Convergent access to bis-spiroacetals through a Sila-Stetter-ketalization cascade.

An NHC-catalyzed sila-Stetter reaction between aliphatic acylsilanes and vinylketones bearing silyl ether substituents affords functionalized 1,4-diketones, which upon treatment under acidic conditions leads to the corresponding bis-spiroacetals. The two-step sequence may also be carried out in a one-pot operation leading to high yields of the desired bis-spiroacetals.