Reactions of 2,2′-diselenobis(N-alkylbenzamides) with peroxides: A free-radical synthesis of Ebselen and related analogues

Abstract

N-Alkyl-2-triphenylstannylbenzamides (3, R = Hex, Ph, iso-Pro, tert-Bu), prepared from the corresponding 2-benzylselenobenzamides, react with benzoyl peroxide in benzene, under reflux, to afford the 2,2′-diselenobis(N-alkylbenzamides) ( 4) in 54–87% yield. Further treatment with benzoyl peroxide or di- tert-butyl peroxide in benzene or chlorobenzene affords the N-alkyl-1,2-benzisoselenazol-3(2H)-ones ( 2) in 76–85% yield. This transformation presumably involves intermediate amidyl radicals which undergo intramolecular homolytic substitution at selenium to afford the product.