Tin(IV) Chloride Catalyzed Cycloaddition Reactions between 3-Ethoxycyclobutanones and Allylsilanes

Formal [4 + 2] cycloaddition between various 3-ethoxycyclobutanones and allyltrialkylsilanes proceeded to give 3-ethoxy-5-[(trialkylsilyl)m-ethyl]cyclohexan-1-ones by catalysis with tin(VI) chloride. The use of allyl-tert-butyldiphenylsilane induced 1,5-hydride transfer, which gave 2-[3(tert-butyldiphenylsilyl)propyl]-6-methyltetrahydro-4-pyrones.