Ullmann Diaryl Ether Synthesis: Rate Acceleration by 2,2,6,6-Tetramethylheptane-3,5-dione

Abstract

[reaction: see text]. In the copper salt catalyzed ether formation from aryl bromides or iodides and phenols, 2,2,6,6-tetramethylheptane-3,5-dione (TMHD) was found to greatly accelerate the ordinarily difficult reaction, making it occur under more moderate temperatures and reaction times. A series of aryl halides and phenols were shown to form ethers in NMP as the solvent, cesium carbonate as the base, and CuCl and TMHD as the catalysts. The reaction was shown to tolerate electron-rich aryl bromides and electron-neutral phenols.

Modern Synthetic Methods for Copper‐Mediated C(aryl)O, C(aryl)N, and C(aryl)S Bond Formation

“…(30)]. [86] The reason behind the accelerating effect of this ligand is still unclear, but interestingly this ligand works best with Cs 2 CO 3 , and no accelerating effect was observed with other bases. The optimum amount of TMHD was found to be 25 mol %.…”

Copper(I) Phenoxide Complexes in the Etherification of Aryl Halides

“…of such ligands include phenanthrolines, [3,4] N,N-dimethyl glycine, [5] various pyridine derivatives, [6] β-diketones, [7] and 1,1,1-tris(hydroxymethyl)ethane. [8] Despite the progress toward improving the scope and developing milder reaction conditions for the coupling of aryl halides with phenoxides, a mechanistic basis for the relative reactivities of different catalysts toward various C-O coupling processes has not been established.…”

“…(5) [Eq. (7)] and reaction of o-(allyloxy)iodobenzene with p-CH 3 C 6 H 4 ONa catalyzed by CuI (7) and phen [Eq. (8)] produced a mixture of the p-tolyl aryl ether 6 and phenyl allyl ether 7 as the sole products.…”

Synthesis and Analysis of Triphenylamine: A Review

“…Different ligands have been examined and among them 1, 10 phenanthroline is considered to be one of the best ligands. This method has become popular and many investigators are applying this method in their synthetic route (Gujadhur et al, 2001;Antilla et al, 2002;Buck et al, 2002;Fagan et al, 2000). Their method has many advantages: it is clean so no undesirable byproduct(s) is produced, and it also moderates the harsh condition of the Ullmann condensation reaction.…”