Sequential C–C σ-Bond Cleavage/(sp2) C–O Bond Formation via C–H Functionalization toward Pyranoindolones Fused with Medium-Sized Rings

摘要

An atom-economical procedure for the synthesis of pyranoindolones fused with 7- or 8-membered rings has been developed. This process is realized through the sequential Cs_(2)CO_(3)-promoted C–C σ-bond cleavage of cyclic ketoesters and a ZnI_(2)-mediated selective C–H/O–H coupling reaction. Two of the C–C σ-bonds are cleaved and one of the sp~(2) C–H bonds is functionalized during the reaction process. Easily accessible starting materials and broad substrate scope make this protocol attractive in synthetic organic chemistry.