Terpenoid Synthesis via Convergent Radical Annulation

Abstract

Abstract The development of a convergent radical annulation strategy for the synthesis of complex terpenoids from sclareolide is disclosed. This approach employs a 1,3‐diradical synthon to enable rapid C‐ring annulation through inter‐ and intramolecular radical couplings, exemplified in the concise syntheses of serratene and cyclodammarane scaffolds from a common intermediate. Key features include a rapid alternating polarity (rAP) Kolbe electrolysis for onoceradiene assembly, a Co‐electrocatalytic metal‐catalyzed hydrogen atom transfer (MHAT) 7‐ endo ‐trig cycloisomerization─the first of its kind─to form the serratene core, and a tandem Fe‐mediated reductive olefin coupling/enolate alkylation cascade─also unprecedented─to forge the [4.3.1] propellane motif of cyclodammaranes with complete diastereocontrol over three contiguous quaternary centers. These routes, completed in 5–9 steps, maximize skeletal bond‐forming efficiency, feature unique radical cascades, and highlight the advantages of radical‐based disconnections in terpenoid synthesis.