Trichloroisocyanuric acid in 98% sulfuric acid: A superelectrophilic medium for chlorination of deactivated arenes

Trichloroisocyanuric acid (TCCA) reacts with arenes and its reactivity is highly affected by the acid strength of the reaction medium. Deactivated arenes are efficiently chlorinated by TCCA in H2SO4. Our results, along with DFT calculations and 13C NMR spectrometry suggest the formation of a monoprotonated TCCA superelectrophile as the reactive species that can efficiently transfer electrophilic Cl+ to even very weak nucleophiles, such as m-dinitrobenzene.

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► TCCA is safe, stable, and easily available reagent with high atom economy.
► TCCA is monoprotonated by 98% H2SO4.
► DFT calculations support the formation of a superelectrophilic species.
► TCCA in 98% H2SO4 can chlorinate arenes, even strongly deactivated substrates.
► The reactivity of TCCA is regulated by the acid strength of the medium.