Complexes of Schiff Bases and Intermediates in the Copper-Catalyzed Oxidative Heterocyclization by Atmospheric Oxygen

After complexation with copper(II) ions, Schiff bases 1a − d may undergo an oxidative ring closure using atmospheric oxygen to give a number of imidazo[1,5-a]pyridines 2, an imidazo[1,5-a]imidazole 3 , and an imidazo[5,1-a]isochinoline 4. This ligand oxidation can be performed with catalytic amounts...

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Bibliographic Details
Published in:Inorganic chemistry 2003-12, Vol.42 (26), p.8878-8885
Main Authors: Bluhm, Martin E, Ciesielski, Michael, Görls, Helmar, Walter, Olaf, Döring, Manfred
Format: Article
Language:English
Subjects:
Catalysis
Copper - chemistry
Cyclization
Imidazoles - chemical synthesis
Oxidation-Reduction
Oxygen - chemistry
Pyridines - chemical synthesis
Schiff Bases - chemistry
X-Ray Diffraction
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Summary:After complexation with copper(II) ions, Schiff bases 1a − d may undergo an oxidative ring closure using atmospheric oxygen to give a number of imidazo[1,5-a]pyridines 2, an imidazo[1,5-a]imidazole 3 , and an imidazo[5,1-a]isochinoline 4. This ligand oxidation can be performed with catalytic amounts of copper ions in the reaction. A catalytic cycle for the copper-catalyzed oxidative heterocyclization will be presented together with isolated copper complexes of Schiff bases 1a,b and intermediates 5 and 8 that were found by X-ray structure analyses which confirm this reaction scheme.
ISSN:0020-1669
1520-510X
DOI:10.1021/ic034773a