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@ARTICLE{Scholz:9772,
      author       = {Scholz, R. and Hellmann, G. and Rohs, S. and Özdemir, D.
                      and Raabe, G. and Vermeeren, C. and Gais, H.-J.},
      title        = {{E}nantioselective {S}ynthesis, {C}onfigurational
                      {S}tability, and {R}eactivity of {L}ithium
                      a-tert-{B}utylsulfonyl {C}arbanion {S}alts},
      journal      = {European journal of organic chemistry},
      volume       = {2010},
      issn         = {1434-193X},
      address      = {Weinheim},
      publisher    = {Wiley-VCH Verl.},
      reportid     = {PreJuSER-9772},
      pages        = {4588 - 4616},
      year         = {2010},
      note         = {This research was supported by the Deutsche
                      Forschungsgemeinschaft (DEG), Volkswagen Foundation, and
                      Fonds der Chemischen Industrie. We thank D. Wolters for his
                      help with the graphics.},
      abstract     = {The reactions of enantiopure S-tert-butyl sulfones of the
                      type (RCH)-C-I(R-2)SO(2)tBu (<= 99 $\%$ ee) with
                      lithiumorganyl compounds gave the corresponding chiral
                      alpha-sulfonyl carbanion salts [(RC)-C-1(R-2)SO(2)tBu]Li
                      with >= 94 $\%$ ee. The enantioselectivity of the
                      deprotonation of the phenyl-but not dialkyl-substituted
                      sulfones is strongly dependent on the nature of the
                      lithiumorganyl. Because of this observation and the strong
                      decrease in enantioselectivity in the presence of TMEDA and
                      HMPA, we propose an intramolecular proton transfer following
                      complexation of the sulfone by RLi. Racemization of
                      (RC)-C-1(R(2))SO(2)tBu]Li follows first-order kinetics and
                      seems to be mainly an enthalpic process with a small
                      negative activation entropy, as revealed by polarimetric
                      measurements at low temperatures. This is in accordance with
                      C-alpha-S bond rotation as the rate-determining step. The
                      salts [(RC)-C-1(R-2)SO(2)tBu]Li have half-lives of
                      racemization in the order of several hours at -105 degrees
                      C. The deuteriation of the salts at -105 degrees C with
                      CF3CO2D proceeded with enantioselectivities of >= 94 $\%$
                      ee, the magnitude of which was not significantly affected by
                      the presence of TMEDA and HMPA. The salts also reacted with
                      carbon-based electrophiles at low temperatures with high
                      enantioselectivity. The conversion of (RCH)-C-1(R-2)SO(2)tBu
                      via [(RC)-C-1(R-2)SO(2)tBu]Li to (RC)-C-1(R-2,E)SO(2)tBu,
                      which involves the loss of stereogenicity at the
                      alpha-stereogenic center and its reestablishment upon
                      reaction of the chiral carbanian with electrophiles,
                      occurred with high overall enantioselectivity. Electrophiles
                      attack the anionic C atom of [(RC)-C-1(R-2)SO(2)tBu]Li with
                      high selectivity on the side syn to the O atoms and anti to
                      the tert-butyl group. The reactivity of the
                      dialkyl-substituted salts [(RC)-C-1(R-2)SO(2)tBuiLi (R-1,
                      R-2 = alkyl) is significantly higher than that of the
                      benzylic salts [RC(Ph)SO(2)tBu]Li (R = alkyl) and the
                      HMPA-coordinated SIPs of [MeC(Ph)SO(2)tBu]Li are
                      significantly more reactive towards EtI than the
                      corresponding O-Li contact ion pairs.},
      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:000281723200005},
      doi          = {10.1002/ejoc.201000410},
      url          = {https://juser.fz-juelich.de/record/9772},
}