7095-82-1Relevant academic research and scientific papers
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.
Norpinenes (Bicyclohept-2-enes) from Homobenzvalenes (Tricyclo2,7>hept-3-enes)
Herzog, Clemens,Lang, Reinhard,Brueckner, Dieter,Kemmer, Petra,Christl, Manfred
, p. 3027 - 3044 (2007/10/02)
4,5-Dibromo-(1b) and 4,5-dichlorohomobenzvalene (1c) were converted into the tetrahalonorpinenes 2b, c by elemental bromine.In the case of unsubstituted homobenzvalene (1a) the analogous reaction could be achieved in 1percent yield only by pyridinium perbromide.Treatment of 1a, b as well as of chlorohomobenzvalenyl nitrobenzoate 1d with iodine furnished the diiodonorpinenes 3a - c.However, 7,7-dibromotetracyclo2,4.03,5>heptane (4) and bromine gave the tetrabromo-trans-tricyclo2,4>heptane derivative 5. - On irradiation in the presence of thiophenol, the homobenzvalenes 1a, c, e, f were transformed into the 6-(phenylthio)norpinenes 6a - d.The hydroxyhomobenzvalenes 1g, h afforded the 6-(phenylthio)norpinenes 6e, g as major products, the configuration at C-4 of which is inverted as compared to that of 6b - d.By using 2>-1a it was shown that with respect to stereochemistry the addition of thiophenol does not proceed uniformly.Without irradiation, 1a was consumed by thiophenol rather slowly at 20 deg C with formation of the norcarene derivatives 9 and 10 in addition to 6a. - By treatment with LiAlH4 the dichloro compound 6b gave the monochloro derivative 6h.Both 6b and 6h, however the latter one with a better yield, were converted into unsubstituted norpinene (11a) by means of sodium in liquid ammonia, thus providing a new and preparatively useful synthesis for 11a.Analogously, 6c, d furnished 4-phenylnorpinene (11b).The reaction of norpinenes 3a and 11a with N-bromosuccinimide produced the allylbromides 3d and 11c, respectively. - 13C NMR spectra of the 4-substituted norpinenes revealed a diagnostically important γ-anti-substituent effect.
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.
Carbocyclic thromboxane A2 analogues
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, (2008/06/13)
Stable biologically active thromboxane A2 analogues having the formula: STR1 wherein R1 is OR3, where R3 represents hydrogen or a pharmaceutically acceptable cation or lower alkyl group; or R1 is NR4 R5 where R4 and R5 are the same or different substituents selected from the group consisting of hydrogen and lower alkyl group; and R2 is hydrogen or an --OH group. The thromboxane analogues are potent thrombotic agents, useful in cardiovascular treatment.
