I2-Cs2CO3 Mediated Intramolecular C2-Amination and Oxidative Rearrangement Cascade of C-3 Phenylthio Indoles: A Route to Synthesize Thiosulfonate-Embedded 2-Iminoindolin-3-ones.

An efficient, transition-metal-free protocol employing I2/Cs2CO3 for the synthesis of thiosulfonate containing 2-iminoindolin-3-ones motifs has been developed from C-3 phenylthio indoles. The reaction proceeded through intramolecular cyclization involving C-N bond formation, leading to the formation of indole-fused benzothiazines as a key intermediate. Remarkably, Cs2CO3 played a crucial role in the reaction as an oxygen source, enabling oxidative rearrangement with [1,4]-sulfonyl migration to furnish the final products with the formation of multiple functional groups such as C═O, C═N, and S-SO2.

Iodine-promoted sequential C(sp3)-H oxidation and cyclization of aryl methyl ketones with 2-(2-aminophenyl)quinazolin-4(3H)-ones.

An I2-promoted, metal-free protocol has been developed for the one-pot synthesis of 6-aroyl-5,6-dihydro-8H-quinazolino[4,3-b]quinazolin-8-ones from readily accessible substrates. This reaction involves the in situ sp3 C-H oxidation of aryl methyl ketones to phenylglyoxal, followed by imine formation and intramolecular nucleophilic addition, resulting in the formation of two new C-N bonds. Furthermore, the method is applicable to a wide range of aryl methyl ketones, including heterocycles and drug-derived substrates, yielding the desired products with yields ranging from 62% to 93%. Additionally, the practical utility of this approach was demonstrated through gram-scale synthesis.

I2-catalyzed tandem sp3 C-H oxidation and annulation of aryl methyl ketones with amidoximes for the synthesis of 5-aroyl-1,2,4-oxadiazoles.

A metal-free, iodine-catalyzed protocol has been developed for constructing biologically significant 5-aroyl 1,2,4-oxadiazole scaffolds using aryl methyl ketones and amidoximes. The strategy produces structurally diverse 5-aroyl 1,2,4-oxadiazoles in good to excellent yields, with a broad substrate scope that includes drug derived substrates. The reaction proceeds through iodine/DMSO-mediated oxidation of aryl methyl ketones, followed by imine formation and subsequent cyclization to yield the desired products. Additionally, this protocol has successfully produced the carbonyl analogs of ataluren and tioxazafen and has facilitated some intriguing late-stage transformations.

Synthesis of Di(thiophen-2-yl) Substituted Pyrene-Pyridine Conjugated Scaffold and DFT Insights: A Selective and Sensitive Colorimetric, and Ratiometric Fluorescent Sensor for Fe(III) Ions.

In this context, we used the multicomponent Chichibabin pyridine synthesis reaction to synthesize a novel di(thiophen-2-yl) substituted and pyrene-pyridine fluorescent molecular hybrid. The computational (DFT and TD-DFT) and experimental investigations were performed to understand the photophysical properties of the synthesized new structural scaffold. The synthesized ligand displays highly selective fluorescent sensing properties towards Fe3+ ions when compared to other competitive metal ions (Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Hg2+, Na+, Ni2+, Pb2+, Sr2+, Sn2+ and Zn2+). The photophysical properties studies reveal that the synthesized hybrid molecule has a binding constant of 2.30 × 103 M-1 with limit of detection (LOD) of 4.56 × 10-5 M (absorbance mode) and 5.84 × 10-5 M (emission mode) for Fe3+ ions. We believe that the synthesized pyrene-conjugated hybrid ligand can serve as a potential fluorescent chemosensor for the selective and specific detection of Fe3+ ions.

Iodine-Catalyzed Synthesis of Benzo-ß-carbolines through Desulfurative Cyclization of 2-(1H-Indol-3-ylsulfanyl)-phenylamines with Aryl Methyl Ketones.

A novel transition metal-free strategy for the synthesis of benzene-fused ß-carboline scaffolds has been developed. This protocol offers a rapid and direct pathway to access the benzene fused ß-carboline from 2-(1H-indol-3-ylsulfanyl)-phenylamines and aryl methyl ketones using an efficient catalytic system of I2/DMSO. The present mild protocol proceeds through the sequential reactions of Kornblum oxidation, Pictet-Spengler cyclization, and desulfurization to afford the desired products in excellent yields up to 99%. Moreover, this method has a wide range of substrate tolerance and is operationally simple and applicable in gram-scale synthesis.

Multicomponent Reaction Based Tolyl-substituted and Pyrene-Pyridine Conjugated Isomeric Ratiometric Fluorescent Probes: A Comparative Investigation of Photophysical and Hg(II)-Sensing Behaviors.

Herein, the synthesis of pyrene conjugated 2,6-di-ortho-tolylpyridine and 2,6-di-para-tolylpyridine structural isomers were achieved efficiently through multicomponent Chichibabin pyridine synthesis reaction. The DFT, TD-DFT and experimental investigations were carried out to investigate the photophysical behaviors of the synthesized novel pyrene-pyridine based isomeric probes. Our studies revealed that, due to the continuous conjugation of the pyrene, pyridine and tolyl moieties, the dihedral angles of the trisubstituents on the central pyridine moiety significantly influences the photophysical properties of the synthesized novel pyrene based fluorescent probes. Further, we have comparatively investigated the sensing behaviors of the synthesized tolyl-substituted isomeric ratiometric fluorescent probes with metal ions, our studies reveals that both the ortho and para tolyl ratiometric fluorescent probes have distinct photoemissive properties in selectively sensing of Hg2+ ions. Our studies indicates that, the para-tolyl substituted isomer displays more red-shift in wavelength of emission band compared to its ortho isomer analogue during ratiometric fluorescent specific detection of Hg2+ ions.