A method for the one-pot synthesis of phenothiazines from benzothiazoles and aryl ortho-dihalides was explored. Preliminary work on the mechanism of the reaction suggested that it follows a domino process, including the hydrolysis of benzothiazoles followed by C–S coupling and C–N coupling. The low loading of the catalyst system (5 mol-% for both copper and ligand), the mild experimental conditions (90 °C, 12 h), and the use of a green reaction medium make this synthesis very attractive to academia and industry.

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.

The C–N coupling between nucleophiles and aryl chlorides, which are less expensive, less reactive, and more abundant than their bromide and iodide counterparts, is challenging but of great interest for industrial applications. An oxalyldihydrazide/hexane-2,5-dione (100–150 mol-%)/CuO system was found to enable the reaction of a wide range of nucleophiles with a variety of aryl chlorides in water for the first time.

A series of N²,N²′-disubstituted oxalic acid bishydrazides were synthesized. Some, for example, N²,N²′-di-1-(4-methoxyphenyl)-ethanyloxylic-(bishydrazide), are novel and effective ligands for copper-catalyzed Ullmann-type CN coupling reaction in water. A variety of amines could be effectively N-arylated with aryl halides under both microwave irradiation and conventional heating (even at 30 °C) with good to excellent yields. Copyright © 2011 John Wiley & Sons, Ltd.

Pyrrole-2-carbohydrazides were synthesized and found to be novel and efficient ligands for the Cu-catalyzed amination of aryl halides with amines in pure water with high yields. A variety of aryl bromides or iodides could be aminated, promoted by the CuI/N′-phenyl-1H-pyrrole-2-carbohydrazide (L13) system, under microwave irradiation or conventional heating without the protection by an inert gas.

The N²,N²′-diisopropyloxalohydrazide/CuO system efficiently catalyzed the direct amination of aryl bromides andiodides with aqueous ammonia in water at 60 °C in 24 h or at 120 °C in only 20–30 min. Both activated and unactivated aryl and heteroaryl bromides and iodides were readily aminated in good to excellent yields.

A novel three-component catalyst CuO/oxalyldihydrazide/hexane-2,5-dione was a very convenient, economic, and effective catalytic system for the Ullmann-type C–N coupling reaction in water. Both aryl bromides and aryl iodides could be aminated by a variety of amines even at room temperature or with heating to afford very good isolated yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

An environmentally friendly Pd/C–PEG–H₂O system was developed for the cyanation of aryl halides under microwave irradiation. A wide range of aryl bromides, iodides, and some activated chlorides were demonstrated to be cyanated smoothly by using nontoxic K₄[Fe(CN)₆]·3H₂O as the cyanide source. There is no phosphorus- or nitrogen-containing ligand or solvent involved. Moreover, this reaction can becarried out without the protection of inert atmosphere. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)