“On water” expedient synthesis of 3-indolyl-3-hydroxy oxindole derivatives and their anticancer activity in vitro

Visible-Light-Mediated Generation of Acyl Radicals from Triazine Esters

Acyl radicals are significant synthetic active species in organic synthesis. However, their generation via green and compatible methods remains challenging. Herein, we report an unprecedented visible-light-mediated approach for generating aryl acyl radicals from readily available triazine esters. This protocol with mild and redox-neutral conditions affords a diverse array of oxindoles attached to alcohol groups in a single operation. The recycling of leaving groups and a range of visible-light-mediated reactions using triazine ester as an acyl radical precursor demonstrate the synthetic potential of this methodology.

A new reversible transformation of oxindolylidene derivatives of imidazothiazolotriazine into 3-[(imidazotriazin-3-yl)thio]-2-oxoquinoline-4-carboxylates

A simple method for the synthesis of water-soluble potassium 3-[(imidazotriazin-3-yl)thio]-2-oxoquinoline-4-carboxylates was developed based on a new reversible transformation of oxindolylidene derivatives of imidazothiazolotriazine that results from their treatment with potassium hydroxide. The antiproliferative activity of the synthesized compounds was evaluated against 58 cell lines and compared with oxindolylidene derivatives of imidazothiazolotriazine. Quinoline derivatives 3 demonstrated high activity with average GI₅₀ values of <10 μM which are comparable or higher than those of the oxindolylidene imidazothiazolotriazines. Compound 3a, with a pent-3-yl substituent at the nitrogen atom of the quinoline fragment, possessed the highest antiproliferative activity with an average GI₅₀ value of 1.71 μM. The GI₅₀ values of compound 3a against 52 of the 58 cell lines were <1 μM; against the remaining 6 of the 58 cell lines, they were in the range 1.21-39.2 μM.

Multicomponent Assembly of Complex Oxindoles by Enantioselective Cooperative Catalysis

Chiral oxindoles are important chemical scaffolds found in many natural products, and their enantioselective synthesis thus attracts considerable attention. Highly diastereo- and enantioselective synthetic methods for constructing C3 quaternary oxindoles have been well-developed. However, the efficient synthesis of chiral 3-substituted tertiary oxindoles has been rarely reported due to the ease of racemization of the tertiary stereocenter via enolization. Therefore, we herein report on the multicomponent assembly (from N-aryl diazoamides, aldehydes, and enamines/indoles) of complex oxindoles by enantioselective cooperative catalysis. These reactions proceed under mild conditions and show broad substrate scope, affording the desired coupling products (>90 examples) with good to excellent stereocontrol. Additionally, this research also demonstrates the synthetic potential of this annulation by constructing the 6,6,5-tricyclic lactone core structure of Speradine A.

A Mini Review on Isatin, an Anticancer Scaffold with Potential Activities against Neglected Tropical Diseases (NTDs)

Isatin, chemically an indole-1H-2,3-dione, is recognised as one of the most attractive therapeutic fragments in drug design and development. The template has turned out to be exceptionally useful for developing new anticancer scaffolds, as evidenced by the increasing number of isatin-based molecules which are either in clinical use or in trials. Apart from its promising antiproliferative properties, isatin has shown potential in treating Neglected Tropical Diseases (NTDs) not only as a parent core, but also by attenuating the activities of various pharmacophores. The objective of this mini-review is to keep readers up to date on the latest developments in the biological potential of isatin-based scaffolds, targeting cancer and NTDs such as tuberculosis, malaria, and microbial infections.

Design, synthesis and in vitro evaluation of the hybrids of oxindolylidene and imidazothiazolotriazine as efficient antiproliferative agents

1,3-Diethyl-6-oxindolylidenetetrahydroimidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazine-2,7-dione with 2-propyl substituent at the nitrogen atom of oxindole fragment (1d) was identified previously as a lead compound in an antiproliferative agent discovery effort based on oxindolylidene derivatives of...

Chiral Heterogeneous Scandium Lewis Acid Catalysts for Continuous-Flow Enantioselective Friedel-Crafts Carbon-Carbon Bond-Forming Reactions

While continuous-flow reactions with chiral heterogeneous catalysts provide a highly efficient method to synthesize optically active compounds, chiral heterogeneous Lewis acid catalysis has been less extensively explored. We have developed the first example of chiral heterogeneous Sc catalysts, which demonstrated excellent activity and selectivity for continuous-flow enantioselective Friedel-Crafts reactions of isatins with indoles. Noncovalent interactions between chiral Sc complexes and heteropoly acid-anchored amine-functionalized SiO₂ as support were utilized for the synthesis. The heteropoly acid was found to be crucial for the preparation, activity, and selectivity of the catalysts. The chiral ligand could be easily tuned without chemical modification and the continuous-flow synthesis of a biologically active compound was achieved.

Mandelic Acid: An Efficient Organo-catalyst for the Synthesis of 3-substituted-3- Hydroxy-indolin-2-ones and Related Derivatives in Aqueous Ethanol at Room Temperature

Background:

Indoles and various indolyl derivatives are very common in naturally occurring biologically active compounds. Many methods are being developed for the synthesis of various bioactive indole derivatives.

Objective:

Synthesis of biologically promising structurally diverse indole derivatives under mild and environmentally benign conditions.

Methods:

Synthesis of 3-hydroxy-3-(5-(trifluoromethoxy)-1H-indol-3-yl)indolin-2-one was achieved by the reaction of an equimolar mixture of isatin and 3-(trifluoromethoxy)-1H-indol using 20 mol% of mandelic acid as catalyst in aqueous ethanol at room temperature. Under the same optimized reaction conditions, synthesis of 3-(3-hydroxy-2-oxoindolin-3-yl)chroman-2,4-diones was accomplished via the reactions of substituted isatins and 4-hydroxycoumarin. On the other hand, 2-hydroxy-2-(indol-3-yl)- indene-1,3-diones and 10-hydroxy-10-(5-methoxy-1H-indol-3- yl)phenanthren-9(10H)-one were synthesized from the reactions of indoles and ninhydrin or 9,10-phenanthrenequinone respectively using the same 20 mol% of mandelic acid as an efficient organo-catalyst in aqueous ethanol at room temperature.

Results:

Mild, safe and clean reaction profiles, energy efficiency, high atom-economy, use of naturally occurring non-toxic organo-catalyst, easy isolation procedure by avoiding column chromatographic purification and gram scale production are some the major advantages of this developed protocol.

Conclusion:

A simple, straightforward and eco-friendly protocol has been developed for the efficient synthesis of biologically promising novel 3-hydroxy-3-(5-(trifluoromethoxy)-1H-indol- 3-yl)indolin-2- one, 3-(3-hydroxy-2-oxoindolin-3-yl)chroman-2,4-diones, 2-hydroxy-2-(indol-3- yl)-indene-1,3-diones and 10-hydroxy-10-(5-methoxy-1H-indol-3-yl)phenanthren-9(10H)-one using a catalytic amount of mandelic acid in aqueous ethanol at room temperature.

Vibrational, spectroscopic, chemical reactivity, molecular docking and in vitro anticancer activity studies against A549 lung cancer cell lines of 5-Bromo-indole-3-carboxaldehyde

Spectroscopic investigations are performed for 5-Bromo-1H-indole-carboxaldehyde by using experimental (FT-IR, FT-Raman) and theoretical (DFT) calculations. Vibrational assignments of the fundamental modes were assigned on the basis of Potential energy distribution (PED) calculations. Electron Localization Function (ELF) and Local Orbital Localizer (LOL) studies were performed to visualize the electron delocalization in the molecule. Frontier molecular orbitals (FMOs) and related molecular properties were computed. The electron-hole distribution of the molecule was also computed using Multiwfn 3.3.9 software to predict the charge transfer within the molecule. The total and partial density of states (TDOS and PDOS) and also the overlap population density of states (OPDOS) spectra were simulated. UV-Vis spectrum of the compound was also recorded. The reactive sites of the compound were studied from the MEP and Fukui function analysis. The charge delocalization and stability of the title molecule were investigated using natural bond orbital (NBO) analysis. The lung cancer activity of the title compound against p53 tumor suppressor proteins was studied using molecular docking analysis. The in-vitro cytotoxic activity of the molecule against human pulmonary lung cancer cell lines (A549) was determined by MTT assay.

Brønsted-acid-catalyzed selective Friedel-Crafts monoalkylation of isatins with indolizines in water

The controlled mono-addition of indolizines to isatins under very mild conditions is described. The reaction occurs in water using diphenylphosphate as the catalyst, which is dramatically accelerated by surfactant addition. 3-Hydroxy-3-indolizinyl-2-oxindole scaffolds were synthesized in up to >99% yield. Notably, in organic solvents only bis-addition products were observed.

A One-Pot Divergent Sequence to Pyrazole and Quinoline Derivatives

The hydroxy-pyrazole and 3-hydroxy-oxindole motifs have been utilised in several pharma and agrochemical leads but are distinctly underrepresented in the scientific literature due to the limited routes of preparation. We have developed a one-pot procedure for their synthesis starting from simple isatins. The method employs cheap and easy-to-handle building blocks and allows easy isolation.

Domino Grignard Addition and Oxidation for the One-Pot Synthesis of C2-Quaternary 2-Hydroxyindoxyls

We herein delineate an unexplored reactivity of 3-hydroxyoxindoles toward Grignard addition enabling a rapid access to a broad range of unnatural C2-quaternary 2-hydroxyindoxyls in high yields. The reaction proceeds via a mechanistically intriguing one-pot 1,2-hydride shift followed by autoxidation pathway. The utility of this method is demonstrated by the synthesis of a new class of bis-indoxyl spirofuran derivatives.

Direct Csp3-H methylenation of 2-arylacetamides using DMF/Me2NH-BH3 as the methylene source

A direct Csp3-H methylenation of 2-arylacetamides using DMF/Me2NH-BH3 as the methylene source was developed. The formyl group of DMF delivered the carbon and one hydrogen atoms, and the Me2NH-BH3 donated the remaining one hydrogen atom. This protocol offers a new alternative to make useful 2-arylacrylamides from simple starting materials.

3-Hydroxy-3-((3-methyl-4-nitroisoxazol-5-yl)methyl)indolin-2-one as a versatile intermediate for retro-Henry and Friedel–Crafts alkylation reactions in aqueous medium

The first example of a retro-Henry type reaction is reported using 3-hydroxy-3-((3-methyl-4-nitroisoxazol-5-yl)methyl)indolin-2-ones which are prepared via catalyst-free Henry reaction of 3,5-dimethyl-4-nitroisoxazole and isatin.

Synthesis of enamino-2-oxindoles via conjugate addition between α-azido ketones and 3-alkenyl oxindoles: Cytotoxicity evaluation and apoptosis inducing studies

A facile method for the construction of double bond between 3-ylidene oxindoles and α-azido ketones has been successfully accomplished with a mild base. This method features azido reduction with concomitant double bond formation to provide the new class of bioactive enamino-2-oxindoles. These new compounds were screened for their in vitro cytotoxic potential on selected human cancer cell lines such as colon, lung, breast, and cervical cancer cells. Among them, representative compounds 3a, 3h, 3k, 3p, 3w and 3x showed notable cytotoxicity profile with IC₅₀ values ranging from 1.40 ± 0.10 to 28.7 ± 0.36 µM. Compound 3k displayed most potent cytotoxicity against lung cancer (NCI-H460) cells with an IC₅₀ value of 1.40 ± 0.10 µM. 3k also arrested the G2/M phase of the cell cycle and induced distinctive apoptotic features on lung cancer cells. The apoptosis induction is supported by various cellular assays such as AO/EB, DAPI, and DCFDA staining studies including clonogenic assay. Extent of apoptosis was also analyzed by Annexin binding and JC-1 staining. Moreover, this method is amenable for the generation of a library of new class of stable bioactive enamino-2-oxindoles.

The influence of substituents on the reactivity and cytotoxicity of imidazothiazolotriazinones

A series of tetrahydroimidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazine-2,7(1H, 6H)-diones were synthesized via the reaction of imidazotriazinethiones and bromoacetic acid followed by condensation with isatins. Amidine skeletal rearrangement of 3,3a,9,9a-tetrahydroimidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazine-2,7 (1H, 6H)-diones into 1,3a,4,9a-tetrahydroimidazo[4,5-e]thiazolo[2,3-c]-1,2,4-triazine-2,8 (3H, 7H)-diones under KOH treatment has been studied. The influence of substituents at positions 1,3,3a,6,9a of imidazothiazolotriazine on the ability to undergo rearrangement was analyzed based on experimental data and theoretical calculations. Both imidazothiazolo[3,2-b]triazines and their rearrangement products were evaluated for their cytotoxic activity against rhabdomyosarcoma, A549, HCT116 and MCF7 human cancer cell lines by MTT assay. Among the derivatives, 1,3-diethyl-6-[1-(2-propyl)-2-oxoindolin-3-ylidene]-3,3a,9,9a-tetrahydroimidazo [4,5-e]thiazolo[3,2-b]-1,2,4-triazine-2,7(1H, 6H)-dione 4i was found to have the highest antiproliferative activity toward the tested cell lines (4i: [Formula: see text], 2.29, 0.47 and [Formula: see text], respectively). The [Formula: see text] value of compound 4i against normal human embryonic kidney cells HEK293 was [Formula: see text], which appeared to be 6-41-fold higher than [Formula: see text] values of 4i against human cancer cells.

Organocatalytic Insertion of Isatins into Aryl Difluoronitromethyl Ketones

An organocatalytic method that achieves insertion of isatins into aryl difluoronitromethyl ketones under mild conditions is described. The reaction occurs in the presence of 20 mol % of DBU and with 100% atom economy. A series of isatin derived difluoronitromethyl substituted tertiary alcohol benzoates and naphthoates were prepared in 81-99% yield. The general synthetic usefulness of these 3-hydroxyoxindole derivatives is demonstrated with the selective reduction to fluorooximes.

Stereospecific diaza-Cope rearrangement as an efficient tool for the synthesis of DPEDA pyridine analogs and related C2-symmetric organocatalysts

Enantiomerically pure trans-1,2-di-(pyridinyl)ethylene-1,2-diamines were synthesized via a stereospecific diaza-Cope rearrangement and converted to prolinamide-based recyclable organocatalysts.

An efficient Friedel–Crafts alkylation for the synthesis of 3-indolyl-3-hydroxy oxindoles and unsymmetrical 3,3-diaryl oxindoles catalyzed by Dabco-based ionic liquids in water

An efficient, green and reusable catalytic system for controlled 3-indolylation of isatins.

5,5′-Bistriazoles as axially chiral, multidentate ligands: synthesis, configurational stability and catalytic application of their scandium(iii) complexes

The design and development of 5,5′-bistriazoles featuring aminomethyl substituents is discussed.

Embedding electron-deficient nitrogen atoms in polymer backbone towards high performance n-type polymer field-effect transistors

With sp2-nitrogen atoms embedded in an isatin unit, a donor-acceptor (D-A) conjugated polymer AzaBDOPV-2T was developed with a low LUMO level down to -4.37 eV. The lowered LUMO level as well as the conformation-locked planar backbone provide AzaBDOPV-2T with electron mobilities over 3.22 cm2 V-1 s-1 tested under ambient conditions, which is among the highest in n-type polymer field-effect transistors (FETs). Our results demonstrate that embedding electron-deficient sp2-nitrogen in conjugated backbones is an effective approach to develop n-type polymer semiconductors with high performance.

Oxindole: A chemical prism carrying plethora of therapeutic benefits

Oxindole has emerged as a valuable scaffold in medicinal chemistry possessing diverse range of pharmacological activities. Its value has further been increased by its natural occurrence as alkaloids in variety of plants. It was first extracted from the cat claw's plant Uncaria tomentosa found in the Amazon rainforest and other tropical areas of South and Central America. Traditionally as well as present emerging therapeutic potential of oxindole nucleus has captured the interest of medicinal chemists to synthesize novel oxindole derivatives. In the present review the authors have integrated its chemistry and synthetic strategies developed after 1945. Also the information of naturally occurring oxindole alkaloids has been incorporated. The detailed pharmacological activities including anti-cancer, anti-HIV, antidiabetic, antibacterial, antioxidant, kinase inhibitory, AChE inhibitory, anti-leishmanial, β3 adrenergic receptor agonistic, phosphatase inhibitory, analgesic, spermicidal, vasopressin antagonists, progesterone antagonists, neuroprotection, and NMDA blocker activities of oxindole derivatives alongwith their SAR has also been discussed in detail. Additionally, information regarding the oxindole derivatives in clinical trials has been incorporated. Thus, this review will provide insights for the synthetic as well as medicinal chemist for the designing and synthesis of novel oxindole derivatives with novel improved range of pharmacological implications.