Electrochemical Oxidative Carbonylation of NH-Sulfoximines

Electrifying Redox-Neutral Palladium-Catalyzed Carbonylations: Multielectron Transfer as a Catalyst Driving Force

Palladium-catalyzed bond-forming reactions such as carbonylations offer an efficient and versatile avenue to access products from often feedstock reagents. However, the use of catalysts also comes with a cost, as their need to be regenerated after each product-forming cycle requires balancing thermal operations. The latter can lead to high barriers even with catalysts as well as restrict their application to many products. We introduce herein an alternative approach to palladium catalyst design, where instead electrochemical potential can drive catalysis by continual two-electron cycling of the metal oxidation state. The power behind these redox steps offers a route to carry out carbonylation reactions, including the catalytic synthesis of high-energy aroyl halide electrophiles, at unprecedentedly mild ambient temperature and pressure. More generally, analysis suggests this catalyst functions by a distinct multi-electron exchange pathway, where two-electron reduction enables oxidative addition and two-electron oxidation drives product elimination. The combination creates a unique platform where both these reverse operations are favored in the same system and with electrochemical potential energy as the only added energy source.

Pyrolytic Carbon: An Inexpensive, Robust, and Versatile Electrode for Synthetic Organic Electrochemistry

Synthetic organic electrochemistry is recognized as one of the most sustainable forms of redox chemistry that can enable a wide variety of useful transformations. In this study, readily prepared pyrolytic carbon electrodes are explored in several powerful rAP transformations as well as C-C and C-N bond forming reactions. Pyrolytic carbon provides an alternative to classic amorphous carbon-based materials that are either expensive or ill-suited to large-scale flow reactions.

Electrochemical Halogenation of Naphthoquinones: A Modular and Sustainable Strategy Towards Trypanocidal Compounds

An eco-friendly electrochemical halogenation of 2-amino-1,4-naphthoquinones has been developed. The new mild and energy efficient methodology comprises sustainable features like oxidant free and double role of the halogen source as electrolyte, originating twenty-six amino-halogenated naphthoquinoidal derivatives in good yields under mild conditions. This novel methodology permitted access to new potent trypanocidal prototypes, where six compounds were more active than benznidazole, the current market drug used in the treatment of Chagas Disease.

Electrochemical NH-Sulfoximidation with α-Keto Acids

An electrochemical N-acylation of sulfoximine has been achieved via the coupling of α-keto acids and NH-sulfoximines. This process involves the sequential cleavage of C-C bond followed by C(sp2)-N bond formation, with the liberation of H2 and CO2 as the by-products. A library of N-aroylated sulfoximines is produced via the coupling of aroyl and sulfoximidoyl radicals by anodic oxidation under constant current electrolysis (CCE). The compatibility of the present protocol has been demonstrated by coupling of various bio-active compounds, such as NH-sulfoximine derived from (-)-borneol, L-menthol, D-glucose derivative, and some commercial drugs such as flurbiprofen, and ibuprofen. This late-stage functionalization highlights the importance of this sustainable protocol. Besides this, various control experiments and detection of H2 evolution have been performed to support the proposed mechanism.

Electrochemical oxidative thioetherification of aldehyde hydrazones with thiophenols

An electrochemically promoted oxidative dehydrogenation cross-coupling reaction between aldehyde hydrazones and thiophenols is demonstrated for the first time, which resulted in a variety of (Z)-thioetherified products in moderate to excellent yields. This strategy can be carried out under an air atmosphere, featuring scalability and excellent stereoselectivity. In addition, the transformation efficiently produces readily recyclable disulfide as a by-product with high yields, which significantly reduces the environmental pollution caused by thioetherification.

Electrochemically Enable N-Sulfenylation/Phosphinylation of Sulfoximines via Oxidative Dehydrocoupling Reaction

An electrochemical oxidative cross-coupling strategy for the synthesis of N-sulfenylsulfoximines from sulfoximines and thiols was accomplished, giving diverse N-sulfenylsulfoximines in moderate to good yields. Moreover, this strategy can be extended to construct the N-P bond of N-phosphinylated sulfoximines. With electrons as reagents, the oxidative dehydrogenation cross-coupling reaction proceeds smoothly in the absence of traditional redox reagents.