Recent Advancement of Ullmann Condensation Coupling Reaction in the Formation of Aryl-Oxygen (C-O) Bonding by Copper-Mediated Catalyst

Abstract

Transition metal-catalyzed chemical transformation of organic electrophiles and organometallic reagents belong to the most important cross coupling reaction in organic synthesis. The biaryl ether division is not only popular in natural products and synthetic pharmaceuticals but also widely found in many pesticides, polymers, and ligands. Copper catalyst has received great attention owing to the low toxicity and low cost. However, traditional Ullmann-type couplings suffer from limited substrate scopes and harsh reaction conditions. The introduction of homogeneous copper catalyst with presence of bidentate ligands over the past two decades has totally changed this situation as these ligands enable the reaction promoted in mild condition. The reaction scope has also been greatly expanded, rendering this copper-based cross-coupling attractive for both academia and industry. In this review, we will highlight the latest progress in the development of useful homogeneous copper catalyst with presence of ligand and heterogeneous copper catalyst in Ullmann type C-O cross-coupling reaction. Additionally, the application of Ullmann type C-O cross coupling reaction will be discussed.

Functionalization of graphene oxide with a hybrid P, N ligand for immobilizing and stabilizing economical and non-toxic nanosized CuO: an efficient, robust and reusable catalyst for the C–O coupling reaction inO-arylation of phenol

“…The O -arylation reaction of phenol is a valuable process in synthetic organic chemistry and also in the preparation of many industrially important products. 57–59 The GO–PN–CuO nanocatalyst offers a wide substrate scope in the C–O coupling of phenol or its derivative with various substituted aryl chlorides and bromides at a very low Cu loading of 2.25 mol%, determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Preliminary experiments were carried out using 4-bromobenzaldehyde and phenol for optimizing the reaction conditions (Table 1) including solvents, bases, time and catalysts.…”

“…Diaryl ethers and their derivatives are very important structural motifs as they have widespread applications in pharmaceuticals, polymer industries, biologically active natural products and materials science. 57,58 Generally, diaryl ethers are prepared using copper-mediated Ullmann coupling which is a nucleophilic substitution reaction of phenol molecules with aryl halides. This method requires harsh reaction conditions such as a high temperature (>200 °C), excessive use of phenol, a long reaction time and use of a stoichiometric amount of copper.…”

New Scalable Synthetic Routes to ELQ-300, ELQ-316, and Other Antiparasitic Quinolones

“…The first step of the synthesis of diaryl ether 12 is an Ullmann reaction. 30 The copper-mediated coupling of 4-trifluoromethoxyphenol 3 and ethyl 2-(4-bromophenyl)acetate 11 with copper(I) chloride (CuCl), N,N-dimethylglycine (DMG) as a copper(I) chloride chelator, and potassium carbonate (K 2 CO 3 ) in DMF at 160 °C for 90 min afforded the diaryl ether 12 (Scheme 3). 31,32 The reaction was monitored by GC−MS and was determined to be complete when 11 was consumed.…”

Organosulphur and organoselenium compounds as emerging building blocks for catalytic systems forO-arylation of phenols, a C–O coupling reaction

“…22 The development of new synthesis methods for the preparation of diaryl ether and the quest to improve existing ones is an interesting research area for many chemists across the globe. 21 Commonly used methodologies for the generation of the diaryl ether moiety in molecules include (i) bimolecular dehydration, 23 (ii) Williamson ether synthesis, 24 and (iii) transition metal-catalysed reactions [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] such as Ullmann ether synthesis and Buchwald's palladium-catalysed ether synthesis. Bimolecular dehydration is used commercially to produce diethyl ether.…”

“…Nowadays, cross-coupling reactions are used as an effective and easy tool for generating carbon-carbon and carbonheteroatom bonds. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] Transition metals (TM) are used for the catalysis of such reactions. As there are difficulties involved in the synthesis of aryl ether moieties, commonly used synthesis procedures (which involve reduction or substitution reactions) show incompatibility with many functional groups and often involve protection and deprotection steps.…”