Chemistry of Selenabenzenes and Related Compounds

Selenabenzene is one of the heterobenzenes in which a selenium atom has replaced a carbon atom of benzene. Selenabenzenes and their benzo-analogs stabilized by an electron-withdrawing group were synthesized in order to study their structures, properties, and reactivities. Cyano-substituted 1- and 2-selenanaphthalenes were isolated as orange crystals, while selenabenzenes with an electron-withdrawing group were too unstable to be isolated at room temperature. Selenabenzenes bearing two stabilizing substituents were recently prepared. The structure of 2,6-dibenzoyl-1-methylselenabenzene is discussed based on IR and NMR spectral data and X-ray crystallographic data. The thermal reaction of selenabenzenes and selenanaphthalenes caused the rearrangement of the Se-alkyl group and dealkylation. They reacted with oxygen to form oxygenated ring-opened products. The reaction of selenanaphthalenes with electron-deficient alkenes and alkynes gave novel ring-transformation products. Selenabenzene derivatives were ylide compounds and changed into selenonium salts on treatment with an acid.