CuI/Oxalamide Catalyzed Couplings of (Hetero)aryl Chlorides and Phenols for Diaryl Ether Formation

Abstract

Couplings between (hetero)aryl chlorides and phenols can be effectively promoted by CuI in combination with an N-aryl-N'-alkyl-substituted oxalamide ligand to proceed smoothly at 120 °C. For this process, N-aryl-N'-alkyl-substituted oxalamides are more effective ligands than bis(N-aryl)-substituted oxalamides. A wide range of electron-rich and electron-poor aryl and heteroaryl chlorides gave the corresponding coupling products in good yields. Satisfactory conversions were achieved with electron-rich phenols as well as a limited range of electron-poor phenols. Catalyst and ligand loadings as low as 1.5 mol % are sufficient for the scaled-up variants of some of these reactions.

Copper(I) Oxide/N,N′‐Bis[(2‐furyl)methyl]oxalamide‐Catalyzed Coupling of (Hetero)aryl Halides and Nitrogen Heterocycles at Low Catalytic Loading

“…To initiate our studies, 4‐bromoanisole ( 1a ) and indole ( 2b ) were selected as model substrates, and 2 mol% Cu 2 O and ligands were used to explore the optimized conditions. As shown in Table , we initially tried PMPBO ( L1 ) as the ligand, which has shown excellent ability in our previous studies on coupling with phenols . The desired product could be obtained when the coupling was carried out in DMSO at 120 °C, but yield was only 30% because of poor conversion (entry 1).…”

Para‐Selective C−H Thioetherification

“…GC/MS analyses were performed on a GC/MS analysis on Agilent Technologies 5977A GC equipped with Agilent 7890B MS. High‐resolution mass spectra were carried out on a Jeol JMS‐HX 110 spectrometer by the services at the National Chung Hsing University. Ligand L was prepared following the literature procedure …”

Ausgewählte Kupfer‐katalysierte Reaktionen für die Bildung von C‐N‐, C‐O‐, C‐S‐ und C‐C‐Bindungen

“…In Verbindung mit ihrer früheren Untersuchung zur Verwendung von Oxalsäurediamiden als Liganden haben Ma und Mitarbeiter eine Reihe von Liganden für die CuI‐katalysierte Kupplung von Arylchloriden mit Phenolen untersucht und das N‐Aryl‐N′‐alkyl‐substituierte Oxalsäurediamid L30 als die beste Wahl identifiziert. Durch den Einsatz dieses Liganden konnte eine Vielzahl von (Hetero)Arylchloriden und Phenolen bei 120 °C mit nur 5 Mol‐% CuI und Ligand gekuppelt werden (Schema ) . Bei einigen schwierigen Substraten (sterisch anspruchsvolle Arylchloride und Phenole sowie elektronenarme Phenolen) musste die Katalysatormenge auf 10 Mol‐% erhöht werden, um einen vollständigen Umsatz zu erzielen.…”