Improved and ligand-free copper-catalyzed cyclization for an efficient synthesis of benzimidazoles from o-bromoarylamine and nitriles

We present an improved copper-catalyzed cyclization for an efficient synthesis of benzimidazoles from o-bromoarylamine and nitriles, under mild and ligand-free conditions. The optimal conditions yielded exceptional products of up to 98%, demonstrating the broad applicability of this synthetic strategy in generating a wide range of valuable imidazole derivatives. This methodology enables the efficient synthesis of various substituted benzimidazole derivatives and offers an environmentally friendly alternative to conventional methods. By eliminating the use of harsh reagents and high temperatures associated with traditional synthesis approaches, this method proves to be more efficient and robust. Notably, we successfully applied this synthetic approach to the synthesis of bendazol and thiabendazole, yielding 82% and 78%, respectively, on a 100 gram scale.

Synthesis, Antimicrobial and Antibiofilm Activities, and Molecular Docking Investigations of 2-(1H-Indol-3-yl)-1H-benzo[d]imidazole Derivatives

The treatment of many bacterial and fungal infections remains a problem due to increasing antibiotic resistance and biofilm formation by pathogens. In the present article, a methodology for the chemoselective synthesis of 2-(1H-indol-3-yl)-1H-benzo[d]imidazole derivatives is presented. We report on the antimicrobial activity of synthesized 2-(1H-indol-3-yl)-1H-benzo[d]imidazoles with significant activity against Staphylococcus aureus ATCC 25923, Staphylococcus aureus ATCC 43300 (MRSA), Mycobacterium smegmatis (mc(2)155/ATCC 700084), and Candida albicans ATCC 10231. High activity against staphylococci was shown by indolylbenzo[d]imidazoles 3ao and 3aq (minimum inhibitory concentration (MIC) < 1 µg/mL) and 3aa and 3ad (MIC 3.9-7.8 µg/mL). A low MIC was demonstrated by 2-(1H-indol-3-yl)-1-methyl-1H-benzo[d]imidazole (3ag) against M. smegmatis and against C. albicans (3.9 µg/mL and 3.9 µg/mL, respectively). 2-(5-Bromo-1H-indol-3-yl)-6,7-dimethyl-1H-benzo[d]imidazole (3aq) showed a low MIC of 3.9 µg/mL against C. albicans. Compounds 3aa, 3ad, 3ao, and 3aq exhibited excellent antibiofilm activity, inhibiting biofilm formation and killing cells in mature biofilms. Molecular docking analysis identified three potential interaction models for the investigated compounds, implicating (p)ppGpp synthetases/hydrolases, FtsZ proteins, or pyruvate kinases in their antibacterial action mechanism.

Recent advancements on Benzimidazole: A versatile scaffold in medicinal chemistry

Benzimidazole is nitrogen containing fused heterocycle which has been extensively explored in medicinal chemistry. Benzimidizole nucleus has been found to possess various biological activities such as anticancer, antimicrobial, anti-inflammatory, antiviral, antitubercular and antidiabetic. A number of benzimidazoles such as bendamustine, pantoprazole have been approved for the treatment of various illnesses whereas galeterone and GSK461364 are in clinical trials. The present review article gives an overview about the different biological activities exhibited by the benzimidazole derivatives as well as different methods used for the synthesis of benzimidazole derivatives for the past ten years.

Potassium tert-butoxide mediated C-C, C-N, C-O and C-S bond forming reactions

Potassium tertiary butoxide (KO^tBu) mediated constructions of C-C, C-O, C-N, and C-S bonds are reviewed with special emphasis on their synthetic applications. KO^tBu can be used to perform reactions already known to be carried out using transition metals, but it has advantages in terms of environmental congruence and economic cost. KO^tBu is widely employed in organic synthesis to mediate the construction of C-C, C-O, C-N, C-S and miscellaneous bonds in good to excellent yields. Synthetic uses of KO^tBu in coupling, alkylation, arylation, α-phenylation, cyclization, Heck-type, annulation, photo-arylation, aromatic-substitution, amidation, and silylation reactions are summarized and discussed. The mechanisms through which KO^tBu carries out a specific reaction are also discussed. One of the goals of this review is to attract the attention of chemists as to the benefits of using KO^tBu as an environmentally benign alternative to transition metals and its applications in the construction of chemical bonds with predominant importance in organic synthesis. This review completely covers the synthetic protocols that have been performed using KO^tBu in the last two decades.

An improved synthesis of telmisartan via the copper-catalyzed cyclization of o-haloarylamidines

A concise synthetic route was designed for making telmisartan. The key bis-benzimidazole structure was constructed via the copper-catalyzed cyclization of o-haloarylamidines. By adopting this approach, telmisartan was obtained in a 7-step overall yield of 54% starting from commercially available 3-methyl-4-nitrobenzoic acid, and the use of HNO₃/H₂SO₄ for nitration and polyphosphoric acid (PPA) for cyclization in the reported literatures were avoided.

A concise synthetic route of telmisartan was developed via the copper-catalyzed cyclization of o-haloarylamidines, avoiding the use of HNO₃/H₂SO₄ and polyphosphoric acid (PPA).

Synthesis of benzimidazoles by CuI-catalyzed three-component reaction of 2-haloaniline, ammonia and aldehyde in water

An efficient copper-catalyzed three-component reaction of 2-haloaniline, ammonia and aldehyde for the synthesis of benzimidazoles with 1,10-phenanthroline as the ligand has been developed. A variety of substituted benzimidazole derivatives can be obtained in yields up to 95%.

Synergic effect of copper-based metal–organic frameworks for highly efficient C–H activation of amidines

A Cu–MOF-catalyzed C–H functionalization of substituted amidines was developed for the facile and efficient synthesis of benzimidazoles.

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.

Transition-metal free synthesis of quinazolinones via tandem cyclization of 2-halobenzoic acids with amidines

A simple protocol for the synthesis of quinazoline-4(3H)-ones by tandem cyclization of 2-halobenzoic acids with amidines has been developed by using KOH as a base in DMSO at 120 °C.

Synthesis of 1,4-dihydroquinoline derivatives under transition-metal-free conditions and their diverse applications

A transition-metal-free process for the synthesis of 1,4-dihydroquinoline derivatives starting from simple enaminones with aldehydes via intermolecular cascade cyclization in a one-pot protocol is developed. This methodology affords a variety of products in moderate to good yields. Particularly, the use of the enaminone fragment in 1,4-dihydroquinoline derivatives 3 as a leaving group for further diverse applications with C-nucleophiles is proved to be feasible.

A highly efficient oxidative condensation reaction for selective protein conjugation

A novel oxidative conjugation reaction between aryl diamine and aldehyde was used to site-specifically label a protein.

Metal catalyst free one-pot synthesis of 2-arylbenzimidazoles from α-aroylketene dithioacetals

An efficient green synthetic approach has been developed towards the synthesis of 2-aryl substituted benzimidazoles 4 from α-aroylketene dithioacetals (AKDTAs) 1 and phenylenediamine (OPD) 2.

Transition-metal-free synthesis of benzimidazoles mediated by KOH/DMSO

Benzimidazoles are prepared by intramolecular N-arylations of amidines mediated by potassium hydroxide in DMSO at 120 °C. In this manner, diversely substituted products have been obtained in moderate to very good yields.