- Rearrangement and Cleavage of the Grignard Reagent from 5-(Chloromethyl)norbornene
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The Grignard reagents 1-Mg and 2-Mg from endo- and exo-5-(chloromethyl)norbornene rearrange with ring cleavage on heating to yield an allylcyclopentenyl organomagnesium compound (3-Mg).This, in turn, undergoes competitively a variety of reactions, including an alternative cyclization to a bicyclooctene organomagnesium (4-Mg) and formal loss of hydrogen or propene to produce allylcyclopentadienyl- (5-Mg) and cyclopentadienylmagnesium compounds.Endo and exo isomers 1-Mg and 2-Mg rearrange at comparable rates and are partially interconverted, probably via their cleavage and recyclization.Mechanistic possibilities are discussed.
- Hill, E. Alexander,Hsieh, King,Condroski, Kevin,Sonnentag, Heidi,Skalitzky, Donald,Gagas, Donald
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p. 5286 - 5292
(2007/10/02)
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- TRANSFORMATIONS OF CYCLOPROPANE IN RIGID HYDROCARBON SYSTEMS USING PLATINUM(II)
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Using the cyclopropane adducts of the norbornyl system, platinacyclobutane complexes were prepared.In this article, the reactions of these platinum(IV) complexes with heat, CH2N2 and DMSO are discussed.In each case, a unique olefinic product has been produced.In another reaction, the platinacyclobutane of phenylcyclopropane is treated with CH2N2 to produce styrene.
- Jennings, P. W.,Ekeland, R. E.,Waddington, M. D.,Hanks, T. W.
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p. 429 - 436
(2007/10/02)
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- DEAMINATION OF BICYCLOOCTAN-2-YL- AND BICYCLOOCTAN-2-YL-AMINES. EVIDENCE FOR CLASSICAL PRECURSORS OF NON-CLASSICAL CARBONIUM IONS
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Bicyclo octan-2-yl- and exo-bicyclooctan-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 bicyclooctan-2-yl and exo-bicyclooctan-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-Bicyclooctan-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-bicyclooctan-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 becyclooctan-2-yl- and exo-bicyclooctan-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-Bicyclooctan-2-ylamine deamination gives rise to an isomeric symmetrical non-classical carbonium ion, the same one that intervenes in the solvolysis of endo-bicyclo-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.
- Maskill, Howard,Wilson, Alan A.
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p. 119 - 128
(2007/10/02)
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- DEAMINATION OF ENDO - AND EXO-BICYCLOOCTAN-3-YLAMINES AND THEIR DERIVATIVES
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Bicyclooctan-3-ylamines have been deaminated in acetic acid by nitrous acid and via their N-phenyltriazines; their ethyl N-nitrosocarbabamates have also been solvolysed in ethanol.The exo-isomers give mainly unrearranged substitution, some elimination, and very little rearrangement.The unrearranged substitution is derived from both the solvent (the external nucleophile, either acetic acid or ethanol) and internal nucleophile liberated in the deaminative fragmentation step (water from the nitrous acid reaction, aniline from the triazene, and ethyl carbonate from the nitrosocarbamate).It is of predominantly retained configuration i n all three reactions with the solvents, and, as demonstrated in the solvolysis, with the internal nucleophile.The endo-isomers give mainly elimination, some unrearranged substitution, and appereciable rearrangement.The solvent-derived unrearranged substitution is with predominant inversion of configuration in all three reactions whereas that from the internal nucleophile, established by the nitrosocarbamate solvolysis, is predominantly with retention.Rearangement from both endo- and exo-compounds is best explained in terms of hydride shift from the first formed carbonium ions (in nitrogen-separated complex ion-pairs with hydrogen-bonded anions) produced in the deaminative fragmentation.This gives rearranged classical bicyclooctan-2-yl carbonium ions which, in competition with nucleophilic capture and proton loss, undergo further stepwise rearrangement to a common unsymmetrical non-classical carbonium ion.The non-classical cation and its classical precursors (which, from exo-and endo-substrates, differ in the location of the counter-anion) give rise to substitution products derived from solvent and the internal nucleophile.The non-classical carbonium ion also gives some tricyclo2,7>octane.The high yields of internal substitution products from both endo- and exo-compounds rule out long lived intermediates such as diazonium ions.
- Maskill, H.,Wilson, Alan A.
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p. 1369 - 1376
(2007/10/02)
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