Diastereoselective Synthesis of Spirocyclic Dihydrofurans and 1‐Oxaspiro[4.5]decan‐6‐one Derivatives from Norbornyl α‐Diketones

Abstract

A diastereoselective zinc‐mediated propargylation of non‐enolizable norbornyl α‐diketones and an efficient AgI‐catalyzed cycloisomerization of the resulting α‐keto homopropargyl alcohols with terminal alkynes leading to spirocyclic dihydrofurans have been reported. The dihydrofurans obtained were subjected to hydrogenation to afford spiro tetrahydrofuran derivatives in nearly quantitative yields (98–99 %). Eventually, the prepared α‐spiro tetrahydrofuran norbornyl monoketones were utilized as precursors for acid‐mediated Grob‐type fragmentation reactions and converted into 1‐oxaspiro[4.5]decan‐6‐one derivatives by treatment with p‐toluenesulfonic acid.