Novel condensation of ketones with homoallyl alcohols catalyzed by Hg (OTf) 2 has been developed, generating a 6-membered ring ether alcohol, bisether, and olefins. The reaction is initiated b hemiacetal formation, and cyclization of the resulting oxonium cation provides the 6-membered ring carbocation as a common intermediate. Thus, it is a catalytic Prins-type condensation of non-activated homoallyl alcohols and ordinary ketones.
![4-methylidene-1-oxaspiro[5.5]undecane Structure](https://image.chemsrc.com/caspic/072/62062-84-4.png)