Adsorbed on silica-gel or on other adsorbants (MgSO4, Na2SO4, or Na2CO3), but not in homogeneous solution, pentacarbonyl(methoxyethylidene)chromium combines with simple enynes to give bicyclo[3.1.0]hexanes. The method's usefulness is illustrated by the synthesis of a variety of previously unknown structures from simple hydrocarbons, ethers, and amines.
Platinum- and Gold-Catalyzed Cycloisomerization Reactions of Hydroxylated Enynes
situ. This novel skeletal reorganization process was implemented into a concise total synthesis of the terpenes sabinone (18) and sabinol (19). Furthermore it is shown that conversion of the hydroxylatedenynes into the corresponding acetates followed by reaction with a cationic gold catalyst formed from (PPh3)AuCl and AgSbF6 opens entry into isomeric products bearing the ketone function at the C-2