Amination of Aryl Halides by Using an Environmentally Benign, Recyclable Copper Catalyst

Abstract

The combination of CuSO4 with naturally occurring sucrose in a biodegradable aqueous solution of PEG‐200 has been confirmed as a novel, recyclable, and environmentally benign homogeneous catalyst system for the direct amination of aryl halides with NH3·H2O. Electron‐rich, electron‐poor, and even ortho‐substituted aryl bromides and iodides could be aminated to provide the desired primary arylamines in high yields at 90 °C without the need of an inert atmosphere.

Copper-Mediated C–X Functionalization of Aryl Halides

“…For example, Chen and co-workers conducted CuI-catalyzed amination of aryl iodides/bromides with aqueous ammonia in 2:1 PEG-400/water solvent under ligand-free conditions . In a similar study, Wan and co-workers employed a 1:1 PEG-200/water solvent system for performing amination in the presence of a catalyst system comprising of CuSO 4 and sucrose . It is quite remarkable that the use of other ligands like glucose, fructose, glucose/fructose, maltose, starch, and cellulose gave very poor results.…”

“…199 In a similar study, Wan and co-workers employed a 1:1 PEG-200/water solvent system for performing amination in the presence of a catalyst system comprising of CuSO 4 and sucrose. 200 It is quite remarkable that the use of other ligands like glucose, fructose, glucose/fructose, maltose, starch, and cellulose gave very poor results. Interestingly, the ratio of the main copper 2p 3/2 peak to the shakeup peak in the XPS spectrum of the reaction conducted in combination with both glucose and fructose as ligand indicated that Cu(II) was partially converted into Cu(I) in the glucose/fructose system.…”

Copper-catalyzed N-arylation of heterocycles in ethylene glycol medium

“…Alteration of the molar ratio of imidazole to iodobenzene (entries [13][14] or decreasing the amount of the base (entry 15) only led to lower yields of the product. Replacing NaOH with other bases such as K 3 PO 4 or Cs 2 CO 3 , which are more common in Cucatalyzed reactions, did not improve the results (entries [16][17]. We next studied the generality of the procedure by applying the optimized conditions (Table 1, entry 10 for ArI and entry 11 for ArBr) to the reactions of some other nitrogen-heterocycles with di erent aryl halides.…”

“…In this regard, these solvents have been used in Cucatalyzed Ullmann-type C-N couplings. For instance, Huang reported amination of aryl iodides and bromides with aqueous ammonia using CuSO 4 , Cs 2 CO 3 , and sucrose as the ligand in PEG-200/water (1:1) [16]. Colasino and coworkers reported N-arylation of indole and benzimidazole in PEG-3400 under microwave irradiation at 150 C. They used 10 mol% of nano-sized Cu 2 O and two equivalents of Cs 2 CO 3 as the base [17].…”

Transition-Metal-Catalyzed Monoarylation of Ammonia

“…Additionally, the group of Wan introduced the use of sucrose L15 at a high loading (50 mol %) in conjunction with copper­(II) sulfate (20 mol %). Aryl iodides and bromides have been converted into their corresponding anilines in generally very good yield, and the reactions were conducted in water and polyethylene glycol (PEG-200) at 90 °C.…”