Metal- and oxidant-free electrochemical dearomatizing spirolactonization and spiroetherification of free arenols Robert Yafele, Somayyeh Sarvi Beigbaghlou, Marcin Kalek Centre of New Technologies University of Warsaw, Poland
The spiro-oxacyclic moiety has drawn considerable attention in synthetic chemistry and medicinal research. 1 This scaffold is present in an extensive range of compounds that are natural or possess a diverse array of biological activities. 2 It is routinely accessed either via the dearomatization of phenols that employs an exogenous oxidant, commonly a hypervalent iodine reagent, or through a transition metal-catalysed reaction. 1,3 Recently, electrochemical synthetic methodologies are gaining traction over these conventional approaches as they are more sustainable and have commercially available standardized instrumentation. 3,4 In this regard, a metal- and exogenous oxidant-free electrochemical oxidative ortho -dearomatization of naphthols and phenols resulting in an intramolecular C–O bond was developed. The established reaction conditions allowed for the use of free arenols as substrates, contrary to the existing alternative procedures which were obligated to employ aryl methyl ethers as substrates or were exclusively confined to para -dearomatization. 4,5 The reaction delivered a range of spirolactones and spiroethers in yields of up to 97%, using a carbon-based anode and a platinum-plated cathode under a constant current, in an undivided cell, and without an inert atmosphere.
References 1. Chen, C. & He, L. Advances in research of spirodienone and its derivatives: Biological activities and synthesis methods. Eur. J. Med. Chem. 203 , 112577 (2020). 2. Quintavalla, A. Spirolactones: Recent Advances in Natural Products, Bioactive Compounds and Synthetic Strategies. Curr. Med. Chem. 25 , 917–962 (2018). 3. Xu, X., Zhong, L., Feng, H. & Van der Eycken, E. V. Application of Metal‐Free Dearomatization Reaction as a Sustainable Strategy to Direct Access Complex Cyclic Compounds. Chem. Rec. (2023) doi:10.1002/tcr.202300101. 4. Yamamoto, T., Saitoh, T., Einaga, Y. & Nishiyama, S. Anodic Oxidation of Phenols: A Key Step for the Synthesis of Natural Products. Chem. Rec. 21 , 2254–2268 (2021). 5. Zhang, C. et al. Electrochemical Oxidation Dearomatization of Anisol Derivatives toward Spiropyrrolidines and Spirolactones. CCS Chem. 4 , 1199–1207 (2022).
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© The Author(s), 2023
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