Abstract Silyl enol ethers bearing a nitrogen atom protected by an electron-withdrawing group give in high yield a Micheal-type addition with hemiacetal vinylog or a mixture of methyl vinyl ketone and an alcohol in the presence of boron trifluoride etherate as a catalyst. The aza-1, 5-diketones so prepared can be cyclised leading to aza-enones precursors of some biologycally active structures.
![ethyl 1,4-dioxa-8-azaspiro[4.5]decane-8-carboxylate Structure](https://image.chemsrc.com/caspic/406/51787-77-0.png)