The preparation of benzoisothiazolo[1,2-b][1,2]isoquinolin-11-one-1,1-dioxides from dilithiated ortho-toluic acids and lithiated methyl 2-(aminosulfonyl)benzoate

Select dilithiated ortho‐toluic acids were prepared in excess lithium diisopropylamide and condensed with methyl 2‐(aminosulfonyl)benzoate followed by a twofold cyclization of intermediates to afford benzoisothiazolo[1,2‐b][1,2]isoquinolin‐11‐one‐1,1‐dioxides, a new fused‐ring heterocyclic system.