DDQ-Promoted Benzylic/Allylic sp³ C–H Activation for the Stereoselective Intramolecular C–N Bond Formation: Applications to the Total Synthesis of (−)-Codonopsinine, (+)-5-<i>epi</i>-Codonopsinine, (+)-Radicamine B, and (−)-Codonopsinol

Abstract

This is the first report on an intramolecular C-N bond formation of an amide-tethered benzylic/allylic system using DDQ under neutral conditions which has been successfully applied to the total synthesis of naturally occurring pyrolidine alkaloids. The key steps for the synthesis of corresponding precursors involve Julia-Kociensky olefination/cross-metathesis and dihydroxylation reactions, and this methodology is also extended to the ω-unsaturated N-sulfanilamide to furnish piperidines.