Synthesis of [4.6] spirocarbocycles: a base-promoted ring-expansion and subsequent I2-mediated regioselective spirocyclization protocol

Abstract

An efficient protocol for the synthesis of [4.6] spirocarbocycles has been developed. This process is realized through the sequential K₂CO₃-promoted C–C σ-bond cleavage of cyclic ketoesters and an I₂-mediated selective 5-exo spirocyclization reaction at room temperature. Atom economy, C–C σ bond cleavage, regioselective spirocyclization, and mild and transition-metal-free reaction conditions are the advantages of this procedure.