Pyrrolidines Hofmann-Loeffler-Freytag reaction

The so-called Hofmann-Loeffler-Freytag reaction" " of TV-chloroamines 9 proceeds by a similar mechanism, and is for example used for the synthesis of pyrrolidines 11 ... 

One example of this type of reaction is the photolytically initiated decomposition of (V-chloroamines in acidic solution, which is known as the Hofmann-Loeffler-Freytag reaction 11 The initial products are 8-chloroamines, but these are usually converted to pyrrolidines by intramolecular nucleophilic substitution. 

New cyclizations via photochemically generated aminyl radicals have been reported, including further examples of the Hofmann-Loeffler-Freytag reaction.313 Intramolecular addition of an aminyl radical, generated by photochemically induced nitrogen chlorine bond homoysis, is also accompanied by cyclization as illustrated by the conversion of the unsaturated N-chloroamide 378 to the pyrrolidine 379.314 Piperidine formation can also... 

The synthesis of pyrrolidines by the free radical transformation of (V-chloroamines, the Hofmann-Loeffler-Freytag reaction, is of preparative significance. The key step is the formation of a radical cation which abstracts hydrogen intramolecularly to form a carbon-based radical (Scheme 21(a)). This species then abstracts chlorine from another TV-chloroamine (60JA1657, 50JA2118). The observed positional selectivity for hydrogen abstraction is a consequence of the preferred adoption of a six-membered transition state. A typical conversion achieved is indicated in Scheme 21(b). 

HOFMANN - LOEFFLER FREYTAG Pyrrolidine Synthesis Synthesis of pyrrolidines or piperidines from N-haloamlnes (free radical reaction). 

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