Electrochemical generation of phenothiazin-5-ium. A sustainable strategy for the synthesis of new bis(phenylsulfonyl)-10H-phenothiazine derivatives

In this work, the electrochemical generation of phenothiazin-5-ium (PTZox) from the direct oxidation of phenothiazine (PTZ) in a water/acetonitrile mixture using a commercial carbon anode and conventional stainless steel cathode is reported. PTZox is a reactive intermediate with high potential synthetic applications, which is used in this paper for the synthesis of new phenothiazine derivatives. In this work a novel and simple electrochemical methodology for the synthesis of some bis(phenylsulfonyl)-10H-phenothiazine derivatives was established. In this paper, a mechanism for PTZ oxidation in the presence of arylsulfinic acids has been proposed based on the results obtained from voltammetric and coulometric experiments as well as spectroscopic data of the products. These syntheses are performed in a simple cell by applying constant current under mild conditions and at room temperature with high atom economy.

Heterogeneous copper-catalyzed synthesis of diaryl sulfones

A carbon-supported copper nanoparticle (Cu-NP) with high catalytic activity for the synthesis of diaryl sulfones is reported. For the first time, this Cu-NP is proved to be able to effectively promote the reaction of arylboronic acids and arylsulfonyl hydrazides to generate diaryl sulfones at room temperature. The reaction shows excellent substrate universality, and substrates with different substituents can undergo the reaction smoothly, leading to the desired products in good yields. The Cu-NP is found to be made of low valence Cu based on XRD. Hence, the reaction catalyzed by the Cu-NP is believed to involve a Cu-mediated organometallic cycle.

Nanosized CdS as a Reusable Photocatalyst: The Study of Different Reaction Pathways between Tertiary Amines and Aryl Sulfonyl Chlorides through Visible-Light-Induced N-Dealkylation and C-H Activation Processes

It has been found that the final products of the reaction of sulfonyl chlorides and tertiary amines in the presence of cadmium sulfide nanoparticles under visible light irradiation are highly dependent on the applied reaction conditions. Interestingly, with the change of a reaction condition, different pathways were conducted (visible-light-induced N-dealkylation or sp³ and sp² C-H activation) that lead to different products such as secondary amines and various sulfonyl compounds. Remarkably, all of these reactions were performed under visible light irradiation and an air atmosphere without any additive or oxidant in benign solvents or under solvent-free conditions. During this study, the CdS nanoparticles as affordable, heterogeneous, and recyclable photocatalysts were designed, successfully synthesized, and fully characterized and applied for these protocols. During these studies, intermediates resulting from the oxidation of tertiary amines are trapped during the photoinduced electron transfer (PET) process. The reaction was carried out efficiently with a variety of substrates to give the corresponding products at relatively short times in good to excellent yields in parallel with the use of the visible light irradiation as a renewable energy source. Most of these processes are novel or are superior in terms of cost-effectiveness, safety, and simplicity to published reports.

Electrochemical study of 4-chloroaniline in a water/acetonitrile mixture. A new method for the synthesis of 4-chloro-2-(phenylsulfonyl)aniline and N-(4-chlorophenyl)benzenesulfonamide

The electrochemical oxidation of 4-chloroaniline as a model compound in a water/acetonitrile mixture was investigated by cyclic voltammetry and differential pulse voltammetry. It was established that one-electron oxidation of 4-chloroaniline followed by disproportionation reaction affords unstable (4-iminocyclohexa-2,5-dien-1-ylidene)chloronium. In water/acetonitrile mixtures and in the absence of nucleophiles, the most likely reaction on produced chloronium is hydrolysis and p-quinoneimine formation. The electrochemical oxidation of 4-chloroaniline in the presence of arylsulfinic acids was also investigated in a water/acetonitrile mixture at a glassy carbon electrode. It was established that under these conditions, the anodically generated chloronium reacts with benzenesulfinic acid to produce the corresponding diaryl sulfone and N-phenylbenzenesulfonamide derivatives. In addition, Gaussian 09W was applied for prediction of the possible product by the calculation of natural charge, LUMO orbital energies and thermodynamic stability of intermediates and products.

Electrochemical oxidation pathway of p-chloroaniline (PCA) in the presence of benzenesulfinic acid (BSA).

Organic photoredox catalysis enabled cross-coupling of arenediazonium and sulfinate salts: synthesis of (un)symmetrical diaryl/alkyl aryl sulfones

Transition-metal- and oxidant/reductant-free visible-light-mediated synthesis of (un)symmetrical diaryl/alkyl aryl sulfones from aryl diazonium and sulfinate salts employing eosin Y as an organo-photoredox catalyst is reported.