TEMPO and its derivatives are disclosed as active oxygen-centered Lewis base catalysts for electrophilic halogenation of olefins, alkynes, and aromatics. These catalysts are stable, readily available, and reactive enough to activate haloniums including Br+, I+ and even Cl+ reagents. This catalytic system was applicable to various halogenations including haloarylation of olefins or dibromination of alkynes, which were rarely realized in the Lewis base catalysis. The mild reaction conditions and good functional group tolerance made the present method very useful in intramolecular haloarylation of olefins, aromatic halogenation of arenes, dibromination of olefins and alkynes with excellent selectivity and efficiency. The mechanistic studies revealed a synergistic activation model, and may promote the design and development of new Lewis base catalysis.

Nitroxides catalyzed efficient and selective halogenation

ACS Spring Meeting 2021

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