ChemInform Abstract: Thermal Reactions of Cyclopropenone Ketals. Key Mechanistic Features and Scope of the Cycloaddition Reactions of Delocalized Singlet Vinylcarbenes: Three‐Carbon 1,1‐/1,3‐Dipoles.

As exemplified in the scheme for (IIIb), the title compounds (III) (prepared from (I)) react with olefins (V) and (VII) bearing an electron‐withdrawing group by thermal generation of a π‐delocalized singlet vinylcarbene (IV) and subsequent (2 + 1) cycloaddition to give mainly cis adducts (VI) and (VIII).