Antitumor Activity of New Substituted 3-(5-Imidazo[2,1-b]thiazolylmethylene)-2-indolinones and Study of Their Effect on the Cell Cycle

Green Synthesis of Electrophilic Alkenes Using a Magnesium Catalyst under Aqueous Conditions and Mechanistic Insights by Density Functional Theory

A green approach for the synthesis of electrophilic alkenes has been developed via Knoevenagel condensation between active methylene compounds and carbonyl compounds using Mg powder under aqueous conditions. In this strategy, Mg(OH)2 acts as a catalyst, which was generated in situ by the reaction between metallic Mg (20 mol %) and water. Mg was found to be an efficient, nontoxic, and inexpensive metal catalyst system for producing a range of electrophilic alkenes in excellent yields (≤98%). A gram-scale synthesis of electrophilic alkenes has been developed, and Mg metal was recovered and recycled up to three times without an appreciable loss of catalytic activity. A catalytic cycle was proposed, and the reaction mechanism was investigated using density functional theory. The key steps are enolization of ethyl cyanoacetate, C-C bond formation, and then regeneration of the catalyst via metathesis with H2O. The overall reaction occurs easily with a maximum ΔG°⧧ value of 7.9 kcal/mol for the rate-determining C-C bond formation step. Our protocol has several advantages and can be further extended to one-pot sequential Knoevenagel condensation and Michael addition, and one-pot sequential Knoevenagel condensation and chemoselective reduction can be used for the synthesis of valuable precursors of pharmaceutical products under green and aqueous conditions.

New imidazo[2,1-b]thiazole-based aryl hydrazones: unravelling their synthesis and antiproliferative and apoptosis-inducing potential

Herein, we have designed and synthesized new imidazo[2,1-b]thiazole-based aryl hydrazones (9a-w) and evaluated their anti-proliferative potential against a panel of human cancer cell lines. Among the synthesized compounds, 9i and 9m elicited promising cytotoxicity against the breast cancer cell line MDA-MB-231 with IC50 values of 1.65 and 1.12 μM, respectively. Cell cycle analysis revealed that 9i and 9m significantly arrest MDA-MB-231 cells in the G0/G1 phase. In addition, detailed biological studies such as annexin V-FITC/propidium iodide, DCFH-DA, JC-1 and DAPI staining assays revealed that 9i and 9m triggered apoptosis in MDA-MB-213 cells. Overall, the current work demonstrated the cytotoxicity and apoptosis-inducing potential of 9i and 9m in breast cancer cells and suggested that they could be explored as promising antiproliferative leads in the future.

Cyclization of Thiopropargyl Benzimidazoles by Combining Iron(III) Chloride and Diorganyl Diselenides

A practical synthetic approach to the synthesis of 3-(organoselenyl)-imidazothiazines was developed. The methodology involved the regioselective 6-endo-dig cyclization of thiopropargyl benzimidazoles promoted by diorganyl diselenides and iron(III) chloride. The investigation to determine the best reaction conditions indicated the use of thiopropargyl benzimidazoles (0.25 mmol) with diorganyl diselenides (1.0 equiv) and iron(III) chloride (2.0 equiv) in dichloromethane at 40 °C for 30 min to be optimal. Under these conditions, the scope of the substrates was evaluated varying the structures of thiopropargyl benzimidazoles and diorganyl diselenides giving 28 3-(organoselenyl)-imidazothiazines in moderate to good yields. The reaction conditions were also applicable to diorganyl ditellurides; however, they did not work for diorganyl disulfides. The mechanism studies were carried out indicating that the cyclization proceeds via a cooperative action of diorganyl diselenides and iron(III) chloride, but a direct electrophilic cyclization, promoted by the in situ formed electrophilic organoselenium species, cannot be ruled out.

A Comprehensive Review on the Therapeutic Versatility of Imidazo [2,1-b]thiazoles

BACKGROUND

Imidazo[2,1-b]thiazole, a well-known fused five-membered hetrocycle is one of the most promising and versatile moieties in the area of medicinal chemistry. Derivatives of imidazo[2,1-b]thiazole have been investigated for the development of new derivatives that exhibit diverse pharmacological activities. This fused heterocycle is also a part of a number of therapeutic agents.

OBJECTIVE

To review the extensive pharmacological activities of imidazo[2,1-b]thiazole derivatives and the new molecules developed between 2000-2018 and their usefulness.

METHOD

Thorough literature review of all relevant papers and patents was conducted.

CONCLUSION

The present review, covering a number of aspects, is expected to provide useful insights in the design of imidazo[2,1-b]thiazole-based compounds and would inspire the medicinal chemists for a comprehensive and target-oriented information to achieve a major breakthrough in the development of clinically viable candidates.

One-step construction of complex polyheterocycles via a sequential post-GBB cyclization/spiro ring expansion triggered by a [1,5]-hydride shift

An efficient tandem route to novel amino-indazolo[3′,2′:2,3]imidazo[1,5-c]quinazolin-6(5H)-ones has been explored.

An approach towards the synthesis of novel fused nitrogen tricyclic heterocyclic scaffolds via GBB reaction

A concise and efficient one-pot synthesis of novel N-fused tricyclic derivatives has been developed by using the Groebke–Blackburn–Bienaymé (GBB) reaction, which involved the reaction of 3-amino-1H-indazoles, aldehydes and isonitriles to afford 2-aryl-5H-imidazo[1,2-b]indazol-3-amine derivatives via a formal [4 + 1] cycloaddition reaction.

Expedient synthesis of a phenanthro-imidazo-pyridine fused heteropolynuclear framework via CDC coupling: a new class of luminophores

We herein report the design and synthesis of a group of fused phenanthro-imidazo[1,2-a]pyridine derivatives as a new class of luminescent materials through a Pd(ii) catalyzed intramolecular CDC coupling.

Regioselective Suzuki–Miyaura reactions of 4,7-dichloro-N-methylisatin. Synthesis, anti-HIV activity and modeling study

Suzuki–Miyaura reactions of 4,7-dichloro-N-methylisatin provide a convenient access to arylated methylisatins.

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.

2-(1,3-Benzodioxol-5-yl)-1H-benzimidazole

The asymmetric unit of the title compound, C14H10N2O2, contains two independent molecules. In each molecule, the benzodioxole ring system displays an envelope conformation, with the methylene C atom located at the flap deviating by 0.081 (2) and 0.230 (2) Å from the mean plane formed by the other atoms. The dihedral angles between the benzoimidazole ring system (all atoms) and the benzodioxole benzene ring are 15.35 (6) and 10.99 (7)°. In the crystal, molecules are linked by N—H...N hydrogen bonds into chains running along the [101].

Synthesis of imidazothiadiazole–benzimidazole conjugates as mitochondrial apoptosis inducers

A series of imidazothiadiazole–benzimidazole conjugates (3a–z) were synthesized and evaluated for their cytotoxic activity against a set of four selected human cancer cell lines. Compounds3band3yexhibited significant antiproliferative activity against the ME-180 (cervical) cell line.

One-pot, two-step synthesis of imidazo[1,2-a]benzimidazoles via a multicomponent [4 + 1] cycloaddition reaction

A one-pot, two-step synthesis of imidazo[1,2-a]benzimidazoles has been achieved by a three-component reaction of 2-aminobenzimidazoles with an aromatic aldehyde and an isocyanide. The reaction involving condensation of 2-aminobenzimidazole with an aldehyde is run under microwave activation to generate an imine intermediate under basic conditions which then undergoes [4 + 1] cycloaddition with an isocyanide.

Purified brominated indole derivatives from Dicathais orbita induce apoptosis and cell cycle arrest in colorectal cancer cell lines

Dicathais orbita is a large Australian marine gastropod known to produce bioactive compounds with anticancer properties. In this research, we used bioassay guided fractionation from the egg mass extract of D. orbita using flash column chromatography and identified fractions containing tyrindoleninone and 6-bromoisatin as the most active against colon cancer cells HT29 and Caco-2. Liquid chromatography coupled with mass spectrometry (LCMS) and 1H NMR were used to characterize the purity and chemical composition of the isolated compounds. An MTT assay was used to determine effects on cell viability. Necrosis and apoptosis induction using caspase/LDH assay and flow cytometry (PI/Annexin-V) and cell cycle analysis were also investigated. Our results show that semi-purified 6-bromoisatin had the highest anti-cancer activity by inhibiting cell viability (IC50 = ~100 µM) and increasing caspase 3/7 activity in both of the cell lines at low concentration. The fraction containing 6-bromoisatin induced 77.6% apoptosis and arrested 25.7% of the cells in G2/M phase of cell cycle in HT29 cells. Tyrindoleninone was less potent but significantly decreased the viability of HT29 cells at IC50 = 390 µM and induced apoptosis at 195 µM by increasing caspase 3/7 activity in these cells. This research will facilitate the development of these molluscan natural products as novel complementary medicines for colorectal cancer.

3-(2-Bromo-phen-yl)thia-zolo[3,2-a]benzimidazole

The title compound, C₁₅H₉BrN₂S, was prepared by the reaction of 1-bromo-2-(2,2-dibromo­vin­yl)benzene with 1H-benzo[d]imidazole-2(3H)-thione. The thia­zolo[3,2-a]benz­imidazole fused-ring system is nearly planar, the maximum atomic deviation being 0.049 (4) Å. This mean plane is oriented at a dihedral angle of 71.55 (17)° with respect ot the bromo­phenyl ring. π–π stacking is observed in the crystal structure, the centroid–centroid distance between the thia­zole and imidazole rings of adjacent mol­ecules being 3.582 (2) Å.

Synthesis of imidazothiazole-chalcone derivatives as anticancer and apoptosis inducing agents

A new class of imidazo[2,1-b]thiazole chalcone derivatives were synthesized and evaluated for their anticancer activity. These chalcone derivatives show promising activity, with log GI(50) values ranging from -7.51 to -4.00. The detailed biological aspects of these derivatives toward the MCF-7 cell line were studied. Interestingly, these chalcone derivatives induced G(0)/G(1)-phase cell-cycle arrest, down-regulation of G(1)-phase cell-cycle regulatory proteins such as cyclin D1 and cyclin E1, and up-regulation of CDK4. Moreover, these compounds elicit the characteristic features of apoptosis such as enhancement in the levels of p53, p21, and p27, suppression of NF-κB, and up-regulation of caspase-9. One of these chalcone derivatives, 3 d, is potentially well suited for detailed biological studies, either alone or in combination with existing therapies.

Copper-catalyzed synthesis of N-fused heterocycles through regioselective 1,2-aminothiolation of 1,1-dibromoalkenes

The first aminothiolation of 1,1-dibromoalkene is described using an inexpensive copper/N,N-dimethylethylenediamine catalyst. The method provides a powerful means of using easily available 1,1-dihaloalkenes as precursors to fused heterocycles.

Antitumor activity of new substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and 3-(5-imidazo[2,1-b]thiadiazolylmethylene)-2-indolinones: selectivity against colon tumor cells and effect on cell cycle-related events

The synthesis of new 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and 3-(5-imidazo[2,1-b]thiadiazolylmethylene)-2-indolinones is reported. The antitumor activity was evaluated according to the protocols available at the National Cancer Institute (NCI), Bethesda, MD. To investigate the mechanism of action of the most potent antitumor agent of this series, its effect on growth of HT-29 colon carcinoma cells was studied. Its ability to inhibit cellular proliferation was mediated by cell cycle arrest at the G2/M phase, accompanied by inhibition of ornithine decarboxylase (ODC), the limiting enzyme of polyamine synthesis, and followed by induction of apoptosis.