Iodine-Catalyzed Selective Synthesis of 2-SulfanylphenolsviaOxidative Aromatization of Cyclohexanones and Disulfides

Aminoselenation and Dehydroaromatization of Cyclohexanones with Anilines and Diselenides

A three-component cascade reaction involving cyclohexanones, anilines, and diaryl diselenides under metal-free conditions is reported. The ortho-selenation of cyclohexanones with diaryl diselenides, followed by sequential dehydroaromatization with anilines, enables the preparation of a variety of o-selanyl anilines in moderate to excellent yields. This innovative transformation is notable for its excellent tolerance of functional groups and is suitable for the late-stage modification of complex pharmaceuticals.

Carbocation Mechanism Revelation of Molecular Iodine-Mediated Dehydrogenative Aromatization of Substituted Cyclic Ketones to Phenols

Dehydrogenative aromatization (DA) of cyclic ketones is central to the development of functionalized aromatic precursors and hydrogen transfer-related technologies. Traditional DA strategies require precious metals with oxidants and are typically performed at high temperatures (100-150 °C) to overcome the high energy barrier of aliphatic C-H bond activation. Recently, a mild alternative approach based on I2 has been proposed to realize DA on substituted unsaturated cyclic ketones under ambient conditions. However, depending on the solvent, the product selectivity may vary between phenol ether and phenol, and the reaction mechanisms remain unclear. Herein, based on time-resolved proton nuclear magnetic resonance, DFT calculation, and mass spectrometric analyses, we established a unified mechanism to account for the product distribution. Through substrate scope and desorption electrospray ionization-mass spectrometry, we discovered the formation of a carbocation, which has been overlooked in previous studies. An expanded substrate scope study coupled with spectroscopic observation provided strong evidence to elucidate the formation mechanism and the location of the carbocation. With a renewed understanding of the mechanism, we achieved a phenolic product yield of 17-96% while controlling the selectivity. Moreover, some reactants could undergo DA in H2O, achieving 95-96% yield at below water-boiling temperature.

Dehydroaromatization of Indolines and Cyclohexanones with Thiol Access to Aryl Sulfides under Basic Conditions

Aryl sulfides are common and ubiquitous motifs in natural products and pharmaceuticals. Presented herein is the first example of the synthesis of diaryl sulfide derivatives via dehydroaromatization under simple basic conditions. Dehydroaromatization reactions between indolines or cyclohexanones with aryl thiols are performed in an environmentally benign manner by the use of air (molecular oxygen) as the oxidant, with producing water as the only byproduct. The methodology provides a simple and practical route to diaryl sulfides with wide functional groups in good to excellent yields. Preliminary mechanistic studies suggest that a radical process is involved in the transformation.

Recent advances in the transition metal-free oxidative dehydrogenative aromatization of cyclohexanones

Cyclohexanone is a simple and widely available raw material that can be obtained from lignin biomass, highlighting its renewable and sustainable features. Cyclohexanone, as an important synthon in organic chemistry, has been demonstrated to be viable for constructing functionalized arenes and benzoheteroarenes, with recent extensive development on transition metal-free oxidative dehydrogenative aromatization. This review focuses on recent research progress on the transition metal-free derivation of cyclohexanones via oxidative dehydrogenative aromatization.

Tritylium assisted iodine catalysis for the synthesis of unsymmetrical triarylmethanes

The combined Lewis acid catalytic system, generated from molecular iodine and tritylium tetrafluoroborate effectively catalyzed the Friedel-Crafts (FC) arylation of diarylmethyl sulfides providing an efficient access to various unsymmetrical triarylmethanes. The addition of tritylium and iodine created a more active catalytic system to promote the cleavage of sulfidic C-S bonds.

One-Step Synthesis of Furan Rings from α-Isopropylidene Ketones Mediated by Iodine/DMSO: An Approach to Potent Bioactive Terpenes

The system I₂/dimethyl sulfoxide mediates the one-step transformation of α-isopropylidene ketones into furan rings following a biomimetic approach. This methodology has been used for the synthesis of terpene furans such as mintfurane, curzerene, atractylon, and isoatractylon, all of them possessing interesting biological activities. The synthesis of linderazulene directly from 4,5-epoxygermacrone via a cascade reaction shows the potential of this protocol. Additionally, this compound proved to show significant ixodicidal activity.

Molecular iodine-mediated synthesis of thiocarbamates from thiols, isocyanides and water under metal-free conditions

A simple and practical molecular iodine-mediated method for the efficient construction of thiocarbamates from isocyanides, thiols and water under metal-free and mild conditions has been developed. A variety of thiocarbamates were easily synthesized through this methodology, which has the advantages of simple operation, eco-friendly conditions, good functional group tolerance, and readily accessible raw materials.

Synthesis of disulfides tethered pyrroles from β-ketothioamides via a bicyclization/ring-opening/oxidative coupling reaction

A DABCO-promoted three-component reaction of β-ketothioamides, arylglyoxals and 2-cyanoacetate to construct disulfides tethered pyrroles has been developed.

Regioselective thiolation of electron rich arenes and heterocycles in recyclable catalytic media

A convenient and novel approach has been developed for the synthesis of unsymmetrical diaryl sulfides by the reaction of sulfonyl hydrazides with phenols, aromatic amines and heterocycles using a [Bmim][Br] ionic liquid through C–S bonds formation.

Iodine, a Mild Reagent for the Aromatization of Terpenoids

Efficient procedures based on the use of iodine for the aromatization of a series of terpenoids possessing diene and homoallylic or allylic alcohol functionalities are described. Different examples are reported as a proof-of-concept study. Furthermore, iodine also proved to mediate the dehydrogenation of testosterone.

Palladium-catalyzed benzothieno[2,3-b]indole formation via dehydrative–dehydrogenative double C–H sulfuration using sulfur powder, indoles and cyclohexanones

An efficient procedure for benzothieno[2,3-b]indole formation via double C–H sulfuration using sulfur powder is described.

Iodine-catalyzed C–H/S–H oxidative coupling: from 1,3-diketones and thiophenols to β-dicarbonyl thioethers

A novel I₂-catalyzed Csp³-H/S–H oxidative coupling between alkyl 1,3-diketones and thiophenols to form β-carbonyl thioethers was demonstrated.

Palladium-catalyzed thiolation of alkanes and ethers with arylsulfonyl hydrazides

A new method for the preparation of alkyl aryl sulfides through direct oxidative thiolation of alkanes or ethers with arylsulfonyl hydrazides using DTBP as an oxidant catalyzed by Pd(OAc)₂ has been reported. The C–H bonds in various alkanes or ethers were successfully converted into C–S bonds with moderate to good yields.