Substitution-Dependent Synthesis of Fused and Bridged γ-Butyrolactones via Tandem Cyclizations of Bromine-Containing Epoxides

We described two substitution-dependent tandem reactions of bromine-containing epoxides with 1,3-dicarbonyl compounds in the presence of a Lewis acid. When the steric hindrance of the internal carbon of the epoxide ring was negligible, fused indane-γ-butyrolactones were obtained in good yields with good diastereoselectivities. As the steric hindrance of the internal carbon of the epoxide ring increased, the reaction pathway of the tandem reaction shifted, leading to the formation of bridged tetrahydronaphthalene-γ-butyrolactones in good yields.