Mild Ullmann‐Type Biaryl Ether Formation Reaction by Combination of ortho‐Substituent and Ligand Effects

Abstract

An important position: A strong ortho‐substituent effect caused by NHCOR groups in 2‐haloacetanilides in combination with the ligand effect greatly promotes an Ullmann‐type biaryl formation reaction that takes place at room temperature.

Synthesis of 1,2‐Disubstituted Benzimidazoles by a Cu‐Catalyzed Cascade Aryl Amination/Condensation Process

“…However, the relatively low reaction temperature [9f, h] required for the coupling with 2-iodoacetanilide indicates that an ortho-substituent effect from the HNCOCH 3 group remained influential during the course of the reaction. Similar results were obtained when other iodides that contain aliphatic and aromatic amido groups were used (Table 1, entries [11][12][13][14][15][16][17], which indicates that the ortho-substituent effect is not limited to the HNCOCF 3 group and that variation at the 2-position of the benzimidazoles is possible by using this method. For the condensation/cyclization reaction, treatment of the coupling-reaction mixture with HOAc generally gave better results than direct heating (Table 1, entries 9-16).…”

“…[10] During studies on the CuI-catalyzed assembly of diaryl ethers using amino acids as ligands we discovered that there is an ortho-substituent effect directed by NHCOR groups in Ullmann-type C À O bond formations. [11] Further explorations revealed that the same effect exists in the coupling of aryl halides with activated methylene compounds. [12] We were interested in whether this effect could promote aryl amination to afford ortho-aminoanilides at low reaction temperatures, which in turn would provide 1,2-disubstituted benzimidazoles through an intramolecular condensation.…”

Transition‐Metal‐Free Intramolecular Ullmann‐Type O‐Arylation: Synthesis of Chromone Derivatives

“…[5p] Palladium-or copper-catalyzed intramolecular O-arylations have attracted much attention, and some oxygen heterocycles were constructed with the Ullmann-type O-arylation strategy, [6] for example copper-catalyzed synthesis of substituted 4H-1-benzopyrans (Scheme 1 b),…”

CuBr/N,N‐Dimethylglycine‐Catalyzed Coupling Reaction of 2‐Chlorotrifluoroacetanilides with Phenols at Mild Conditions

“…Generally, both electron-rich and electron-deficient phenols were compatible with these reaction conditions, delivering the corresponding diaryl ethers with good to excellent yields (Entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Noteworthy is that some sterically hindered phenols, such as 2-substituted phenols and 2,4,6-trimethylphenol, also worked well to provide 3k-3n in about 70% yield (Entries 10-13).…”

“…We have discovered that there is an ortho-substituent effect directed by amido groups in copper-catalyzed diaryl ether formation 8 and other related coupling reactions. 9 In our previous reports, only aryl bromides and iodides were examined.…”