Development of Fluorescent Isocoumarin-Fused Oxacyclononyne - 1,2,3-Triazole Pairs

Fluorescent isocoumarin-fused cycloalkynes, which are reactive in SPAAC and give fluorescent triazoles regardless of the azide nature, have been developed. The key structural feature that converts the non-fluorescent cycloalkyne/triazole pair to its fluorescent counterpart is the pi-acceptor group (COOMe, CN) at the C6 position of the isocoumarin ring. The design of the fluorescent cycloalkyne/triazole pairs is based on the theoretical study of the S1 state deactivation mechanism of the non-fluorescent isocoumarin-fused cycloalkyne IC9O using multi-configurational ab initio and DFT methodologies. The calculations revealed that deactivation proceeds through the electrocyclic ring opening of the α-pyrone cycle and is accompanied by a redistribution of electron density in the fused benzene ring. We proposed that the S1 excited state deactivation barrier could be increased by introducing a pi-acceptor group into a position that is in direct conjugation with the formed C=O group and has a reduced electron density in the transition state. As a proof of concept, we designed and synthesized two fluorescent isocoumarin-fused cycloalkynes IC9O-COOMe and IC9O-CN bearing pi-acceptors at the C6 position. The importance of the nature of a pi-acceptor group was shown by the example of much less fluorescent CF3 -substituted cycloalkyne IC9O-CF3 .

4,5,6,7-Tetrahydroindol-4-Ones as a Valuable Starting Point for the Synthesis of Polyheterocyclic Structures

This review focuses on the synthesis of polyheterocyclic structures with a variety of medicinal and optoelectronic applications, starting from readily available 4,5,6,7-tetrahydroindol-4-one analogs. First, routes toward the 4,5,6,7-tetrahydroindol-4-one starting materials are summarized, followed by synthetic pathways towards polyheterocyclic structures which are categorized based on the size and attachment point of the newly formed (hetero)cyclic ring.

A New Coumarin-Acridone Compound as a Fluorescence Probe for Fe3+ and Its Application in Living Cells and Zebrafish

A new coumarin-acridone fluorescent probe S was designed and synthesized, and the structure was confirmed with ¹H/¹³C NMR spectrometry, single-crystal X-ray diffraction, and high-resolution mass spectrometry. This probe has high sensitivity and selectivity for Fe³⁺ over other testing metal ions at 420 or 436 nm in acetonitrile-MOPS (3-Morpholinopropanesulfonic Acid) buffer solution (20.0 μM, pH = 6.9, 8:2 (v/v)). Under physiological conditions, the probe displayed satisfying time stability with a detection limit of 1.77 µM. In addition, probe S was successfully used to detect intracellular iron changes through a fluorescence-off mode, and the imaging results of cells and zebrafish confirmed their low cytotoxicity and satisfactory cell membrane permeability, as well as their potential biological applications.

Mekheimer R, M. Hayallah A, A. Abo Elsoud F, U. Sadek K. Recent Advances in the Utility of Glycerol as a Benign and Biodegradable Medium in Heterocyclic Synthesis

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Glycerol is a non-toxic, recyclable and biodegradable organic waste produced as a byproduct in the production of biodiesel fuel. Currently, glycerol is considered a green solvent and catalyst for a large variety of applications. This work discusses the significance of glycerol for heterocyclic synthesis. All the reported studies consider glycerol as an efficient and sustainable benign medium.

Copper-catalyzed one-pot reactions of acetyl chloride, o-halobenzoic acids and Wittig reagents toward 3-methyl isocoumarin synthesis

The synthesis of 3-methtyl isocoumarins is achieved via the copper-catalyzed one-pot reactions of Wittig reagents, acetyl chloride and o-iodobenzoic acids via tandem construction of CC, C–O and C–C bonds.

5-(N-Ethylcarbazol-3-yl)thiophene-2-carbaldehyde (ECTC): a novel fluorescent sensor for ferric ion

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Indium chloride catalyzed three-component reaction for the synthesis of 2-((oxoindolin-3-yl)-4,5,6,7-tetrahydro-1H-indol-1-yl)benzamides

In the presence of indium chloride as a Lewis acid catalyst, the three-component reaction afforded functionalized 2-((oxoindolin-3-yl)-4,5,6,7-tetrahydro-1H-indol-1-yl)benzamides in satisfactory yields.

Synthesis of a new class of pyrazole embedded spirocyclic scaffolds using magnetically separable Fe3O4@SiO2–SO3H nanoparticles as recyclable solid acid support

A green methodology for the synthesis of a new class of pyrazole embedded spirocyclic scaffolds has been developed using Fe₃O₄@SiO₂–SO₃H magnetic nanoparticles.

Synthesis of biologically important, fluorescence active 5-hydroxy benzo[g]indoles through four-component domino condensations and their fluorescence “Turn-off” sensing of Fe(iii) ions

The efficiently synthesized fluorescence active 5-hydroxy benzo[g]indoles show excellent fluorescence "Turn-off" sensing of Fe³⁺ ions.

A turn-on fluorescent pyrene-based chemosensor for Cu(ii) with live cell application

A pyrene-based fluorescent sensor (PHP) was synthesized for Cu(ii) detection.