Electrochemical C–H phosphorylation of arenes in continuous flow suitable for late-stage functionalization

The activation of C–H bond, and its direct one-step functionalization, is one of the key synthetic methodologies that provides direct access to a variety of practically significant compounds. Particular attention is focused on modifications obtained at the final stages of the synthesis of complicated molecules, which requires high tolerance to the presence of existing functional groups. Phosphorus is an indispensable element of life, and phosphorus chemistry is now experiencing a renaissance due to new emerging applications in medicinal chemistry, materials chemistry (polymers, flame retardants, organic electronics, and photonics), agricultural chemistry (herbicides, insecticides), catalysis (ligands) and other important areas of science and technology. In this regard, the search for new, more selective, low-waste synthetic routes become relevant. In this context, electrosynthesis has proven to be an eco-efficient and convenient approach in many respects, where the reagents are replaced by electrodes, where the reactants are replaced by electrodes, and the applied potential the applied potential determines their “oxidizing or reducing ability”. An electrochemical approach to such processes is being developed rapidly and demonstrates some advantages over traditional classical methods of C-H phosphorylation. The main reasons for success are the exclusion of excess reagents from the reaction system: such as oxidants, reducing agents, and sometimes metal and/or other improvers, which challenge isolation, increase the wastes and reduce the yield due to frequent incompatibility with these functional groups. Ideal conditions include electron as a reactant (regulated by applied potential) and the by-products as hydrogen or hydrocarbon. The review summarizes and analyzes the achievements of electrochemical methods for the preparation of various phosphorus derivatives with carbon-phosphorus bonds, and collects data on the redox properties of the most commonly used phosphorus precursors. Electrochemically induced reactions both with and without catalyst metals, where competitive oxidation of precursors leads to either the activation of C-H bond or to the generation of phosphorus-centered radicals (radical cations) or metal high oxidation states will be examined. The review focuses on publications from the past 5 years.

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“… Reaction scope, isolated yields. The ratio of regio-isomers is given according to the NMR data of the reactor feed ( Long et al, 2021 ). …”

Section: Electrochemical Metal-free C–h Phosphorylation Of Aromatic H...mentioning

confidence: 99%

“…or (RO) 2 P(O)H (2 eqv.) and electrolysis in a flow cell ( Long et al, 2021 ). Conditions of electrosynthesis in a continuous flow have proved favourable for the conversion of electron-rich and electron-deficient arenes into various arylphosphonates with high yields.…”

Section: Electrochemical Metal-free C–h Phosphorylation Of Aromatic H...mentioning

confidence: 99%

Recent advances in electrochemical C—H phosphorylation

et al. 2022

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“…In recent years, organic electrochemical synthesis has become an attractive approach in the field of organic synthesis because of its environmentally benign, sustainable, and practical nature [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Recently, several electrochemically induced radical functionalizations of alkynes have been reported [ 43 , 44 , 45 , 46 ].…”

Section: Introductionmentioning

confidence: 99%

Direct Electrooxidative Selenylation/Cyclization of Alkynes: Access to Functionalized Benzo[b]furans

Balati

Lin²,

Zheng³

et al. 2022

Molecules

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A mild, practical, metal and oxidant-free methodology for the synthesis of various C-3 selenylated benzo[b]furan derivatives was developed through the intramolecular cyclization of alkynes promoted with diselenides via electrooxidation. A wide range of selenium-substituted benzo[b]furan derivatives were obtained in good to excellent yields with high regioselectivity under constant current in an undivided cell equipped with carbon and platinum plates as the anode and cathode, respectively. Moreover, the convergent approach exhibited good functional group tolerance and could be easily scaled up with good efficiency, providing rapid access to a diverse range of selenylated benzo[b]furans derivatives from simple, readily available starting materials.

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“…When we added P(OEt) 3 to the coupling reaction between 1b and 2a , compounds 8 and 9 were detected by HR-MS (Scheme 3a). 17 In addition, a trace mount of compound 10 was also isolated during the preparation process of compound 3b (Scheme 3b). 18 Thus, the indole and benzofuran radical cation are possibly involved under this electrochemical condition.…”

mentioning

confidence: 99%