Abstract
The syntheses of the title bicyclic ketone (IV) are described. The Michael-aldol condensation of ethyl acetoacetate (VI) with 2-cyclohexen-1-one (V) afforded a bicyclic β-keto ester, the ketonic cleavage of which gave 1-hydroxybicyclo [3.3.1] nonan-3-one (IX). Removal of the bridgehead hydroxyl in IX via the bromide (X) gave the desired ketone (IV). Another route to IV starting with bromination of adamantane followed by alkaline cleavage was established. Ozonolysis and subsequent ketalization converted 7-methylenebicyclo [3.3.1] nonan-3-one (XVII) into 7-ethylenedioxybicyclo [3.3.1] nonan-3-one (XIX), which was reduced to the desired ketone (IV) by means of the Huang-Minlon reduction. In addition, ozonolysis of 3-methylenebicyclo [3.3.1] nonane (XXII) gained by the Huang-Minlon reduction of XVII as a minor product was also found to give IV in good yield.
