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Cobalt‐Catalyzed Formal [4+2] Cycloaddition of α,α′‐Dichloro‐ ortho ‐Xylenes with Alkynes
Author(s) -
Komeyama Kimihiro,
Okamoto Yuji,
Takaki Ken
Publication year - 2014
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.201406807
Subject(s) - cycloaddition , cobalt , catalysis , alkyne , substrate (aquarium) , chemistry , conjugated system , transformation (genetics) , combinatorial chemistry , organic chemistry , biochemistry , oceanography , polymer , gene , geology
A formal [4+2] cycloaddition of α,α′‐dichloro‐ ortho ‐xylenes with various alkynes has been developed using a low‐valent cobalt catalyst. The transformation has a wide substrate scope and high functional‐group tolerance and led to 1,4‐dihydronaphthalenes. The formed cycloadducts were easily aromatized with MnO 2 under air. A mechanistic investigation suggests that the transformation proceeds through a benzyl cobaltation of alkyne, not the classical Diels–Alder reaction of ortho ‐quinodimethanes. This methodology provides a straightforward and streamlined access to linearly expanded π‐conjugated aromatics.