Amine halides, fragmentation reactions

The choice as to which fragment of the molecule to be synthesized should be the vinylic halide and which should be the olefin will depend on several factors. In the cases where elimination to form conjugated dienes is the favored reaction, either possible combination of vinylic halide and olefin may produce the same diene however, different intermediates are involved and in some instances different products may be formed. The situation is more complex when allylic amines are produced since these products always will be different from the two different combinations of reactants. For example, Z-... 

Furthermore, alkyl radicals can be easily obtained from aliphatic iodides or bromides by means of a photoinduced electron transfer reaction with a tertiary amine. The radical formed by fragmentation of the radical anion with concomitant halide ion loss added to a C-C triple bond in the 5-exo-dig cyclization... 

Fragmentations of heterocycles have played an important role in the preparation of amide derivatives. Moderate to good yields of a-hydroxy-amides were obtained on reaction of a-hydroxy-acid aceto-nides with primary amines.N-Alkyl-2-methyl-2-oxazolinium salts (obtained by mixing alkyl halides and 2-methyl-2-oxazoline in dichloromethane) were found to react with sodium benzeneselenolate to yield -(2-phenylselenoethyl)-t -alkylacetamides, which after oxidation to ] -vinyl analogues with sodium metaperiodate in methanol, gave secondary amides on sequential treatment with mercuric acetate in aqueous tetrahydrofuran and sodium borohydride/3M... 

To the more usual homolytic fragmentation of aryl halides (from the excited state or from the radical anion, the well known SrnI reaction, for a recent example see the arylation of aromatics), the heterolytic version of the reaction which produces phenyl cations has more recently joined. A theroretic study on the photodissociation of fluorinated iodobenzenes has been published. The perfluoroallgrlation of various alkenes has been obtained by irradiation in the presence of iodoperfluorobutane. The formation of phenyl cations is exemplified in many arylation reactions and, in the case of o-chlorostannane, also a benzyne has been reported. In the field of polymer chemistry, iodonium salts are model cationic photoinitiators. In particular the truxene-acridine/diphenyl iodonium salt/9-vinylcarbazole combination is able to promote the ringopening polymerization of an epoxide, whereas the truxene AD/allq l halide/amine system is very efficient in initiating the radical photopolymerization of an acrylate. ... 

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