Dehydration of Hexacarbonyldicobalt Protected Tertiary Propargylic Alcohols. Stereo- and Regiochemistry, Synthesis of Enantiomerically Pure Manicone and Normanicone

All articles of this category The stereochemistry and regiochemistry of the dehydration of hexacarbonyl-μ-[η-(3 RS ,5 S )-(+)-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.