Formal (3+3) cycloaddition of silyl enol ethers catalyzed by trifric imide: domino Michael addition-claisen condensation accompanied with isomerization of silyl enol ethers.

We describe here a Tf₂NH-catalyzed formal (3+3) cycloaddition of silyl enol ethers with acrylates as a new domino reaction. In the domino sequence, the catalyst activates Michael addition, deprotonation of the resulting silyloxonium cation and intramolecular Claisen condensation. It was found that reaction modes significantly depend on the reaction temperature. We also examined the mechanistic detail of the reaction by ¹H-NMR experiment.