From Ring-Expansion to Ring-Contraction: Synthesis of γ-Lactones from Cyclobutanols and Relative Stability of Five- and Six-Membered Endoperoxides toward Organic Bases

Abstract Cyclobutanols undergo ring expansion with molecular oxygen in the presence of Co(acac)2 to afford 1,2-dioxane-hemiperoxyketals. In course acylation, we observed that endoperoxides rearranged into γ-lactone triethylamine. Thus, a generalization this contraction through Kornblum–DeLaMare rearrangement is here reported. Application transformation monosubstituted 1,2-dioxane derivatives also led 1,4-ketoaldehydes, proportions depending on nature substituent. These same conditions applied five-membered dioxolane analogues fragmentation instead, retro-aldol type process. This study emphasizes difference stability and 1,2-dioxolane against organic bases, 1,2-dioxolanes having proved be particularly reactive whereas 1,2-dioxanes showed relative tolerance under these conditions.