Selective benzopyranone and pyrimido[2,1-a]isoquinolin-4-one inhibitors of DNA-dependent protein kinase: synthesis, structure-activity studies, and radiosensitization of a human tumor cell line in vitro

Modular Assembly of Pyrrolo[3,4-c]isoquinolines through Rh-Catalyzed Cascade C-H Activation/Annulation of O-Methyl Aryloximes with Maleimides

An efficient and practical strategy for the construction of pyrrolo[3,4-c]isoquinolines via Rh(III)-catalyzed cascade C-H activation and subsequential annulation process from easily available O-methyl aryloximes and maleimides has been disclosed. This facile protocol does not require any inert atmosphere protection with good efficiency in a low loading of catalyst and exhibits good functional group tolerance and broad substrate scope. Notably, the as-prepared products show potential photophysical properties.

Discovery, Optimization, and Evaluation of Potent and Selective DNA-PK Inhibitors in Combination with Chemotherapy or Radiotherapy for the Treatment of Malignancies

Given the multifaceted biological functions of DNA-PK encompassing DNA repair pathways and beyond, coupled with the susceptibility of DNA-PK-deficient cells to DNA-damaging agents, significant strides have been made in the pursuit of clinical potential for DNA-PK inhibitors as synergistic adjuncts to chemo- or radiotherapy. Nevertheless, although substantial progress has been made with the discovery of potent inhibitors of DNA-PK, the clinical trial landscape requires even more potent and selective molecules. This necessitates further endeavors to expand the repertoire of clinically accessible DNA-PK inhibitors for the ultimate benefit of patients. Described herein are the obstacles that were encountered and the solutions that were found, which eventually led to the identification of compound 31t. This compound exhibited a remarkable combination of robust potency and exceptional selectivity along with favorable in vivo profiles as substantiated by pharmacokinetic studies in rats and pharmacodynamic assessments in H460, BT474, and A549 xenograft models.

Exploration and biological evaluation of 7-methoxy-3-methyl-1H-chromeno[4,3-c]pyrazol-4-one as an activating transcription factor 3 inducer for managing metabolic syndrome

The induction of activating transcription factor 3 (ATF3) was identified as a promising therapeutic mechanism to overcome metabolic syndrome. Hence, a structure-activity relationship campaign on the chiral lead (1b) was conducted with a scaffold-hopping approach, whereby achiral 7-methoxy-3-methyl-1H-chromeno[4,3-c]pyrazol-4-one (16c) was recognized as a potential ATF3 inducer with a lipid-lowering feature in a pre-differentiated 3T3-L1 cell model. Also, in a high-fat diet scenario, mice subjected to 16c demonstrated robust weight loss with shrinkage of the white adipose mass and fewer hypertrophic adipocytes, accompanied by a preferable glycemic profile compared to 1b. Additionally, the biochemical analysis revealed that 16c further ameliorated the liver function and improved the plasma triglyceride profile that were absent from mice treated with 1b. Taken together, 16c shows promise as an ATF3 stimulant for further development to alleviate metabolic syndrome.

Recent advances in ATM inhibitors as potential therapeutic agents

ATM, a member of the PIKK-like protein family, plays a central role in responding to DNA double-strand breaks and other lesions to protect the genome against DNA damage. Loss of ATM's kinase function has been shown to increase the sensitivity of most cells to ionizing radiation. Therefore, ATM is thought to be a promising target for chemotherapy as a radiotherapy sensitizer. The mechanism of ATM in cancer treatment and the development of its inhibitors have become research hotspots. Here we present an overview of research concerning ATM protein domains, functions and inhibitors, as well as perspectives and insights for future development of ATM-targeting agents.

Direct Carbonylative Difunctional of Terminal Alkynes with Sodium Sulfinates to Access Olefin Sulfonyl Methyl Esters under Metal-Free Conditions

A metal-free difunctional carbonylation procedure toward the synthesis of olefin sulfonyl methyl esters has been developed. By employing easily available terminal alkynes and sodium sulfinates as the starting materials, a...

Targeting DNA repair pathway in cancer: Mechanisms and clinical application

Over the last decades, the growing understanding on DNA damage response (DDR) pathways has broadened the therapeutic landscape in oncology. It is becoming increasingly clear that the genomic instability of cells resulted from deficient DNA damage response contributes to the occurrence of cancer. One the other hand, these defects could also be exploited as a therapeutic opportunity, which is preferentially more deleterious in tumor cells than in normal cells. An expanding repertoire of DDR-targeting agents has rapidly expanded to inhibitors of multiple members involved in DDR pathways, including PARP, ATM, ATR, CHK1, WEE1, and DNA-PK. In this review, we sought to summarize the complex network of DNA repair machinery in cancer cells and discuss the underlying mechanism for the application of DDR inhibitors in cancer. With the past preclinical evidence and ongoing clinical trials, we also provide an overview of the history and current landscape of DDR inhibitors in cancer treatment, with special focus on the combination of DDR-targeted therapies with other cancer treatment strategies.

Natural products from Brazilian biodiversity identified as potential inhibitors of PknA and PknB of M. tuberculosis using molecular modeling tools

Mycobacterium tuberculosis was discovered in 1882 by Robert Koch but, since its discovery, the tuberculosis (TB) epidemic has endured, being one of the top 10 causes of death worldwide. Drug-resistant TB continues to be a public health threat and bioactive compounds with a new mode of action (MoA) are needed to overcome this. Since natural products are described as important sources for the development of new drugs, the objective of this work was to identify potential ligands from Brazilian natural products (NPs) for M. tuberculosis targets using molecular modeling tools. Using chemogenomics we identified the Serine/Threonine Protein Kinase PknB as a putative target for 13 NPs from a database from Brazilian biodiversity (NuBBE). Literature data supported further investigation of NuBBE105, NuBBE598, NuBBE936, NuBBE964, NuBBE1045, and NuBBE1180 by molecular docking and dynamics. Key interactions were observed with PknB and simulations confirmed stability and favorable binding energies. Considering structural similarity with PknB, we further explored binding of the NPs to PknA, critical for M. tuberculosis survival, and all of them resembled important interactions with the enzyme, showing stable and favorable binding energies, whilst van der Waals interactions seem to play a key role for binding to PknA and PknB. NuBBE936 and NuBBE1180 have already had their antimycobacterial activity reported and our results can provide a basis for their MoA. Finally, the other NPs which have not been tested against M. tuberculosis deserve further investigation, aiming at the discovery of antimycobacterial drug candidates with innovative MoA.

Exploiting DNA Damage Repair in Precision Cancer Therapy: BRCA1 as a Prime Therapeutic Target

Simple Summary

Chemical inhibition of central DNA damage repair (DDR) proteins has become a promising approach in precision cancer therapy. In particular, BRCA1 and its DDR-associated proteins constitute important targets for developing DNA repair inhibiting drugs. This review provides relevant insights on DDR biology and pharmacology, aiming to boost the development of more effective DDR targeted therapies.

Abstract

Precision medicine aims to identify specific molecular alterations, such as driver mutations, allowing tailored and effective anticancer therapies. Poly(ADP)-ribose polymerase inhibitors (PARPi) are the prototypical example of targeted therapy, exploiting the inability of cancer cells to repair DNA damage. Following the concept of synthetic lethality, PARPi have gained great relevance, particularly in BRCA1 dysfunctional cancer cells. In fact, BRCA1 mutations culminate in DNA repair defects that can render cancer cells more vulnerable to therapy. However, the efficacy of these drugs has been greatly affected by the occurrence of resistance due to multi-connected DNA repair pathways that may compensate for each other. Hence, the search for additional effective agents targeting DNA damage repair (DDR) is of crucial importance. In this context, BRCA1 has assumed a central role in developing drugs aimed at inhibiting DNA repair activity. Collectively, this review provides an in-depth understanding of the biology and regulatory mechanisms of DDR pathways, highlighting the potential of DDR-associated molecules, particularly BRCA1 and its interconnected partners, in precision cancer medicine. It also affords an overview about what we have achieved and a reflection on how much remains to be done in this field, further addressing encouraging clues for the advance of DDR targeted therapy.

Unusual titanium-induced McMurry coupling of 4-oxo-4H-chromene-2-carbaldehydes enroute to bis-chromones

Ti/Zn-mediated McMurry coupling of a series of 4-oxo-4H-chromene-2-carbaldehydes afforded unusual chemoselective CH₂–CH₂ tethered bis-chromones.

4-Aminocoumarin derivatives: synthesis and applications

4-Aminocoumarins represent an important class of a versatile scaffold in organic synthesis and have been consistently used as a building block in organic chemistry for the synthesis of different heterocyclic compounds.

Synthetic Lethality through the Lens of Medicinal Chemistry

Personalized medicine and therapies represent the goal of modern medicine, as drug discovery strives to move away from one-cure-for-all and makes use of the various targets and biomarkers within differing disease areas. This approach, especially in oncology, is often undermined when the cells make use of alternative survival pathways. As such, acquired resistance is unfortunately common. In order to combat this phenomenon, synthetic lethality is being investigated, making use of existing genetic fragilities within the cancer cell. This Perspective highlights exciting targets within synthetic lethality, (PARP, ATR, ATM, DNA-PKcs, WEE1, CDK12, RAD51, RAD52, and PD-1) and discusses the medicinal chemistry programs being used to interrogate them, the challenges these programs face, and what the future holds for this promising field.

DNA-PK in human malignant disorders: Mechanisms and implications for pharmacological interventions

The DNA-PK holoenzyme is a fundamental element of the DNA damage response machinery (DDR), which is responsible for cellular genomic stability. Consequently, and predictably, over the last decades since its identification and characterization, numerous pre-clinical and clinical studies reported observations correlating aberrant DNA-PK status and activity with cancer onset, progression and responses to therapeutic modalities. Notably, various studies have established in recent years the role of DNA-PK outside the DDR network, corroborating its role as a pleiotropic complex involved in transcriptional programs that operate biologic processes as epithelial to mesenchymal transition (EMT), hypoxia, metabolism, nuclear receptors signaling and inflammatory responses. In particular tumor entities as prostate cancer, immense research efforts assisted mapping and describing the overall signaling networks regulated by DNA-PK that control metastasis and tumor progression. Correspondingly, DNA-PK emerges as an obvious therapeutic target in cancer and data pertaining to various pharmacological approaches have been published, largely in context of combination with DNA-damaging agents (DDAs) that act by inflicting DNA double strand breaks (DSBs). Currently, new generation inhibitors are tested in clinical trials. Several excellent reviews have been published in recent years covering the biology of DNA-PK and its role in cancer. In the current article we are aiming to systematically describe the main findings on DNA-PK signaling in major cancer types, focusing on both preclinical and clinical reports and present a detailed current status of the DNA-PK inhibitors repertoire.

Targeting DNA-PK in cancer

DNA-dependent protein kinase (DNA-PK) is involved in many cellular pathways. It has a key role in the cellular response to DNA damage, in the repair of DNA double-strand break (DNA-DSBs) and as a consequence an important role in maintaining genomic integrity. In addition, DNA-PK has been shown to modulate transcription, to be involved in the development of the immune system and to protect telomeres. These pleotropic involvements and the fact that its expression is de-regulated in cancer have made DNA-PK an intriguing therapeutic target in cancer therapy, especially when combined with agents causing DNA-DSBs such as topoisomerase II inhibitors and ionizing radiation. Different small molecule inhibitors of DNA-PK have been recently synthesized and some are now being tested in clinical trials. This review discusses what is known about DNA-PK, its role in tumor biology, DNA repair and cancer therapy and critically discusses its inhibition as a potential therapeutic approach.

Morpholine as a privileged structure: A review on the medicinal chemistry and pharmacological activity of morpholine containing bioactive molecules

Morpholine is a heterocycle featured in numerous approved and experimental drugs as well as bioactive molecules. It is often employed in the field of medicinal chemistry for its advantageous physicochemical, biological, and metabolic properties, as well as its facile synthetic routes. The morpholine ring is a versatile and readily accessible synthetic building block, it is easily introduced as an amine reagent or can be built according to a variety of available synthetic methodologies. This versatile scaffold, appropriately substituted, possesses a wide range of biological activities. There are many examples of molecular targets of morpholine bioactive in which the significant contribution of the morpholine moiety has been demonstrated; it is an integral component of the pharmacophore for certain enzyme active-site inhibitors whereas it bestows selective affinity for a wide range of receptors. A large body of in vivo studies has demonstrated morpholine's potential to not only increase potency but also provide compounds with desirable drug-like properties and improved pharamacokinetics. In this review we describe the medicinal chemistry/pharmacological activity of morpholine derivatives on various therapeutically related molecular targets, attempting to highlight the importance of the morpholine ring in drug design and development as well as to justify its classification as a privileged structure.

Lowering Lipophilicity by Adding Carbon: One-Carbon Bridges of Morpholines and Piperazines

In this article, we report our investigation of a phenomenon by which bridging morpholines across the ring with one-carbon tethers leads to a counterintuitive reduction in lipophilicity. This effect was also found to occur in piperazines and piperidines and lowered the measured log D_7.4 of the bridged molecules by as much as -0.8 relative to their unbridged counterparts. As lowering lipophilicity without introducing additional heteroatoms can be desirable, we believe this potentially provides a useful tactic to improve the drug-like properties of molecules containing morpholine-, piperazine-, and piperidine-like motifs.

PICT-1 is a key nucleolar sensor in DNA damage response signaling that regulates apoptosis through the RPL11-MDM2-p53 pathway

PICT-1 is an essential ribosome biogenesis factor whose loss induces p53 accumulation and apoptosis. Here, we show that DNA damage changes PICT-1 localization and decreases PICT-1 protein levels via the proteasome pathway. Two important phosphatidylinositol 3-kinase-like kinases (PIKKs), ataxia-telangiectasia mutated (ATM) and the Ku70 subunit of DNA-dependent protein kinase (DNA-PK), co-localize and interact with PICT-1 in the nucleolus. Computational prediction of phosphorylation sites and detection using an anti-phospho-substrate antibody suggest that PICT-1 might be a substrate of PIKKs. PICT-1 S233 and T289 were identified as the key phosphorylation sites in this pathway, as mutating both to alanine abolished UVB-induced increase of PICT-1 phosporylation. Inhibition of PIKKs or ATM (with wortmannin and KU55933, respectively) prevented the agglomeration and degradation of PICT-1, suggesting that ATM is a key regulator of PICT-1. PICT-1(S233A, T289A) demonstrated marked resistance to DNA damage-induced agglomeration and loss of PICT-1. Phosphomimetic PICT-1 (S233D, T289D) showed a different nuclear distribution and was more rapidly degraded after DNA damage than wild-type PICT-1. Furthermore, both phosphorylation and degradation of PICT-1 released RPL11 from the nucleolus to the nucleoplasm, increased binding of RPL11 to MDM2, and promoted p53 accumulation and apoptosis in an ATM-dependent manner after DNA damage. These data indicate that PICT-1 is a major nucleolar sensor of the DNA damage repair response and an important upstream regulator of p53 via the RPL11-MDM2-p53 pathway.

Synthesis of novel fused chromone–pyrimidine hybrids and 2,4,5-trisubstituted pyrimidine derivatives via ANRORC rearrangement

A facile and versatile procedure for the synthesis of functionalized novel 2,5-diphenyl-5H-chromeno[4,3-d]pyrimidin-5-ol and (2,4-diphenylpyrimidin-5-yl) (2-hydroxyphenyl) methanone has been described.

Synthesis of linear and angular aryl-morpholino-naphth-oxazines, their DNA-PK, PI3K, PDE3A and antiplatelet activity

To continue our study of 2-morpholino-benzoxazine based compounds, which show useful activity against PI3K family enzymes or antiplatelet activity, we designed and synthesized a series of linear 6.7-fused, 5,6-angular fused and 7,8-angular fused-aryl-morpholino-naphth-oxazines. The compounds were prepared from substituted 2-hydroxynaphthoic acid to give the corresponding thioxo analogues 8, 9, 15 and 19. The thioxo products were then converted to the morpholino substituted analogue. The aryl group was introduced by Suzuki coupling of bromo precursors. The products were evaluated for activity at PI3K family enzymes and as platelet aggregation inhibitors and compared to reported unsubstituted analogues. The linear 6.7-fused product 13a and 13b were moderated potent but selective PI3Kδ isoform inhibitors (IC₅₀=7.7 and 5.61μM). Good antiplatelet activity was noticed for the angular 7,8-fused compounds 22a, b, k and l with IC₅₀=3.0,14.0, 2.0 and 5.0μM respectively. The antiplatelet activity is independent of PDE3.

Biological importance of structurally diversified chromenes

Compounds incorporating the chromene scaffold are largely present in natural products and display a wide variety of biological activities. Their low toxicity combined to the broad pharmacological properties have inspired medicinal chemists in the search for new therapeutic agents. This review covers the literature between 1993 and on the biological activity of 2H- and 4H-chromenes, both from natural and synthetic origin. Includes a section that identifies a selection of chromene-based natural products, followed by recent literature on bioactive natural chromenes and the corresponding source, covering plants and fruits. Synthetic chromenes are equally important and a separate section addresses the use of these derivatives as new leads for drug discovery. Different biological targets were identified, namely those associated with anticancer, antimicrobial, anti-inflammatory, antithrombotic and antipsychotic activities.

Microwave-Assisted Synthesis of Bioactive Six-Membered Heterocycles and Their Fused Analogues

This review describes the formation of six-membered heterocyclic compounds and their fused analogues under microwave activation using modern organic transformations including cyclocondensation, cycloaddition, multicomponents and other modular reactions. The review is divided according to the main heterocycle types in order of increasing complexity, starting with heterocyclic systems containing one, two and three heteroatoms and their fused analogues. Recent microwave applications are reviewed, with special focus on the chemistry of bioactive compounds. Selected examples from the 2006 to 2015 literature are discussed.

Radio-Sensitization of Human Leukaemic MOLT-4 Cells by DNA-Dependent Protein Kinase Inhibitor, NU7026

In this paper we describe the influence of NU7026, a specific inhibitor of DNA-dependent protein kinase, phosphoinositide 3-kinase, and ATM-kinase on molecular and cellular mechanisms triggered by ionising irradiation in human T-lymphocyte leukaemic MOLT-4 cells. We studied the effect of this inhibitor (10 μM) combined with gammaradiation (1 Gy) leading to DNA damage response and induction of apoptosis. We used methods for apoptosis assessment (cell viability count and flow-cytometric analysis) and cell cycle analysis (DNA content measurement) and we detected expression and post-translational modifications (Western blotting) of proteins involved in DNA repair signalling pathways. Pre-treatment with NU7026 resulted into decreased activation of checkpoint kinase-2 (Thr68), p53 (Ser15and Ser392), and histone H2A.X (Ser139) 2 hours after irradiation. Subsequently, combination of radiation and inhibitor led to decreased amount of cells in G2-phase arrest and into increased apoptosis after 72 hours. Our results indicate that in leukaemic cells the pre-incubation with inhibitor NU7026 followed by low doses of ionising radiation results in radio-sensitising of MOLT-4 cells via diminished DNA repair and delayed but pronounced apoptosis. This novel approach might offer new strategies in combined treatment of leukaemia diseases.

Synthesis of 3-Substituted 2-Aminochromones via Sn(IV)-Promoted Annulation of Ynamides with 2-Methoxyaroyl Chlorides

A Sn(IV)-promoted annulation reaction of ynamides is described for the efficient synthesis of 3-substituted 2-aminochromones under mild conditions. This novel method allows for a concomitant construction of C-C and C-O bonds between ynamides and 2-methoxyaroyl chlorides by a tandem Friedel-Crafts acylation/oxo-Michael addition/elimination strategy.

Synthesis, antitumor activity, and mechanism of action of 6-acrylic phenethyl ester-2-pyranone derivatives

Based on the scaffolds of caffeic acid phenethyl ester (CAPE) as well as bioactive lactone-containing compounds, 6-acrylic phenethyl ester-2-pyranone derivatives were synthesized and evaluated against five tumor cell lines (HeLa, C6, MCF-7, A549, and HSC-2). Most of the new derivatives exhibited moderate to potent cytotoxic activity. Moreover, HeLa cell lines showed higher sensitivity to these compounds. In particular, compound showed potent cytotoxic activity (IC50 = 0.50-3.45 μM) against the five cell lines. Further investigation on the mechanism of action showed that induced apoptosis, arrested the cell cycle at G2/M phases in HeLa cells, and inhibited migration through disruption of the actin cytoskeleton. In addition, ADMET properties were also calculated in silico, and compound showed good ADMET properties with good absorption, low hepatotoxicity, and good solubility, and thus, could easily be bound to carrier proteins, without inhibition of CYP2D6. A structure-activity relationship (SAR) analysis indicated that compounds with ortho-substitution on the benzene ring exhibited obviously increased cytotoxic potency. This study indicated that compound is a promising compound as an antitumor agent.

A domino green method for the rapid synthesis of novel fused isoquinoline derivatives via Knoevenagel/Michael/cyclization reactions on aqueous media and their photophysical properties

An expedient, eco-friendly and green-protocol has been developed for the synthesis of novel 4-imino-2-aryl-4H-pyrido[2,1-a]isoquinoline-3-carbonitrile derivatives via Knoevenagel/Michael/cyclisation reactions in one pot under catalyst-free conditions on aqueous media.

Phosphatidylinositol 3-Kinase (PI3K) and phosphatidylinositol 3-kinase-related kinase (PIKK) inhibitors: importance of the morpholine ring

Phosphatidylinositol 3-kinases (PI3Ks) and phosphatidylinositol 3-kinase-related protein kinases (PIKKs) are two related families of kinases that play key roles in regulation of cell proliferation, metabolism, migration, survival, and responses to diverse stresses including DNA damage. To design novel efficient strategies for treatment of cancer and other diseases, these kinases have been extensively studied. Despite their different nature, these two kinase families have related origin and share very similar kinase domains. Therefore, chemical inhibitors of these kinases usually carry analogous structural motifs. The most common feature of these inhibitors is a critical hydrogen bond to morpholine oxygen, initially present in the early nonspecific PI3K and PIKK inhibitor 3 (LY294002), which served as a valuable chemical tool for development of many additional PI3K and PIKK inhibitors. While several PI3K pathway inhibitors have recently shown promising clinical responses, inhibitors of the DNA damage-related PIKKs remain thus far largely in preclinical development.

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.

Multiplexed DNA repair assays for multiple lesions and multiple doses via transcription inhibition and transcriptional mutagenesis

The capacity to repair different types of DNA damage varies among individuals, making them more or less susceptible to the detrimental health consequences of damage exposures. Current methods for measuring DNA repair capacity (DRC) are relatively labor intensive, often indirect, and usually limited to a single repair pathway. Here, we describe a fluorescence-based multiplex flow-cytometric host cell reactivation assay (FM-HCR) that measures the ability of human cells to repair plasmid reporters, each bearing a different type of DNA damage or different doses of the same type of DNA damage. FM-HCR simultaneously measures repair capacity in any four of the following pathways: nucleotide excision repair, mismatch repair, base excision repair, nonhomologous end joining, homologous recombination, and methylguanine methyltransferase. We show that FM-HCR can measure interindividual DRC differences in a panel of 24 cell lines derived from genetically diverse, apparently healthy individuals, and we show that FM-HCR may be used to identify inhibitors or enhancers of DRC. We further develop a next-generation sequencing-based HCR assay (HCR-Seq) that detects rare transcriptional mutagenesis events due to lesion bypass by RNA polymerase, providing an added dimension to DRC measurements. FM-HCR and HCR-Seq provide powerful tools for exploring relationships among global DRC, disease susceptibility, and optimal treatment.

Emerging challenges in ligand discovery: new opportunities for chromatographic assay

Ligand discovery initiatives are facing interesting challenges as ever-increasing numbers of proteins are entering screening programs. As an answer to steady pressure to improve performance in drug discovery, ligand discovery can expect to play an expanded role in generating small molecules as probes to help uncover the function of novel proteins. Chromatographic assay formats can offer new entry points into standard interaction characterization (binding and rate constants) as well as powerful, scaleable methods for compound screening. This review presents recent advancements in chromatographic assay technology, with a particular focus on frontal affinity chromatography as a platform technology for interaction analysis.

Microwave assisted [RuCl2(p-cymene)2]2 catalyzed regioselective endo-tandem cyclization involving imine and alkyne activation: an approach to benzo[4,5]imidazo[2,1-a]pyridine scaffold

A microwave assisted efficient route to the synthesis of benzimidazole fused heterocycles through metal catalyzed endo-cyclization strategy involving imine and alkyne activation has been developed.