Synthesis and affinity to DNA of phenylbenzoimidazoles and benzoimidazo[1,2-c]quinazolines

Cp*CoIII-catalyzed formal [4 + 2] cycloaddition of 2-phenyl-1H-imidazoles to afford imidazo[1,2-c]quinazoline derivatives

A synthetic protocol based on Cp*Co^III-catalyzed C-H amidation/annulation of 2-aryl-1H-imidazoles with 1,4,2-dioxazol-5-ones was developed to give imidazo[1,2-c]quinazoline derivatives with broad substrate scope in moderate to good yields. The method has good prospects of application in the synthesis of imidazo[1,2-c]quinazoline drugs.

Recent Developments Towards Synthesis of (Het)arylbenzimidazoles

Benzimidazole is an important heterocycle that is widely researched and utilized by the pharmaceutical industry and is one of the five most commonly used five-membered aromatic heterocyclic compounds approved by the US Food and Drug Administration. In view of their wide-ranging bioactivities, systems containing benzimidazole as one of the moieties occupy a special place among other benzimidazole derivatives. Since 2010, many improved synthetic strategies have been developed for the construction of hetaryl- and arylbenzimidazole molecular scaffolds under environmentally benign conditions. This review emphasizes the recent trends and modifications frequently used in the synthesis of derivatives of benzimidazole such as the Phillips–Ladenburg and Weidenhagen reactions, as well as entirely new methods of synthesis, involving oxidative cyclization, cross-coupling, ring distortion strategy, and rearrangements carried out under environmentally benign conditions.

1 Introduction

2 From 1,2-Diaminobenzenes with Various One-Carbon Unit Suppliers

2.1 Phillips–Ladenburg Reaction

2.1.1 With (Het)arenecarboxylic Acids

2.2.2 With (Het)arenecarboxylic Acid Derivatives

2.2 Weidenhagen Reaction

2.2.1 With (Het)arenecarbaldehydes or (Het)aryl Methyl Ketones

2.2.2 With Primary Alcohols

2.2.3 With Primary Alkylamines

2.2.4 With 2-Methylazaarenes

2.2.5 With Other One-Carbon Fragment Suppliers

3 From 2-Haloacetanilides and Amines

4 From Amidines

5 From Tetrahydroquinazolines

6 Mamedov Rearrangement

7 Conclusions and Outlook

Rh(III)-Catalyzed One-Pot Synthesis of Benzimidazoquinazolines via C-H Amidation-Cyclization of N-LG-2-phenylbenzoimidazoles

An efficient protocol to synthesize substituted benzo[4,5]imidazo[1,2- c]quinazolines starting from N-LG-2-phenylbenzoimidazole and dioxazolones catalyzed by Rh(III) or Ir(III) has been developed. Various substituted benzo[4,5]imidazo[1,2- c]quinazolines could be easily provided in up to 99% yield. A large range of substrates and functional groups are compatible for this transformation. This method features low catalyst loading, acid-free conditions, and low solvent consumption.

I2-Catalyzed Oxidative Cross-Coupling Reaction of Methyl Ketones and 2-(2-Aminophenyl) Benzimidazole: Facile Access to Benzimidazo[1,2-c]quinazoline

A general and efficient iodine-catalyzed metal-free oxidative cross-coupling reaction of methyl ketones with 2-(1H-benzo[d]imidazol-2-yl)aniline has been established. This is a new synthetic strategy for the synthesis of benzimidazo[1,2-c]quinazoline derivatives involving C(sp³)-H oxidation, condensation, and cyclization processes.

Different positions of amide side chains on the benzimidazo[1,2-a]quinoline skeleton strongly influence biological activity

Benzimidazo[1,2-a]quinolines substituted with amide chains have been evaluated for their antiproliferative, antibacterial and antiviral activity in vitro.

An efficient one-pot two catalyst system in the construction of 2-substituted benzimidazoles: synthesis of benzimidazo[1,2-c]quinazolines

The benzimidazole core is a common moiety in a large number of natural products and pharmacologically active small molecules. The synthesis of novel benzimidazole derivatives remains a main focus in medicinal research. In continuation of the efforts towards Ce(III) catalysts for organic transformations, we observed for the first time the activity of the iodide ion and copper cation in activating CeCl3·7H2O in the selective formation of prototypical 2-substituted benzimidazoles. The one-pot CeCl3·7H2O-CuI catalytic system procedure includes the cyclo-dehydrogenation of aniline Schiff's bases, generated in situ from the condensation of 1,2-phenylenediamine and aldehydes, followed by the oxidation with iodine, which works as a hydrogen sponge. Mild reaction conditions, good to excellent yields, and clean reactions make the procedure a useful contribution to the synthesis of biologically active fused heterocycles containing benzimidazoquinazolines.

The Conversion of 4-Anilinoquinazoline- and 3-Aryl-4-imino-3,4-dihydro-quinazoline-2-carbonitriles into Benzo[4,5]imidazo[1,2-c]quinazoline-6-carbonitriles via Oxidative and Nonoxidative C-N Couplings

Benzo[4,5]imidazo[1,2-c]quinazoline-6-carbonitriles are prepared in high yields via three new routes: (1) a Cu(OTf)2 (0-5 mol %) catalyzed hypervalent iodine [PhI(OTf)2] mediated oxidative coupling of 4-anilinoquinazoline-2-carbonitriles in neat trifluoroacetic acid (TFA); (2) a Pd(OAc)2 (10 mol %) or CuI (10 mol %) mediated nonoxidative coupling of 4-(2-bromoanilino)quinazoline-2-carbonitrile; and (3) a nonoxidative Pd(Ar3P)3 [Ar = 3,5-(F3C)2C6H3] [aka Superstable Pd(0) Catalyst] (10 mol %) mediated intramolecular C-N cyclization of 3-(2-bromophenyl)-4-imino-3,4-dihydroquinazoline-2-carbonitriles. All new compounds are fully characterized.

Copper-mediated aerobic oxidative synthesis of benzimidazo fused quinazolines via a multicomponent approach

First copper mediated aerobic oxidative multi-component synthesis of benzimidazo[1,2-c]quinazolines has been developed from 2-(2-halophenyl)benzoimidazoles, aldehydes and sodium azide as nitrogen source.

Synthesis, antiproliferative activity and DNA binding properties of novel 5-aminobenzimidazo[1,2-a]quinoline-6-carbonitriles

The synthesis of 5-amino substituted benzimidazo[1,2-a]quinolines prepared by microwave assisted amination from halogeno substituted precursor was described. The majority of compounds were active at micromolar concentrations against colon, lung and breast carcinoma cell lines in vitro. The N,N-dimethylaminopropyl 9 and piperazinyl substituted derivative 19 showed the most pronounced activity towards all of the three tested tumor cell lines, which could be correlated to the presence of another N heteroatom and its potential interactions with biological targets. The DNA binding studies, consisting of UV/Visible absorbency, melting temperature studies, and fluorescence and circular dichroism titrations, revealed that compounds 9, 19 and 20 bind to DNA as strong intercalators. The cellular distribution analysis, based on compounds' intrinsic fluorescence, showed that compound 20 does not enter the cell, while compounds 9 and 19 do, which is in agreement with their cytotoxic effects. Compound 9 efficiently targets the nucleus whereas 19, which also showed DNA intercalating properties in vitro, was mostly localised in the cytoplasm suggesting that the antitumor mechanism of action is DNA-independent.

Relay recognition of Cu2+ and S2- in water by a simple 2-(2'-aminophenyl)benzimidazole derivatized fluorescent sensor through modulating ESIPT

A new 2-(2'-aminophenyl)benzimidazole (2-APBI) derivatized fluorescent sensor (L) that behaves relay recognition of Cu(2+) and S(2-) in water solution (pH 7.4) has been developed. Sensor L displays excited-state intramolecular proton transfer (ESIPT) featured two emission bands and performs highly selective and sensitive recognition to Cu(2+) through two emissions simultaneous quenching. The on-site formed L-Cu(2+) complex exhibits excellent selectivity to S(2-) with fluorescence "off-on" response via Cu(2+) displacement approach, which exerts ESIPT recovery. Thus, through modulation the ESIPT state of sensor L, relay recognition of Cu(2+) and S(2-) in water has been achieved.

Synthesis and activity evaluation of tilorone analogs as potential anticancer agents

Tilorone is an interferon inducer with anticancer activity. Twenty-two novel tilorone analogs were synthesized by improvements of fluorenone skeleton, side chains and amino groups to screen new anticancer agents. In vitro evaluation showed that ten new compounds had better anticancer activities than tilorone. Among them, 2c (IC50 < 7 μM against cancer cell lines and IC50 > 35 μM against non-cancer cell lines) and 5d (IC50 < 10 μM against cancer cell lines and IC50 > 53 μM against non-cancer cell lines) exhibited the best anticancer activities and selectivities. Pharmacophore modeling of highly active compounds was carried out by Molecular Operating Environment (MOE) to generate a visualized model for compound design in future study.

Discovery of benzimidazole derivatives as novel multi-target EGFR, VEGFR-2 and PDGFR kinase inhibitors

Multi-target EGFR, VEGFR-2 and PDGFR inhibitors are highly useful anticancer agents with improved therapeutic efficacies. In this work, we used two virtual screening methods, support vector machines (SVM) and molecular docking, to identify a novel series of benzimidazole derivatives, 2-aryl benzimidazole compounds, as multi-target EGFR, VEGFR-2 and PDGFR inhibitors. 2-Aryl benzimidazole compounds were synthesized and their biological activities against a tumor cell line HepG-2 and specific kinases were evaluated. Among these compounds, compounds 5a and 5e exhibited high cytotoxicity against HepG-2 cells with IC₅₀ values at ∼2 μM. Further kinase assay study showed that compound 5a have good EGFR inhibitory activity and moderate VEGFR-2 and PDGFR inhibitory activities, while 5e have moderate EGFR inhibitory activity and slightly weaker VEGFR-2 and PDGFR inhibitory activities. Molecular docking analysis suggested that compound 5a more tightly interacts with EGFR and PDGFR than compound 5e. Our study discovered a novel series of benzimidazole derivatives as multi-target EGFR, VEGFR-2 and PDGFR kinases inhibitors.

Copper-catalyzed cascade synthesis of benzimidazoquinazoline derivatives under mild condition

An efficient copper-catalyzed cascade method has been developed for the synthesis of benzimidazoquinazoline derivatives via reactions of readily available substituted 2-(2-halophenyl)benzoimidazoles with amidines or guanidine under mild conditions (even at room temperature).