Highly Regioselective Dibromination of Amidines With NBS Promoted by Quaternary Ammonium Salts

A highly regioselective dibromination reaction for amidines using N ‐bromosuccinimide (NBS) has been developed, with cetyltrimethylammonium bromide (CTAB) serving as an inexpensive, readily available catalyst. This catalytic system displays excellent reactivity and broad functional group tolerance. Moreover, it boasts several distinct merits, including readily accessible starting materials, straightforward operation, diverse product structures, mild reaction conditions, and applicability to late‐stage functionalization. Notably, it circumvents the requirement for toxic and expensive metal catalysts.