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

Abstract

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.

Synthesis and Structure of Four‐Coordinate Copper(II) Complexes Stabilized by β‐Ketiminato Ligands and Application in the Reverse Atom‐Transfer Radical Polymerization of Styrene

“…This is the case for a few "methanol solvates," with Cu-O distances to the axially bonded MeOH ligand as small as 2.27 Å. [21][22][23] For another three compounds, the structure was described as mononuclear but it is in fact halidebridged dinuclear, just like 1, with "loose" Cu-X distances of 2.61 [24] and 2.84 Å [25] (X = Cl), or 3.09 Å [26] (X = Br). In other cases, although axial donor atoms are too far away for detection as bonding interactions (the distance is longer than the sum of van der Waals radii), the donor atom (Cl but sometimes also O) is correctly positioned to provide some axial electron density to the Cu center in 2D or 3D packing arrangements.…”

Spectroscopic and Computational Study on New Blue Emitting ReL(CO)3Cl Complexes Containing Pyridylimidazo[1,5‐a]pyridine Ligands

“…The m/z scan range was 200-800. 3 Cl] (ReL2) was coated with Paratone N oil, suspended in a small fiber loop, and placed in a cooled nitrogen gas stream at 173 K on a Bruker D8 SMART APEX CCD sealed tube diffractometer with graphite monochromated Mo-K α (0.71073 Å) radiation. Data were measured by using a series of combined phi and omega scans with 10 s frame exposures and 0.3°frame widths.…”

“…The 1-pyridylimidazo [1,5-a]pyridine ligands recently received potential interest for optical applications, [1][2][3] particularly in the field of OLEDs. [4,5] This class of ligands has emission in the blue region of the visible range (450-470 nm), which is a desirable, but critical, feature in OLED technology.…”

Synthesis and Characterization of Homoleptic and Heteroleptic Cobalt, Nickel, Copper, Zinc and Cadmium Compounds with the 2‐(Tosylamino)‐N‐[2‐(tosylamino)benzylidene]aniline Ligand

“…[52] The Cu-N amide bond lengths [2.014(5) and 2.027(4) Å] are not different to those found in other pentacoordinate copper(II) complexes, [57] for example, 2.041 (5) [58] or 2.003(2) and 2.044(3) Å in the above-mentioned sulfonamide complexes. [52,56] The crystal packing in this compound is very similar to that described above for other heteroleptic complexes with 1,10-phenanthroline ligands (compounds 5 and 7).…”