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@ARTICLE{Scholz:9771,
      author       = {Scholz, R. and Hellmann, G. and Rohs, S. and Raabe, G. and
                      Raabe, G. and Runsink, J. and Özdemir, D. and Luche, O. and
                      Heß, T. and Giesen, A.W. and Atodiresei, J. and Lindner,
                      H.J. and Gais, H.-J.},
      title        = {{E}xperimental and {T}heoretical {S}tudy of the
                      {E}nantiomerization {B}arrier of a-{S}ulfonyl {C}arbanions
                      and {D}etermination of the {S}tructure of {L}ithium
                      a-tert-blutylsulfonyl {C}arbanion {S}alts in {S}olution and
                      the {C}rystal},
      journal      = {European journal of organic chemistry},
      volume       = {2010},
      issn         = {1434-193X},
      address      = {Weinheim},
      publisher    = {Wiley-VCH Verl.},
      reportid     = {PreJuSER-9771},
      pages        = {4559 - 4587},
      year         = {2010},
      note         = {This research was supported by the Deutsche
                      Forschungsgemeinschaft (DFG), the Volkswagen Foundation, and
                      Fonds der Chem'schen Industrie. We thank Professor Dr. H.
                      Fritz and Dr. D. Hunkler for NMR measurements, Professor Dr.
                      W. Bauer for cryoscopy measurements and valuable
                      experimental advice, Dr. E. Keller for a version of SCHAKAL,
                      and C. Vermeeren and D. Wolters for the preparation of the
                      graphics. We are grateful to Professor Dr. H. J. Reich for
                      his assistance in the analysis of the NMR spectra of the
                      salt rac-9 in the presence of HMPA and for information
                      concerning his unpublished results of a NMR spectroscopic
                      study on the behaviour of lithium S-phenylsulfonyl carbanion
                      salts towards H M PA.},
      abstract     = {Dynamic NMR (DNMR) spectroscopy of [(RC)-C-1(R-2)SO2R3]Li
                      (R-1, R-2 = alkyl, phenyl; R-3 = Ph, tBu, adamantyl, CEt3)
                      in [D-8]THF has shown that the S-tBu, S-adamantyl, and
                      S-CEt3 derivatives have a significantly higher
                      enantiomerization barrier than their S-Ph analogues.
                      C-alpha-S bond rotation is most likely the rate-determining
                      step of the enantiomerization of the salts bearing a bulky
                      group at the S atom and two substituents at the C-alpha,
                      atom. Ab initio calculations on [Me(Ph)SO(2)tBu](-) gave
                      information about the two C-alpha-S rotational barriers,
                      which are dominated by steric effects. Cryoscopy of
                      [(RC)-C-1(R-2)SO(2)tBu]Li in THF at -108 degrees C revealed
                      the existence of monomers and dimers. X-ray crystal
                      structure analysis of the monomers and dimers of
                      [(RC)-C-1(R-2)SO(2)tBu]Li center dot L-n (R-1 = Me, Et,
                      tBuCH(2), PhCH2, tBu; R-2 = Ph, L = THF, 12-crown-4, PMDTA)
                      and [(RC)-C-1(R-2)SO2Ph]Li center dot 2diglyme [R-1 = R-2 =
                      Me, Et; R-1-R-2 = (CH2)(5)] showed them to be O-Li contact
                      ion pairs (CIPs). The monomers and dimers have a C-alpha-S
                      conformation in which the lone-pair orbital at the C-alpha
                      atom bisects the O-S-O angle and a significantly shortened C
                      -S bond. The C-alpha atom of [(RC)-C-1(R-2)SO2R3]center dot
                      L-n (R-1 = Ph; R-3 = Ph, tBu) is planar, whereas the C-alpha
                      atom of [(RC)-C-1(R-2)SO2R3]Li center dot I., (R-1 = R-2 =
                      alkyl) is strongly pyramidalized in the case of R-3 = Ph and
                      most likely planar for R-3 = tBu. Ab initio calculations on
                      [MeC(Me)SO2R](-) gave a pyramidalized C-alpha atom for R =
                      Me and a nearly planar one for R = CF3 and tBu. The
                      [(RC)-C-1(R-2)SO(2)tBu]Li salts were characterized by H-1,
                      C-13, and Li-6 NMR spectroscopy.H-1{H-1} and Li-6{H-1} NOE
                      experiments are in accordance with the existence of O-Li
                      CIPs. H-1 and C-13 NMR spectroscopy of
                      [(RC)-C-1(R-2)SO(2)tBu]Li in [D-8]THF at low temperatures
                      showed equilibrium mixtures of up to five different species
                      being most likely monomeric and dimeric O-Li CIPs with
                      different configurations. According to Li-7 NMR
                      spectroscopy, the addition of HMPA to [MeC(Ph)SO(2)tBu]Li in
                      [D8ITHF at low temperatures causes the formation of the
                      separated ion pair [MeC(Ph)SO(2)tBu]Li(HMPA)(4).},
      keywords     = {J (WoSType)},
      cin          = {IEK-7},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK491},
      shelfmark    = {Chemistry, Organic},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000281723200004},
      doi          = {10.1002/ejoc.201000409},
      url          = {https://juser.fz-juelich.de/record/9771},
}