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Updated: Jan 7, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Access to Fused Indolines with a Quaternary N,N'-Aminal Center: Aza-Wacker-Type Cyclization for a Telescoped Reaction
Sara Caselli1, Amalija Golobič2, Fabio Mantellini1
1Department of Biomolecular Sciences, Section of Chemistry and Pharmaceutical Technologies, University of Urbino "Carlo Bo", Via Ca' Le Suore, 2, 61029 Urbino, Italy.
Abstract:
A highly efficient one-pot sequence has been developed for the rapid construction of fused polycyclic indolines bearing a C2-N,N'-aminal quaternary center. The process, which employs 1,2-diaza-1,3-dienes and 2-substituted indoles as key substrates, proceeds through a Zn(II)-catalyzed Michael addition, followed by an intramolecular Cu(II)-catalyzed dearomative oxidative cyclization. This sequence enabling N-C(sp2) bond formation via formal C(sp2)-H activation, azoalkene addition, and aza-Wacker-type cyclization exhibits broad substrate tolerance and delivers unprecedented tricyclic indole architectures (namely 9a-substituted 9,9a-dihydro-1H-pyridazino[3,4-b]indoles) in good to excellent yields.
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