Molecular Formula
C21H18N2O2
Relative Density
1.219±0.06
General Description
PPBO (N-(2-phenylphenyl)-N′-benzyl oxalamide) is a highly effective oxalamide ligand that allows for the copper-catalyzed synthesis of diaryl ethers at low catalyst loadings. This ligand is remarkable for its performance in the cross-coupling of aryl iodides with phenols, delivering the coupling products with exceptional efficiency. Compared to structurally similar oxalamide ligands, PPBO features a simplified synthetic pathway and demonstrates superior catalytic performance.
Application
PPBO enables the synthesis of a wide range of diaryl ethers from aryl iodides and phenols. It has a broad substrate scope, efficiently coupling electron-rich, electron-poor, and ortho-substituted aryl iodides with various phenols, including naphthols and heteroaromatic alcohols. These characteristics make PPBO an attractive option for industrial applications in the synthesis of diaryl ethers.
PPBO facilitates Cu-catalyzed diaryl ether formation at unprecedentedly low loadings. Only 0.1 mol % CuI and 0.1 mol % PPBO in MeCN at 90℃ resulted in 92 % yield in the model coupling of 4-iodotoluene with phenol.
This CuI/PPBO system tolerates electron-rich and electron-poor aryl iodides, ortho-substituted partners, and a wide range of phenols including naphthols, amino-phenols and heteroaromatic alcohols, furnishing 26 examples in 72-96 % yield. Heteroaryl iodides (pyridine, quinoline, indole, benzothiophene, benzofuran, thiophene, pyrimidine, quinoxaline) couple equally well, providing medicinally relevant scaffolds. Mechanistically, the ligand is thought to chelate Cu through its two amide carbonyls, stabilising a monomeric Cu(I) centre and accelerating reductive elimination.
Fig. 1 CuI/PPBO catalyzed coupling of (Hetero)aryl Iodides Bromides with Phenols. (Zhai Y.; et al. 2017)
References
- Zhai Y, et al. Copper-catalyzed diaryl ether formation from (hetero) aryl halides at low catalytic loadings. The Journal of Organic Chemistry, 2017, 82(9): 4964-4969.
What is the PPBO ligand used for?
PPBO facilitates Cu-catalyzed diaryl ether synthesis from aryl iodides at record-low loadings.
What are the main advantages of PPBO?
Low loading, high yields and a broad substrate scope.
What purity options are available for PPBO?
Various purity grades are available. Please contact us for specifications.
Can PPBO be used in parallel synthesis?
Yes, its simplicity makes it ideal for parallel and large-scale synthesis.
Why choose PPBO for diaryl ether formation?
PPBO provides record efficiency, broad scope, and practical advantages.
