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Synthesis 1996; 1996(1): 141-144
DOI: 10.1055/s-1996-4172
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Convenient Synthesis of Enantiomerically Enriched (Oxybutenyl)stannanes and Their Lewis Acid Catalyzed Homoaldol Reactions

Holger Paulsen, Claudia Graeve, Dieter Hoppe*
  • *Organisch-chemisches Institut der Universität Münster, Corrensstraße 40, D-48149 Münster, Germany, Fax +49(251)839772
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Publication Date:
31 December 2000 (online)

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(E)-But-2-enyl N,N-diisopropylcarbamate10 (5), after deprotonation to its lithium/(-)-sparteine complex 6, yields with trialkyltin chlorides mixtures of the 3-oxy- and 1-oxy-substituted, enantiomerically enriched allylstannanes (S)-8 and (R)-9. (R)-8 is obtained with high regioselectivity and enantiomeric purity (95% ee) via a delithiotitanation (inversion) and detitanostannylation (anti-SE’)sequence. The titanium tetrachloride mediated condensation of (S)- or (R)-8 with aldehydes or ketones proceeds via titanodestannylation to yield (Z)-anti-homoaldol products 11 with complete chirality transfer.

allyl carbamates - (-)-sparteine-induced lithiation - enantioenriched allylstannanes - 1,3-chirality transfer - enantioselective homoaldol reaction