Hofmann–Löffler reaction
In organic chemistry, the Hofmann–Löffler reaction (also referred to as Hofmann–Löffler–Freytag reaction, Löffler–Freytag reaction, Löffler–Hofmann reaction, as well as Löffler's method) is a radical amine cyclization, forming a 5- (or in rare cases, 6-) membered ring. In the reaction, thermal or photochemical decomposition of N-halogenated amine 1 in the presence of a strong acid (concentrated sulfuric acid or concentrated CF3CO2H) generates a nitrogen radical intermediate.