Journal of the Chemical Society. Perkin transactions II p. 119 - 128 (1984)
Update date:2022-08-04
Topics:
Maskill, Howard
Wilson, Alan A.
Bicyclo <2.2.2>octan-2-yl- and exo-bicyclo<3.2.1>octan-2-yl-amines have been deaminated in acetic acid by nitrous acid and via their N-phenyltriazenes; their ethyl N-nitrosocarbamates have also been solvolysed in ethanol.Product distributions by a given method from the structurally isomeric starting materials are similar to each other and to common product distribution obtained from bicyclo<2.2.2>octan-2-yl and exo-bicyclo<3.2.1>octan-2-yl toluene-p-sulphonates.Each amine gives, however, a small but unmistakable excess of the structurally unrearranged product compared (in the case of subtitution) with the distribution obtained from the solvolysis of the corresponding bicyclo-octyl toluene-p-sulphonates. endo-Bicyclo<3.2.1>octan-2-ylamine has also been deaminated in acetic acid by nitrous acid and via its ethyl N-nitrosocarbamate in ethanol.The prouct ratios of these reactions are characteristically different from those of the isomric amines but, as far as substitution is concerned, are similar to what is obtained from endo-bicyclo<3.2.1>octan-2-yl toluene -p-sulphonate.A common mechanism describes all the deaminative reactions.We propose that classical carbonium ions are the initial products of fragmentation of diazo-intermediates.These are intercepted to only a small extent to give products structurally and stereochemically characteristic of the original amines; to an even smaller extent they rearrange to isomeric classical carbonium ions, which in turn may be intercepted.The predominant reaction of the initially formed classical carbonium ions is rearrangement to non-classical isomers.From both becyclo<2.2.2>octan-2-yl- and exo-bicyclo<3.2.1>octan-2-yl-amines, the same unsymmetrical nonclassical carbonium ion is produced as has been implicated in the solvolysis of the corresponding toluene-p-sulphonates. endo-Bicyclo<3.2.1>octan-2-ylamine deamination gives rise to an isomeric symmetrical non-classical carbonium ion, the same one that intervenes in the solvolysis of endo-bicyclo-<3.2.1>octan-2-yl toluene-p-sulphonate.Symmetrical and unsymmetrical non-classical carbonium ions once formed give product ratios largely independent of their origins or modes of formation although the symmetrical one appears to undergo a small extent of isomerization to the (more stable) unsymmetrical species.These results are contrasted with those obtained from simple carbocyclic systems (without branching at the β-carbon) in which deamination and toluene-p-sulphonate solvolysis give characteristically different and unrelated product distributions.
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