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Cobalt‐Catalyzed Annulation of Salicylaldehydes and Alkynes to Form Chromones and 4‐Chromanones
Author(s) -
Yang Junfeng,
Yoshikai Naohiko
Publication year - 2016
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201510999
Subject(s) - annulation , chemistry , chromone , alkyne , rhodium , salicylaldehyde , catalysis , aldehyde , medicinal chemistry , organic chemistry , stereochemistry , combinatorial chemistry , schiff base
A unique cobalt(I)–diphosphine catalytic system has been identified for the coupling of salicylaldehyde (SA) and an internal alkyne affording a dehydrogenative annulation product (chromone) or a reductive annulation product (4‐chromanone) depending on the alkyne substituents. Distinct from related rhodium(I)‐ and rhodium(III)‐catalyzed reactions of SA and alkynes, these annulation reactions feature aldehyde C−H oxidative addition of SA and subsequent hydrometalation of the C=O bond of another SA molecule as common key steps. The reductive annulation to 4‐chromanones also involves the action of Zn as a stoichiometric reductant. In addition to these mechanistic features, the Co I catalysis described herein is complementary to the Rh I ‐ and Rh III ‐catalyzed reactions of SA and internal alkynes, particularly in the context of chromone synthesis.