text: The reaction was discovered in the 1970s as part of a synthetic route to certain prostanoids. The reaction required tin tetrachloride and a stoichiometric amount of Wilkinson's catalyst:
  An equal amount of a cyclopropane was formed as the result of decarbonylation. 
  The first catalytic application involved cyclization of 4-pentenal to cyclopentanone using (again) Wilkinson's catalyst. In this reaction the solvent was saturated with ethylene. 
  :CH=CHCHCHCHO   →   (CH)CO