A One-Pot Access to Benzo[b][1,4]selenazines from 2-Aminoaryl Diselenides

Different 2-sulfonylaminoaryl diselenides substituted with electron-withdrawing or -donating groups are transformed in one pot into benzo[b][1,4]selenazines. The reaction uses a substoichiometric amount of Cu(OTf)2, and the mechanism involves a base-mediated 1,4-elimination at selenium with the generation of an o-iminoselenoquinone and a 2-sulfonylaminoselenolate anion. The former is a dienic species that can react with electron-rich dienophiles to give the target cycloadducts. The latter is oxidised by air back to the starting diselenide, allowing its complete consumption. A preliminary investigation of the GPx-like activity of a selected selenazine is also described.