Lewis acid catalysed Michael-type addition. A new regio- and diastereo-selective annulation method using methyl vinyl ketone

A new annulation method is presented, involving a boron trifluoride catalysed Michael addition of trialkylsilyl enol ethers to methyl vinyl ketone (MVK) in the presence of a hydroxylic compound. This methodology allows regiospecific 3-oxobutylation of either of the two isomeric enol ethers of mono or di-substituted cyclanones. Octalones 2d, e and hydrindenones 17 with the two alkyl groups in a cis relationship can thus be specifically obtained. This method has been applied to a short and efficient preparation of (±)-dehydrofukinone 10.