N-Haloamines

Although the three-membered rings with two heteroatoms were discovered only after 1950, they are accessible by very simple procedures familiar to the chemists decades before. The most common starting materials, peracids and N-haloamines, were available to the chemist before 1900 preparation, as well as isolation, follows standard procedures. 

There are several reaction sequences which involve such intramolecular hydrogen abstraction steps. One example is the photolytically intitiated decomposition of N-haloamines in acidic solution, which is known as the Hofinann-Loffier reactionThe reaction leads initially to y-haloamines, but these are usually converted to pyrrolidines by intramolecular nucleophilic substitution ... 

When chlorination is carried out with N-haloamines and sulfuric acid (catalyzed by either UV light or metal ions), selectivity is much greater than with other reagents. In particular, alkyl chains are chlorinated with high regioselectivity at the position next to the end of the chain (the to -1 position). Some typical selectivity values are ... 

A common feature of the reactions in this section is that they serve to introduce functionality at a position remote from functional groups already present. As such, they have proved very useful in synthesizing many compounds, especially in the steroid field (see also 19-2 and 19-14). When N-haloamines in which one alkyl group has a hydrogen in the 4 or 5 position are heated with sulfuric acid, pyrrolidines or piperidines are formed, in a reaction known as the Hofmann-Loffier reaction... 

Halogenation of aromatic compounds Rearrangement of N-haloamines (Orton)... 

The direct introduction of a halogen atom (usually bromine) by means of N-haloamine (generally A -bromosuccinimide) in the allyl position is kno vn as the Wohl-Ziegler reaction ... 

The name Stieglitz rearrangement is generally applied to the rearrangements of trityl N-haloamines and hydroxylamines. These reactions are similar to the rearrangements of alkyl... 

Rearrangement of N-haloamines 8-22 Rearrangement of quaternary ammonium salts and tertiary benzylic amines (Stevens)... 

IODO-GEN (Pierce), first described by Fraker and Speck in 1978, is 1,3,4,6-tetrachloro-3a,6a-diphenylglycouril, an N-haloamine derivative with oxidizing properties similar to those of IODO-BEADS and chloramine-T. The compound is insoluble in aqueous solution, therefore making it a type of solid-phase radioiodination reagent. However, unlike IODO-BEADS, wherein the oxidizing group is immobilized on an-... 

Conditions PhH, dioxane, PhMe, CCI4 etc , 20-110 C 10 min-3 d Scheme 14 -Alkylaziridines from N-haloamines and alkenes... 

HOFMANN. LOEFFLER - FREYTAG PyitoHdineSynthesis Synthesis of pynolidines or piperidines from N-haloamines (free radical reaction). 

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