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Manfred Christl - One of the best experts on this subject based on the ideXlab platform.

  • solvolysis of tricyclo 4 1 0 02 7 hept 4 en 3 yl and tricyclo 4 1 0 02 7 hept 3 yl methanesulfonates and p nitrobenzoates remarkably small enthalpy difference between the c7h7 cations tricyclo 4 1 0 02 7 hept 4 en 3 yl and 7 norbornadienyl
    Liebigs Annalen, 1997
    Co-Authors: William T Bentley, Gareth Llewellyn, Simon J Norman, Ralf Kemmer, Ulrike Kunz, Manfred Christl
    Abstract:

    In an extension of previous work, tricyclo[4.1.0.02,7]heptan-3-ol (5) was synthesised in four steps from benzvalene. Methanesulfonates 12 and 6b, c, prepared from 5 and 4-halotricyclo[4.1.0.02,7]hept-4-en-3-ols 4b, c, were too unstable to be isolated, but were unambiguously characterised by their NMR spectra. On treatment of the unsubstituted tricycloheptenol 4a with Methanesulfonyl Chloride, the expected mesylate 6a could not be observed. Even at −40°C, only its consecutive products 3-chlorotricyclo[4.1.0.02,7]hept-4-en (7a) and 7-chloronorbornadiene (8a) were discernible. The analogous reaction of 6b occurred only at room temperature, with formation of the dichlorotricycloheptene 7b and the dichloronorbornadiene 8b. Rearrangement products of 6b and 12 were the chloronorbornadiene mesylate 10b and anti-7-norbornenyl mesylate (13), respectively. – The solvolysis of 6b, c in aqueous ethanol and of 6b in 2,2,2-trifluoroethanol (TFE) gave nonrearranged products exclusively, i.e. the alcohols 4b, c, the ethyl ethers 17b, c, and the trifluoroethyl ether 18b. In contrast, from 12 only rearranged products arose, namely anti-7-norbornenol (30) and its ethyl ether 31. The solvolysis of the unsubstituted tricycloheptenyl p-nitrobenzoate 11a in 80% aqueous ethanol proceeded about equally fast in parallel reactions with cycloalkyl-oxygen and acyl-oxygen cleavage. In addition to the tricycloheptenol 4a, the tricycloheptenyl ethyl ether 17a, ethyl 7-norbornadienyl ether (19), 7-norbornadienyl p-nitrobenzoate (20), and ethyl p-nitrobenzoate were formed. No acyl-oxygen cleavage took place in TFE as solvent, where the tricycloheptenyl trifluoroethyl ether 18a, 20, 7-norbornadienyl trifluoroethyl ether (21), and the cyclopentadienylvinyl trifluoroethyl ethers 22/23 were produced. A new mechanism is proposed for the route to the major products 22/23 via the intermediate 7-norbornadienyl cation (9a), which was attacked by TFE at the two-membered bridge stabilising the positive charge. Thus formed, tricyclo-[3.2.0.02,7]hept-3-en-endo-6-yl trifluoroethyl ether (24) underwent a Diels-Alder cycloreversion generating the cyclopentadienylvinyl trifluoroethyl ether 25, the immediate precursor of 22/23. – From kinetic data for these processes and thermochemical data for appropriate hydrocarbons, the enthalpy difference between the C7H7 cations, tricyclo-[4.1.0.02,7]hept-4-en-3-yl (3a) and 7-norbornadienyl (9a), was calculated to be only 8 kcal mol−1.

Patricia Aikins Murphy - One of the best experts on this subject based on the ideXlab platform.

Wt Hua - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis of novel chiral bisoxazoline ligands containing 2,5-diaryl-1,3,4-oxadiazole and enantioselective cyclopropanation of styrene
    synthesis stuttgart, 2002
    Co-Authors: Zy Wang, Wt Hua
    Abstract:

    Practical synthesis of chiral C-2-symmetric substituted bisoxazoline ligands containing 2,5-diaryl-1,3,4-oxadiazole units was investigated. Five chiral bisoxazoline ligands containing 2,5-diphenyl-1,3,4-oxadiazole have been synthesized from 2,5-di-(o-carboxylphenyl)-1,3,4-oxadiazole and amino alcohols by Methanesulfonyl Chloride or p-toluenesulfonyl Chloride assisted cyclization via hydroxy amide intermediate. Preliminary examination of copper complexes of new ligands as chiral catalysts in the enantioselective cyclopropanation of styrene with ethyl diazoacetate was performed. Enantioselectivities up to 35% ee and 87% ee for trans- and cis-2-phenylcyclopropanecarboxyl ate, respectively were observed.Chemistry, OrganicSCI(E)EI15ARTICLE162347-235

William T Bentley - One of the best experts on this subject based on the ideXlab platform.

  • solvolysis of tricyclo 4 1 0 02 7 hept 4 en 3 yl and tricyclo 4 1 0 02 7 hept 3 yl methanesulfonates and p nitrobenzoates remarkably small enthalpy difference between the c7h7 cations tricyclo 4 1 0 02 7 hept 4 en 3 yl and 7 norbornadienyl
    Liebigs Annalen, 1997
    Co-Authors: William T Bentley, Gareth Llewellyn, Simon J Norman, Ralf Kemmer, Ulrike Kunz, Manfred Christl
    Abstract:

    In an extension of previous work, tricyclo[4.1.0.02,7]heptan-3-ol (5) was synthesised in four steps from benzvalene. Methanesulfonates 12 and 6b, c, prepared from 5 and 4-halotricyclo[4.1.0.02,7]hept-4-en-3-ols 4b, c, were too unstable to be isolated, but were unambiguously characterised by their NMR spectra. On treatment of the unsubstituted tricycloheptenol 4a with Methanesulfonyl Chloride, the expected mesylate 6a could not be observed. Even at −40°C, only its consecutive products 3-chlorotricyclo[4.1.0.02,7]hept-4-en (7a) and 7-chloronorbornadiene (8a) were discernible. The analogous reaction of 6b occurred only at room temperature, with formation of the dichlorotricycloheptene 7b and the dichloronorbornadiene 8b. Rearrangement products of 6b and 12 were the chloronorbornadiene mesylate 10b and anti-7-norbornenyl mesylate (13), respectively. – The solvolysis of 6b, c in aqueous ethanol and of 6b in 2,2,2-trifluoroethanol (TFE) gave nonrearranged products exclusively, i.e. the alcohols 4b, c, the ethyl ethers 17b, c, and the trifluoroethyl ether 18b. In contrast, from 12 only rearranged products arose, namely anti-7-norbornenol (30) and its ethyl ether 31. The solvolysis of the unsubstituted tricycloheptenyl p-nitrobenzoate 11a in 80% aqueous ethanol proceeded about equally fast in parallel reactions with cycloalkyl-oxygen and acyl-oxygen cleavage. In addition to the tricycloheptenol 4a, the tricycloheptenyl ethyl ether 17a, ethyl 7-norbornadienyl ether (19), 7-norbornadienyl p-nitrobenzoate (20), and ethyl p-nitrobenzoate were formed. No acyl-oxygen cleavage took place in TFE as solvent, where the tricycloheptenyl trifluoroethyl ether 18a, 20, 7-norbornadienyl trifluoroethyl ether (21), and the cyclopentadienylvinyl trifluoroethyl ethers 22/23 were produced. A new mechanism is proposed for the route to the major products 22/23 via the intermediate 7-norbornadienyl cation (9a), which was attacked by TFE at the two-membered bridge stabilising the positive charge. Thus formed, tricyclo-[3.2.0.02,7]hept-3-en-endo-6-yl trifluoroethyl ether (24) underwent a Diels-Alder cycloreversion generating the cyclopentadienylvinyl trifluoroethyl ether 25, the immediate precursor of 22/23. – From kinetic data for these processes and thermochemical data for appropriate hydrocarbons, the enthalpy difference between the C7H7 cations, tricyclo-[4.1.0.02,7]hept-4-en-3-yl (3a) and 7-norbornadienyl (9a), was calculated to be only 8 kcal mol−1.

Vijaykumar D. - One of the best experts on this subject based on the ideXlab platform.