Enantioselective organocatalytic Friedel-Crafts reaction of electron-rich phenols and isatins by Takemoto's thiourea catalyst

Takemoto's catalysts were used to organocatalyze the enantioselective Friedel-Crafts reaction with different electron-rich phenols and substituted isatins. The resulting 3-aryl-3-hydroxyl-2-oxindoles were obtained in good yields (85-96%) with up to 99% ee. The substrate scope was broadened with this methodology compared to reported examples catalyzed by cinchonidine thiourea.

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.

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.

β-Lactams as promising anticancer agents: Molecular hybrids, structure activity relationships and potential targets

β-Lactam, commonly referred as azetidin-2-one, is a multifunctional building block for synthesizing β-amino ketones, γ-amino alcohols, and other compounds. Besides its well known antibiotic activity, this ring system exhibits a wide range of activities, attracting the attention of researchers. However, the structurally diverse β-lactam analogues as anticancer agents and their different molecular targets are poorly discussed. The purpose of this review is 3-fold: (1) to explore the molecular hybridization approach to design β-lactams hybrids as anticancer agents; (2) the structure activity relationship of the most active anticancer β-lactams and (3) to summarize their antitumor mechanisms.

Biosynthetic Functional Gene Analysis of Bis-Indole Metabolites from 25D7, a Clone Derived from a Deep-Sea Sediment Metagenomic Library

This work investigated the metabolites and their biosynthetic functional hydroxylase genes of the deep-sea sediment metagenomic clone 25D7. 5-Bromoindole was added to the 25D7 clone derived Escherichia coli fermentation broth. The new-generated metabolites and their biosynthetic byproducts were located through LC-MS, in which the isotope peaks of brominated products emerged. Two new brominated bis-indole metabolites, 5-bromometagenediindole B (1), and 5-bromometagenediindole C (2) were separated under the guidance of LC-MS. Their structures were elucidated on the basis of 1D and 2D NMR spectra (COSY, HSQC, and HMBC). The biosynthetic functional genes of the two new compounds were revealed through LC-MS and transposon mutagenesis analysis. 5-Bromometagenediindole B (1) also demonstrated moderately cytotoxic activity against MCF7, B16, CNE2, Bel7402, and HT1080 tumor cell lines in vitro.

Construction of highly enantioselective spiro-oxindole derivatives with fused chromene via organocascade catalysis

A first highly enantioselective addition of naphthols and sesamol to indolylidene cyanoacetate derived from isatins was carried out in the presence of bi-functional quinine thiourea as organocatalyst.

Strategies for the asymmetric functionalization of indoles: an update

During the past four years, the research of new synthetic methodologies for the rapid construction of enantiomerically pure substituted indole has had a fruitful and important growth.

Maleimide as an efficient nucleophilic partner in the aza-Morita–Baylis–Hillman reaction: synthesis of chiral 3-substituted-3-aminooxindoles

A highly enantioselective β-isocupreidine catalyzed aza-Morita–Baylis–Hillman reaction of maleimides with isatin derived ketimines provides 3-substituted-3-aminooxindoles with enantiomeric excess upto 99%.

Highly chemoselective synthesis of dimeric 2-oxindoles with a C-3/C-5′ linkage via Friedel–Crafts alkylations of 2-oxindoles with 3-hydroxy-2-oxindoles

An expeditious approach to a variety of dimeric 2-oxindoles with a C-3/C-5′ linkage sharing an all-carbon quaternary center at the pseudobenzylic position has been developed via Lewis acid-catalyzed F–C alkylations.

Indole-based alkaloids from deep-sea bacterium Shewanella piezotolerans with antitumor activities

Chromatographic separation of a crude extract obtained from a fermentation broth of a chemically unknown bacterium Shewanella piezotolerans WP3 collected in deep-sea yielded three new indole alkaloids namely shewanellines A (1a), B (1b) and C (2), together with 12 known indole alkaloids. The structures were unambiguously elucidated on the basis of 1D and 2D NMR ((1)H, (13)C, COSY, HMBC, HSQC and NOESY) in association with MS and CD data. Compounds 1-4, 7, 9 and 11-14 were selected for the evaluation of their cytotoxic activities against human tumor cell lines HL-60 and BEL-7402, whereas compounds 2, 4 and 9 exhibited significant inhibition toward HL-60.

Iron-catalyzed C(sp3)–H functionalization of methyl azaarenes: a green approach to azaarene-substituted α- or β-hydroxy carboxylic derivatives and 2-alkenylazaarenes

An iron-catalyzed C(sp³)–H functionalization of methyl azaarenes with carbonyls to access the title compounds have been described.

Cinchonidine thiourea catalyzed asymmetric addition of phenols to oxindole derivatives

A highly enantioselective Friedel–Crafts reaction of phenols with isatin derivatives catalyzed by Cinchona-derived thiourea provides biologically important 3-aryl-3-hydroxy-2-oxindoles in good to excellent yield with enantioselectivity up to 92% ee.

Organocatalytic enantioselective aza-Henry reaction of ketimines derived from isatins: access to optically active 3-amino-2-oxindoles

An organocatalytic asymmetric aza-Henry reaction of ketimines derived from isatins with nitroalkanes has been achieved using Cinchona alkaloid organocatalysts.