Use of Acylhydrazine‐ and Acylhydrazone‐Type Ligands to Promote CuI‐Catalyzed C–N Cross‐Coupling Reactions of Aryl Bromides with N‐Heterocycles

Abstract

A series of ten acylhydrazine-and acylhydrazone-type ligands were designed and synthesized. Their electronic and steric properties were easily modified and tuned by varying the substituents in the vicinity of the acylhydrazine and acylhydrazone units. The effect of ligands on the catalytic

Nucleophilic Aromatic Substitution

“…Further treatment with butyl lithium results in lithium−bromine exchange followed by intramolecular substitution of the 3-fluorine to give the cyclized product (55). 140 Reaction at the amino group is enhanced in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO), which favours formation of the anionic intermediate (57). 139 There has been a detailed kinetic and computational study of the substitution of fluorine at the 6-position of 2,5,6-trifluoronicotinonitrile by 3-isopropoxy-1H-pyrazol-5-amine, which may react either at the primary amino group or at the nitrogens in the pyrazole ring.…”

“…51 Coupling of aryl bromides with phenols to give diaryl ethers has been achieved using a rhodium catalyst ligated with an N-heterocyclic carbene. 57 The reaction of azoles, such as indoles, with aryl halides may also be achieved using ligand-free copper(I) oxide in water; tetrabutylammonium bromide is used as a phase-transfer catalyst. 53,54 The direct amination of iodobenzene with aqueous ammonia can be achieved using a copper(I) iodide catalyst with a piperazine-based ligand; the method avoids the need for an additional base or an inert atmosphere.…”

Recent Synthetic Developments and Applications of the Ullmann Reaction. A Review

“…66 demonstrated an efficient Ullmann reaction of aryl bromides with N -heterocycles catalyzed by the combination of CuI and acylhydrazine- or acylhydrazone-type ligands. The facile access to the modifications of the acylhydrazine and acylhydrazone units allowed the optimization of catalytic activity and selectivity.…”

Chemo‐selective copper‐catalyzed C‐O coupling reactions of phenols with aryl/vinyl halides using enaminone as efficient ligand

“…Simultaneously, sustained interest in ligand design and application led to the discovery of many new ligand identities for copper‐catalyzed coupling reactions. For instance, BINAM, benzotriazole, hydroxyl quinoline, N ‐hydroxyimide, 2‐pyridinyl β‐ketones, d ‐glucosamine, 2‐pyridin‐2‐yl‐1 H –benzoimidazole and acylhydrazine‐/acylhydrazone, to name but a few, are recent examples of newly discovered practical ligands.…”