Regioselective ring opening of alkylidenecyclopropanone silyl acetals

Alkylidenecyclopropanone silyl acetals are readily available from the reaction of an alkylidenemethyliodonium salt and ketene silyl acetals in the presence of triethylamine. The three different C–C bonds of the cyclopropane ring can be selectively cleaved with HCl, Lewis acid, or fluoride. The alkylideneallyl cation formed via the cleavage of C2–C3 bond with Lewis acids shows further selectivity in reacting with a nucleophile.