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Synthesis 1991; 1991(8): 633-636
DOI: 10.1055/s-1991-26531
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Dehydration of Hexacarbonyldicobalt Protected Tertiary Propargylic Alcohols. Stereo- and Regiochemistry, Synthesis of Enantiomerically Pure Manicone and Normanicone

Gagik G. Melikyan* , Alfred Mineif, Otto Vostrowsky, Hans Jürgen Bestmann
  • *Institute of Organic Chemistry, University Erlangen-Nürnberg, Henkestr. 42, D-8520 Erlangen, Germany
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Publication Date:
29 April 2002 (online)

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The stereochemistry and regiochemistry of the dehydration of hexacarbonyl-μ-[η-(3RS,5S)-(+)-3,5-dimethyl-1-heptyn-3-ol]dicobalt (Co-Co) and hexacarbonyl-μ-[η-(4RS,6S)-(+)-4,6-dimethyl-7-octyn-4-ol] dicobalt (Co-Co) with diethyl ether-boron trifluoride complex, trifluoroacetic acid or phosphorus(V) oxide have been investigated. The distribution of the isomeric products [(E)-enynes 41-86%, (Z)-enynes 9-59%, enynes with exomethylene group 0-9%] is dependent on the substrate structures as well as the nature of dehydrating agent. By acid-catalyzed hydration of the corresponding enynes enantiomerically pure (E,S)-(+)- 4,6-dimethyl-4-octen-3-one (manicone) and (E,S)-(+)-3,5-dimethyl-3- hepten-2-one (normanicone) have been synthesized.