Environmentally friendly and efficient method for the synthesis of the new α , α ′‐diimine ligands with benzimidazole moiety

Synthesis of Morpholine-, Piperidine-, and N-Substituted Piperazine-Coupled 2-(Benzimidazol-2-yl)-3-arylquinoxalines as Novel Potent Antitumor Agents

A novel series of 2-(benzimidazol-2-yl)quinoxalines with three types of pharmacophore groups, namely, piperazine, piperidine, and morpholine moieties, which are part of known antitumor drugs, was designed and synthesized. The compounds have been characterized by NMR and IR spectroscopy, high- and low-resolution mass spectrometry, and X-ray crystallography. 2-(Benzimidazol-2-yl)quinoxalines with N-methylpiperazine substituents showed promising activity against a wide range of cancer lines, without causing hemolysis and showing little cytotoxicity against normal human Wi-38 cells (human fetal lung). A mixture of regioisomers 2-(benzimidazol-2-yl)-3-(4-fluorophenyl)-6(and 7)-(4-methylpiperazin-1-yl)quinoxalines (mri BIQ 13da/14da) showed a highly selective cytotoxic effect against human lung adenocarcinoma (cell line A549) with a half-maximal inhibitory concentration at the level of doxorubicin with a selectivity index of 12. The data obtained by flow cytometry, fluorescence microscopy, and multiparametric fluorescence analysis suggested that the mechanism of the cytotoxic effect of the mri BIQ 13da/14da on A549 cells may be associated with the stopping of the cell cycle in phase S and inhibition of DNA synthesis as well as with the induction of mithochondrial apoptosis. Thus, mri BIQ 13da/14da can be considered as a leading compound deserving further study, optimization, and development as a new anticancer agent.

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