Halogen Mediated Electrochemical Synthesis: Facial Accesses to Dibenzothiophenes and Spirooxindoles

Abstract

Electrochemical oxidative transformations using a halide as an oxidative mediator are useful for facial accesses to a variety of important organic compounds in the material and biological research fields. We have revealed the unique mediatory ability of anodically generated bromonium ion equivalent in the electrochemical synthesis of the thienoacenes [1].In this presentation we will report two types of transformation using the mediatory system, which enable the formation of a series of crucial compounds. The first one is electrochemical synthesis of dibenzothiophene derivatives, one of the most important frameworks in the field of material science and pharmaceuticals. Several bis(biaryl) disulfides are efficiently converted to dibenzothiophenes by the electrochemical oxidation [2]. The second is the semi-pinacol rearrangement of tetrahydro-β-carbolines affording 3-spirooxindoles, which have unique three-dimensional structures and potent bioactivity [3]. In these reactions, the anodically generated bromonium ion equivalent as a halogen mediator was essential and efficiently promoted the transformation.[1] Mitsudo, K.; Matsuo, R.; Yonezawa, T.; Inoue, H.; Mandai, H.; Suga, S: Angew. Chem. Int. Ed. 2020, 59, 7803−7807.[2] Mitsudo, K.; Tachibana, Y.; Sato, E.; Suga, S: Org. Lett. 2022, 24, 8547−8552.[3] Sato, E.; Kangawa, S.; Mitsudo, K.; Suga, S. Chem. Lett. 2022, 51, 1067–1069.