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

Abstract

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.

Electrochemical cascade migratory versus ortho-cyclization of 2-alkynylbenzenesulfonamides

“…Initially, our extensive optimization of reaction conditions (see ESI † ) disclosed that the 2-alkynylbenzenesulfonamide (1a) underwent an electrochemical cascade ortho -cyclization 18 to afford the corresponding heterocycle (2a) in 59% yield, whose chemical structure was confirmed by the X-ray diffraction analysis ( Scheme 2 ). 19 Among several solvents tested, the combination of dichloroethane (DCE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) mixed solvents afforded the cleanest reaction system that facilitated the purification of products. The use of HOAc was crucial to the observed reactivity since HOAc served as the sacrificial oxidant and the resultant acetate acted as a base in the following proton-coupled electron transfer (PCET) process, which was further substantiated both by the cyclic-voltammetry and nuclear-magnetic-resonance studies (see ESI † ).…”