Stereodivergent assembly of δ-valerolactones with an azaarene-containing quaternary stereocenter enabled by Cu/Ru relay catalysis

Abstract

Developing methodologies for the expedient construction of biologically important δ-valerolactones bearing a privileged azaarene moiety and a sterically congested all-carbon quaternary stereocenter is important and full of challenges. We present herein a novel multicatalytic strategy for the stereodivergent synthesis of highly functionalized chiral δ-valerolactones bearing 1,4-nonadjacent quaternary/tertiary stereocenters by orthogonally merging borrowing hydrogen and Michael addition between α-azaaryl acetates and allylic alcohols followed by lactonization in a one-pot manner. Enabled by Cu/Ru relay catalysis, this cascade protocol offers the advantages of atom/step economy, redox-neutrality, mild reaction conditions, and broad substrate tolerance. Scale-up experiments and synthetic transformations further demonstrated the potential for synthetic applications. Mechanistic experiments support the envisioned bimetallic relay catalytic mechanism, and the key role of Cs₂CO₃ in promoting lactonization was also revealed.