Hofmann‐Löffler‐Freytag Reaction

Abstract

The synthesis of pyrrolidine or piperidine derivatives by thermal or photochemical decomposition of the protonated aliphatic N ‐haloamines is generally known as Hofmann–Löffler–Freytag reaction. Many experimental evidences support the radical mechanism of this reaction, such as the initiation of the reaction by either photo‐irradiation or traditional radical initiators and the inhibition of reaction by oxygen. In this reaction, hydrogen abstraction is the chain‐propagating step. Presently, many other methods have been established to generated aminium radicals. This reaction has been extended to amidyl radical, sulfonamidyl radical, and other nitrogenous radicals. This reaction has been applied for the preparation of substituted pyrrolidines and piperidines.