Vinyl selenones: annulation agents for the synthesis of six-membered benzo-1,4-heterocyclic compounds

A novel and general approach to six-membered bicyclic benzo fused 1,4-heterocycles is described. The addition-cyclization cascade of benzo 1,2-diols, 1,2-thiols and 2-(benzylamino)phenols with stable and easily available vinyl selenones affords differently substituted 2,3-dihydro-1,4-benzodioxines, benzodithiines and 3,4-dihydro-2H-1,4-benzoxazines in good yields. The same procedure has been extended to the synthesis of 1,2,3,4-tetrahydroquinoxalines. All of these heterocycles are present in a variety of biologically active compounds.