7095-82-1Relevant articles and documents
Geometrical Dependence of γ-Trimethylsilyl Groups on Norbornyl Solvolyses. Rapid-Injection Kinetic Methods for Solvolyses of Unstable Mesylates
Bentley, T. William,Kirmse, Wolfgang,Llewellyn, Gareth,Soellenboehmer, Frank
, p. 1536 - 1540 (1990)
Solvolytic rate constants in ethanol and aqueous ethanol mixtures are reported for solvolyses of unstable mesylates, prepared in situ from tert-butyl alcohol, and the following 6-trimethylsilyl (TMS) substituted 2-exo-norbornanols: 6-exo- and 6-endo-(trimethylsilyl)-substituted and 6,6-bis(trimethylsilyl)-substituted.These kinetic data for ethanol at 25 deg C show similar relative rates to those observed for solvolyses of the corresponding p-nitrobenzoates in 97percent w/w trifluoroethanol/water at 100 deg C; there are up to ca. 100-fold larger rate enhancements due to γ-silicon than those previously reported for acyclic and monocyclic systems; e.g. in ethanol 3.3 1E4 for 6-exo-(trimethylsilyl)-2-exo-norbornyl mesylate; these results support recent experimental and theoretical studies showing that a W conformation is preferred.In contrast, for solvolyses of the corresponding 2-endo-brosylates in 80percent ethanol/water and in 97percent trifluroethanol, the 6-exo-TMS substituent shows only a 2-4-fold rate enhancement, and the 6-endo-TMS substituent shows rate retardation.Additional rate constants are reported for conventional solvolyses of mesylates of 1-adamantanol, 2-exo-norbornanol, and 6-exo-(trimethylsilyl)-2-endo-norbornanol.These data for 6-exo-TMS cmpounds establish a 2-exo/2-endo-norbornyl rate ratio of > 1E6, the largest observed for an unhindered secondary system.
Si-induzierte Norbornyl-Norpinyl-Umlagerungen
Kirmse, Wolfgang,Soellenboehmer, Frank
, p. 1728 - 1730 (2007/10/02)
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Norpinyl-Norbornyl Rearrangements: Bicycloheptane, 4-Methyl- and 6-Methylbicycloheptane Derivatives
Kirmse, Wolfgang,Siegfried, Rainer,Wroblowsky, Heinz-Juergen
, p. 1880 - 1896 (2007/10/02)
Norpinyl-norbornyl rearrangements have been induced by solvolysis of the 2-norpinyl nitrobenzoates 15b, c and by decomposition of norpinane-, 4-methylnorpinane-, and 6-methylnorpinane-2-diazonium ions (19, 49, 64, 65).No fragmentation to monocyclic cations was observed.The yield of norpinyl products was minimal in water (s processes).With 64 and 65, migration of the bridge trans to the leaving group predominated strongly.The rearrangements afforded exo-2- and endo-2-norbornyl products in comparable quantities.The exo/endo rates depended on the nucleophilicity of the solvent but were little effected by methyl substitution at the migrating carbon.We propose the 7-bridged norbornyl cation (21) as the endo-selective intermediate which rearranges to the exo-selective 6-bridged (or rapidly equilibrating) norbornyl cation (22, 23) in competition with solvent capture.Ion-pair collapse (cf. 15b) accentuates the endo-selectivity.However, ion pairing cannot be the only source of endo-2-norbornyl products, as shown by the deamination reactions in water.
