10.1002/anie.202110901
Angewandte Chemie International Edition
COMMUNICATION
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copper acetylide A which upon oxidative addition to the N-O
bond of O-acetyl oxime 2 would furnish the Cu(III) complex B.[25]
Reductive elimination of the latter would provide ynimine 1-Cu(I)
complex which, upon ligand exchange with terminal alkyne 3,
would afford ynimine 1 with concurrent regeneration of the Cu(I)
acetylide A, completing therefore the catalytic cycle. For the
conversion of ynimine 1 to isoquinoline 4, two possible reaction
manifolds could be envisaged. Friedel-Crafts type cyclization of
the 1-Cu complex would afford intermediate C which upon
deprotonation would be converted to D (pathway a). Protonation
of D followed by aromatization would provide isoquinoline 4.
Alternatively, the 1-Cu complex could be in equilibrium with
enamino-ketenimine E (pathway b). The 6-p electrocyclization of
the latter would then afford F which, after protonation and
aromatization, would be converted to product 4 with concurrent
regeneration of Cu(I) species. While both pathways might be
occurring concurrently, the fact that both (E)- and (Z)-ynimines
cyclized to isoquinolines and that the electron-poor arene
participated in the cyclization (cf Scheme 3, 4af/4af') indicated
that the latter mechanistic manifold might be operational.
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[5+1]
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Acknowledgements
We thank EPFL (Switzerland), Swiss National Science
Foundation (SNSF 200021-178846/1) for financial supports. Dr.
R. O. Torres-Ochoa acknowledges CONACyT (México) for a
fellowship (CVU 256937). We thank Dr. F.-T. Farzaneh and Dr.
Rosario Scopelliti for the X-ray structural analysis of compound
1q, and 1u.
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data are provided free of charge by the joint Cambridge
Crystallographic Data Centre and Fachinformationszentrum Karlsruhe
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Conflict of Interest
The authors declare no conflict of interest.
Keywords: Cross coupling • ynimine • heterocycle •
homogeneous catalysis • domino
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