8-Oxabicyclo- 3.2.1 octene-6-one

Alkyne hexacarbonyldicobalt complexes. The complexes of alkynes with Co2(CO)84 react with 2,5-dihydrofuranes to give 3-oxabicyclo[3.3.0]-7-octene-6-ones in high yield (equation I) when the reaction is conducted under a CO atmosphere. 

Cationic cycloadditions. Ionization of p-benzoquinone monoacetals is induced by MejSiOTf in highly polar media (LiClO /EtOAc) and the carbocations are captured in situ by alkenes to give bicyclo[3.2.1]octene derivatives. A synthesis of 2-(l -phenylethoxy)-8-oxabicyclo[3.2.1]oct-6-en-3-one in good enantiomeric purity from furan and a mixed acetal of 2-(triethylsiloxy)acrolein (prepared from pyruvaldehyde dimethylacetal in three steps) is promoted by MejSiOTf. 

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