µM) in vitro and synergistically enhanced the efficacy of HDAC inhibitors against neuroblastoma cells. Moreover, knockdown of USP5 and MYCN in treated neuroblastoma cells showed that both USP5 and MYCN expression was necessary for the cytopathic activity of compound 3a, thus providing a clinically relevant rationale for further development of this of pyrimido[1,2-a]benzimidazole.

Benzo[4,5]imidazo[1,2-a]pyridines and benzo[4,5]imidazo[1,2-a]pyrimidines: recent advancements in synthesis of two diversely important heterocyclic motifs and their derivatives

Nitrogen heterocycles are some of the most important compounds that are found in nature or synthesized otherwise.

Pyrimido[1,2-a]benzimidazoles: synthesis and perspective of their pharmacological use

The review presents data on the synthesis as well as studies of biological activity of new derivatives of pyrimido[1,2-a]benzimidazoles published over the last decade. The bibliography of the review includes 136 sources.

Access to 2-pyridinylamide and imidazopyridine from 2-fluoropyridine and amidine hydrochloride

Under catalyst-free conditions, an efficient method to synthesize 2-pyridinylamides has been developed, and the protocol uses inexpensive and readily available 2-fluoropyridine and amidine derivatives as the starting materials. Simultaneously, the copper-catalysed approach to imidazopyridine derivatives has been established with high chemoselectivity and regiospecificity. The results suggest that the nitrogen-heterocycles containing iodide substituents can also be compatible for the reaction via the cascade Ullmann-type coupling, and the nucleophilic substitution reaction provides the target products in a one-pot manner.

Preparation of N-Arylquinazolinium Salts via a Cascade Approach

An easy manipulation method for the preparation of N-arylquinazolinium salts is described from readily available aryldiazonium salts, nitriles, and 2-aminoarylketones in a one-pot operation. This method relies on the in situ generation of the N-arylnitrilium intermediate from the reaction of aryldiazonium salt with nitrile, which undergoes amination/cascade cyclization/aromatization, leading to N-arylquinazolinium salts in excellent yields. Nucleophilic addition of alkoxide to these N-arylquinazolinium salts provides functionalized dihydro- N-arylquinazoline.

Synthesis of Pyrimidine- and Quinazoline-Fused Benzimidazole-4,7-diones Using Combinatorial Cyclocondensation and Oxidation

β-Bromo-α,β-unsaturated aldehydes and 2-bromobenzaldehydes react with 4,7-dimethoxy-1H-benzo[d]imidazole-2-amine by microwave irradiation in dimethylformamide in the presence of a base to give the corresponding dimethoxy-substituted benzo[4,5]imidazo[1,2-a]pyrimidines and benzo[4,5]imidazo[1,2-a]quinazolines, respectively, in moderate to good yields. Oxidation of such N-fused hybrid scaffolds by aqueous ceric ammonium nitrate affords pyrimidine- and quinazoline-fused benzimidazole-4,7-diones in high yields.

Aminoazole-Based Diversity-Oriented Synthesis of Heterocycles

The comprehensive review contains the analysis of literature data concerning reactions of heterocyclization of aminoazoles and demonstrates the application of these types of transformations in diversity-oriented synthesis. The review is oriented to wide range of chemists working in the field of organic synthesis and both experimental and theoretical studies of nitrogen-containing heterocycles.

An efficient green synthesis of 5H-spiro[benzo[4,5]imidazo[1,2-c]quinazoline-6,3′-indolin]-2′-ones catalyzed by iodine in ionic liquids

Benzene-1,2-diamine was treated with 2-nitrobenzaldehyde in EtOH, and the product was reduced with hydrazine hydrate in the presence of Fe(C) without separation to give 2-(1

Chemoselective acylation of benzimidazoles with phenylacetic acids under different Cu catalysts to give fused five-membered N-heterocycles or tertiary amides

C-N bond formation via a copper-catalyzed aerobic oxidative decarboxylative tandem protocol was realized. The phenylacetic acids which contain ortho-X (X = F or Br) on the aromatic ring will render a fused five-membered heterocycle via a tandem aromatic nucleophilic substitution and aerobic oxidative decarboxylative acylation at the C(sp(2))-H bond of benzimidazoles under the Cu(OAc)2/K2CO3/BF3·Et2O catalytic system, while with CuBr as the catalyst and pyridine as the base, N-acylation occurred and tertiary amides were obtained.

One-pot three-component synthesis of quinazolines via a copper-catalysed oxidative amination reaction

A copper-catalysed three-component reaction for constructing a series of quinazoline derivatives has been developed.

When Indolizine Meets Quinoline: Diversity-Oriented Synthesis of New Polyheterocycles and Their Optical Properties

Fluorescence-based technologies play a pivotal role in various biomedical applications. Here we report an efficient route to a new class of fluorophores, indolizino[3,2-c]quinolines, via the oxidative Pictet-Spengler cyclization strategy. The condensation of several 2-methylpyridines with 2-bromo-2'-nitroacetophenone allowed for the rapid assembly of indolizines with a 2-nitrophenyl group at the C2 position. The subsequent reduction of the nitro group under mild conditions followed by oxidative Pictet-Spengler cyclization with various aryl aldehydes in the presence of a catalytic amount of FeCl3 furnished the indolizino[3,2-c]quinolines in good overall yields. We also examined the photophysical properties of this new series of polyheterocyclic compounds. Several indolizino[3,2-c]quinolines were found to have unique and desirable optical properties, suggesting that these compounds may be suitable for use as prospective fluorescent probes in aqueous systems.

Efficient synthesis and evaluation of antitumor activities of novel functionalized 1,8-naphthyridine derivatives

An efficient synthesis of novel functionalized 1,8-naphthyridine and chromeno[2,3-b]quinoline derivatives via cascade reaction of 2-chloroquinoline-3-carbaldehyde and enaminones or cyclic 1,3-dicarbonyl compounds was developed. All of the 1,8-naphthyridine derivatives synthesized were evaluated for their antiproliferative properties in vitro against cancer cells and several compounds were found to have high activities.

I2-catalyzed one-pot synthesis of pyrrolo[1,2-a]quinoxaline and imidazo[1,5-a]quinoxaline derivatives via sp3and sp2C–H cross-dehydrogenative coupling

An efficient I₂-catalyzed cascade coupling protocol was developed for the synthesis of pyrrolo[1,2-a]quinoxaline and imidazo[1,5-a]quinoxaline derivativesviasp³and sp²C–H cross-dehydrogenative coupling.