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Capturing Elusive Cobaltacycle Intermediates: A Real‐Time Snapshot of the Cp*Co III ‐Catalyzed Oxidative Alkyne Annulation
Author(s) -
SanjoséOrduna Jesús,
Gallego Daniel,
GarciaRoca Alèria,
Martin Eddy,
BenetBuchholz Jordi,
PérezTemprano Mónica H.
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201704744
Subject(s) - alkyne , annulation , catalysis , chemistry , combinatorial chemistry , oxidative phosphorylation , reactive intermediate , oxidative addition , ligand (biochemistry) , stereochemistry , photochemistry , medicinal chemistry , organic chemistry , receptor , biochemistry
Despite Cp*Co III catalysts having emerged as a very attractive alternative to noble transition metals for the construction of heterocyclic scaffolds through C−H activation, the structure of the reactive species remains uncertain. Herein, we report the identification and unambiguous characterization of two long‐sought cyclometalated Cp*Co III complexes that have been proposed as key intermediates in C−H functionalization reactions. The addition of MeCN as a stabilizing ligand plays a crucial role, allowing the access to otherwise highly reactive species. Mechanistic investigations demonstrate the intermediacy of these species in oxidative annulations with alkynes, including the direct observation, under catalytic conditions, of a previously elusive post‐migratory insertion seven‐membered cobaltacycle.