Scientists of the Zelinsky Institute have studied electrochemical cyclization under the action of hypervalent iodine compounds
Electric current is a powerful tool for carrying out various oxidative coupling processes, including the construction of C-N bonds and the synthesis of N-heterocyclic compounds. A promising direction in organic electrochemistry is reactions under the action of electrochemically generated hypervalent iodine compounds.
The process of intramolecular oxidative C-N-coupling of α,β-unsaturated hydrazones with the formation of substituted pyrazoles, catalyzed by hypervalent iodine compounds, was discovered at the Laboratory for the Study of Homolytic Reactions of ZIOC. The transformation is carried out in a simple undivided electrochemical cell under constant current conditions and makes it possible to obtain target pyrazoles in high yields. The key feature of the work is the use of perfluorinated alcohols as solvents, which contributes to the anodic generation of stabilized compounds of hypervalent iodine. Using cyclic voltammetry, NMR monitoring, and control experiments, a possible reaction mechanism was proposed. The synthesis is successfully scaled up to obtain target products in gram quantities. The proposed approach opens up wide opportunities for introducing the promising and well-established chemistry of hypervalent iodine into the practice of electroorganic synthesis.
Stanislav A. Paveliev, Oleg O. Segida, Oleg V. Bityukov, Hai-Tao Tang, Ying-ming Pan, Gennady I. Nikishin, Alexander O. Terent'ev // Adv. Synth. Catal., 2022, 364, 3910-3916. DOI: 10.1002/adsc.202200696.