Ring opening alkylidenecyclopropanone

Ring opening reaction of alkylidenecyclopropanone acetals readily proceeds in the presence of Lewis or Bransted acids to produce l-alkylidene-2-oxyallyl cation, which is provided for the reaction with nucleophiles such as chloride, alcohols, siloxyalkenes, and furans. The reaction of this cation with the carbon nucleophiles gives products of [4 + 3] and [3 + 2] cycloaddition as well as those of nucleophilic addition. The modes of addition reactions are controlled by the oxy group of the cation and by the reaction conditions including solvent. 

Scheme 5. Regioselective ring opening of alkylidenecyclopropanone acetal...

Fujita and Okuyama et al. showed the regioselective ring-opening reaction of alkylidenecyclopropanone silyl acetal with SnCU [32]. The regioselectivities speciflcally depend on the structure of the substrates (Scheme 10.12). 

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