In 1901, F. Ullmann reported a new coupling reaction for the formation of sp²C-sp²C bond between two molecules of aryl iodide. In 1903, another paper of the N-arylation of aniline with aryl iodide was published. In 1905, the O-arylation of aryl bromide with the potassium salt of phenol was disclosed. These reactions, one coupling reaction and two condensations (or cross coupling reactions) played great roles in the development of aromatic chemistry during the turning from 19^th to 20^th century, especially in the field of dyestuff industry. Despite of these applications, the very harsh reaction condition, high temperature (~200℃) for long reaction time(one or two days) of the classical reaction of Ullmann condensation usually limited their applications.
By the efforts of several chemists in the end of last century, the acceleration effect of the Cu catalyzed Ullmann condensation by compounds with certain structure units or ligands was found. Thereafter, a surge of research interest was directed to this reaction. In this paper, the selection of various types of ligands, especially the oxalyldiamide type, the consideration of bases to be used especially the organic ionic bases, the immobilization of cooper sources and ligands and the green chemistry in Ullmann condensation are reviewed.
In 2004, Irina Beletskaya queried incisively and adequately a question:Is this a renaissance? Or "In the field of metal catalyzed cross coupling reactions, is the copper catalyzed reaction already a strong competitor to the palladium catalyzed reaction?" Beletskaya pointed out profoundly the five major drawbacks of copper catalyzed reaction. After more than ten years oxtensive investigation, a clear cut answer to this question was made as a result of several hundreds research papers dealing with the Ullmann cross coupling reactions.
Contents
1 Historical review
1.1 Name and scope of ullmann reaction
1.1.1 Ullmann reaction or ullmann coupling reaction
1.1.2 Ullmann condensation
1.2 Merits of Fritz ullmann
1.3 The follow-up achievements
2 The improvements of Ullmann condensation:the ligand accelerated Ullmann condensation
2.1 Acceleration effect by amino-acids
2.2 N, N-bidentate ligands——the phenanthrolines
2.3 N, N-bidentate ligands——the 1,2-diamines
2.4 O, O-bidentate ligands
2.5 O, N-bidentate ligands
2.5.1 Salicyl type-N, O-ligands and a tetra-dentate schiff base ligand
2.5.2 Amino alcohol ligands
2.5.3 The other O,N-bidentate ligands
2.6 Phosphorous containing ligands
2.7 The ligands used in the direct hydroxylation and direct amination of aryl Halides.
2.8 Is ligand necessary or is ullmann condensation really a "ligand accelerated catalysis"?
3 The improvements of Ullmann condensation by parameters other than ligands
3.1 The modification and loading of copper sources
3.2 The consideration of bases used
3.3 The technologies of micro-wave and supersonic used in the acceleration of rates of Ullmann condensations
3.4 The selection of solvent
4 The question of Irina Beletskaya
4.1 Five major points of Beletskaya's question
4.2 The re-examination of the cu-catalyzed Ullmann condensation after the query by Beletskaya
4.2.1 To moderate the reaction condition
4.2.2 To reduce the amounts of catalyst and ligands used
4.2.3 To make the reaction to be sustainable
4.3 The discovery of excellent ligands type——the oxalyl diamides
4.3.1 Breakthrough——the use of aryl chlorides
4.3.2 Broadening the scope of using aryl chlorides
4.3.3 The reduction of amounts of catalyst with oxalyl diamide
4.4 A difficult target for Ullmann condensation——the N-arylation of imidazole
4.5 Answer to the question of Beletskaya
4.5.1 Practical application of Ullmann condensation
4.5.2 The reduction of amounts of catalyst used
4.5.3 The use of aryl chloride
4.5.4 Tosylate or triflate as leaving group.
4.5.5 The advancement of green chemistry in Ullmann condensation
4.5.5.1 The reusable catalytic system
4.5.5.2 The use of water as solvent
4.6 Concluding remarks
5 Acknowledgements

Graphene/polyaniline nanocomposites have attracted tremendous attention of the researchers because of their significant potential in the energy storage filed, especially supercapacitors. Polyaniline(PANI)is one of ideal electrode materials, due to high theoretical specific capacity and facile synthesis. However, its drawback is poor cycling life. Graphene(GN)possesses a high theoretical specific surface area and composites of polyaniline with graphene derivatives are used to acquire excellent electrochemical capacitive properties on account of the synergistic effect between the two components. In this feature article, new research results and important advances over the past few years on the synthesis of graphene-polyaniline based nanocomposite for electrochemical supercapacitors are reviewed. And we discuss how to improve the structure and performance of electrodes. In the meantime, the application of electrode materials blended with graphene-polyaniline for organic supercapacitors is introduced. Eventually, the application prospects of graphene-polyaniline nanocomposites are briefly described. The progress of graphene/polyaniline nanocomposites in the fields of supercapacitor depends on the appropriate microstructure design of the composites. The construction of an ideal 3D porous structure is one of research interests which is used to avoid the expansion and contraction of polyaniline. Furthermore, it is still difficult to find the balance between the performance and functionalization of graphene while improving the weak interfacial interaction between graphene and polyaniline. PANI-based nanocomposites with excellent mechanical properties can also play a vital role in the study of flexible quasi-solid-state supercapacitors.
Contents
1 Introduction
2 Preparation of graphene/polyaniline nanocomposites
2.1 In-situ chemical oxidative polymerization
2.2 Electro-polymerization
2.3 Interfacial polymerization
2.4 Solution mixing
2.5 LBL self-assembled
3 Structural optimization of graphene/polyaniline nanocomposites
3.1 Microstructure control of polyaniline
3.2 Composite film
3.3 3D hierarchical structure
4 Application of graphene-polyaniline nanocomposites for organic supercapacitors
5 Conclusion and outlook