Patent Publication Number: US-2007100164-A1

Title: Arylamine processes

Description:
TECHNICAL FIELD  
      This disclosure is generally directed to processes for the synthesis of arylamine compounds, and to the use of such compounds in electrophotographic imaging members. In particular, this disclosure provides processes for the preparation of arylamine molecules by the reaction of an arylhalide such as an arylbromide with an arylamine in an ionic liquid using a catalyst such as a palladium catalyst, and where the palladium catalyst can be recycled.  
     RELATED APPLICATIONS  
      Commonly assigned, U.S. patent application Ser. No. 10/992,690 filed Nov. 22, 2004, describes a process for forming a tertiary arylamine compound, comprising reacting an arylbromide and an arylamine. For example, the application describes a process for forming N,N-diphenyl-4-aminobiphenyl, comprising reacting 4-bromobiphenyl and diphenylamine in the presence of a palladium ligated catalyst.  
      Commonly assigned, U.S. patent application Ser. No. 10/992,687 filed Nov. 22, 2004, describes a process for forming a 4-aminobiphenyl derivative arylamine compound, comprising: (i) providing a first disubstituted 4-aminobiphenyl compound; (ii) optionally formylating the first disubstituted 4-aminobiphenyl compound to form a bisformyl substituted compound, where the first disubstituted 4-aminobiphenyl compound is not a bisformyl substituted compound; (iii) acidifying the bisformyl substituted compound to convert formyl functional groups into acid functional groups to form an acidified compound; and (iv) hydrogenating the acidified compound to saturate at least one unsaturated double bonds in the acidified compound, wherein there is provided a second disubstituted 4-aminobiphenyl compound.  
      Commonly assigned, U.S. patent application Ser. No. 10/992,658 filed Nov. 22, 2004, describes a process for forming a 4-aminobiphenyl derivative arylamine compound, comprising: (i) providing an iodinated organic compound; (ii) substituting the iodinated organic compound at carboxylic acid groups thereof to provide ester protecting groups; (iii) conducting an Ullman condensation reaction to convert the product of step (ii) into an arylamine compound; and (iv) conducting a Suzuki coupling reaction to add an additional phenyl group to the arylamine compound in the 4-position relative to the nitrogen, to provide the 4-aminobiphenyl derivative arylamine compound.  
      Commonly assigned, U.S. patent application Ser. No. 11/094,683 filed Mar. 31, 2005, describes a process for forming an anhydrous alkali earth salt of a dicarboxylic acid of an arylamine compound, comprising reacting a dicarboxylic acid of an arylamine compound with an anhydrous alkali earth salt. The application also discloses a process for forming a siloxane-containing hole transport molecule, comprising: reacting a dicarboxylic acid of an arylamine compound with an anhydrous alkali earth salt to form an anhydrous dicarboxylic acid salt of the arylamine compound; and reacting the anhydrous dicarboxylic acid salt of the arylamine compound with a siloxane-containing compound.  
      Commonly assigned, U.S. patent application Ser. No. 10/998,585 filed Nov. 30, 2004, describes a silicon-containing layer for electrophotographic photoreceptors comprising: one or more siloxane-containing compound; and one or more siloxane-containing antioxidant; wherein the siloxane-containing antioxidant is at least one member selected from the group consisting of hindered phenol antioxidants, hindered amine antioxidants, thioether antioxidants and phosphite antioxidants.  
      Commonly assigned, U.S. patent application Ser. No. 11/034,713 filed Jan. 14, 2005, describes an electrophotographic photoreceptor comprising a charge generating layer, a charge transport layer, and an overcoat layer comprised of a crosslinked siloxane composite composition comprising at least one siloxane-containing compound and metal oxide particles  
      Commonly assigned, U.S. patent application Ser. No. 10/709,193 filed Apr. 20, 2004, describes a process for preparing an aryl iodide compound, comprising: reacting an aryl halide compound with a metal iodide, a metal catalyst and a catalyst coordinating ligand in at least one solvent to form an aryl iodide; and purifying the aryl iodide; wherein the solvent is heated to reflux during the reacting; wherein an aryl iodide yield of at least about 75% is obtained; and wherein the aryl iodide has a purity of at least 90%.  
      The appropriate components and process aspects of each of the foregoing, such as the arylamine precursor materials and electrophotographic imaging members, may be selected for the present disclosure in embodiments thereof. The entire disclosures of the above-mentioned applications are totally incorporated herein by reference.  
     REFERENCES  
      For example, JP-A-63-65449 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), discloses an electrophotographic photoreceptor in which fine silicone particles are added to a photosensitive layer, and also discloses that such addition of the fine silicone particles imparts lubricity to a surface of the photoreceptor.  
      Further, in forming a photosensitive layer, a method has been proposed in which a charge transport substance is dispersed in a binder polymer or a polymer precursor thereof, and then the binder polymer or the polymer precursor thereof is cured. JP-B-5-47104 (the term “JP-B” as used herein means an “examined Japanese patent publication”) and JP-B-60-22347, disclose electrophotographic photoreceptors using silicone materials as the binder polymers or the polymer precursors thereof.  
      Furthermore, in order to improve mechanical strength of the electrophotographic photoreceptor, a protective layer is formed on the surface of the photosensitive layer in some cases. A crosslinkable resin is used as a material for the protective layer in many cases. However, the protective layer formed by the crosslinkable resin acts as an insulating layer, which impairs the photoelectric characteristics of the photoreceptor. For this reason, a method of dispersing a fine conductive metal oxide powder (JP-A-57-128344) or a charge transport substance (JP-A-4-15659) in the protective layer and a method of reacting a charge transport substance having a reactive functional group with a thermoplastic resin to form the protective layer have been proposed.  
      However, even the above-mentioned conventional electrophotographic photoreceptors are not necessarily sufficient in electrophotographic characteristics and durability, particularly when they are used in combination with a charger of the contact charging system (contact charger) or a cleaning apparatus such as a cleaning blade.  
      Further, when the photoreceptor is used in combination with the contact charger and a toner obtained by chemical polymerization (polymerization toner), a surface of the photoreceptor is stained with a discharge product produced in contact charging or the polymerization toner remaining after a transport step to deteriorate image quality in some cases. Still further, the use of the cleaning blade in order to remove the discharge product adhered to the surface of the photoreceptor or the remaining toner increases friction and abrasion between the surface of the photoreceptor and the cleaning blade, resulting in a tendency to cause damage to the surface of the photoreceptor, breakage of the blade or turning up of the blade.  
      Furthermore, in producing the electrophotographic photoreceptor, in addition to improvement in electrophotographic characteristics and durability, it becomes an important problem to reduce production cost. However, in the case of the conventional electrophotographic photoreceptor, the problem is encountered that coating defects such as orange peel appearances and hard spots are liable to occur.  
      The use of silicon-containing compounds in photoreceptor layers, including in photosensitive and protective layers, has been shown to increase the mechanical lifetime of electrophotographic photoreceptors, under charging conditions and scorotron charging conditions. For example, U.S. Patent Application Publication US 2004/0086794 to Yamada et al., discloses a photoreceptor having improved mechanical strength and stain resistance.  
      However, the above-mentioned conventional electrophotographic photoreceptor is not necessarily sufficient in electrophotographic characteristics and durability, particularly when it is used in an environment of high heat and humidity.  
      Photoreceptors having low wear rates, such as those described in US 2004/0086794, also have low refresh rates. The low wear and refresh rates are a primary cause of image deletion errors, particularly under conditions of high humidity and high temperature. U.S. Pat. No. 6,730,448 B2 to Yoshino et al., addresses this issue in its disclosure of photoreceptors having some improvement in image quality, fixing ability, even in an environment of high heat and humidity. However, there still remains a need for electrophotographic photoreceptors having high mechanical strength and improved electrophotographic characteristics and improved image deletion characteristics even under conditions of high temperature and high humidity.  
      Buchwald et al. (MIT) and Hartwig et al. (Yale) have both reported over the past several years on the general versatility of palladium based catalysts for the formation of nitrogen-carbon bonds. While their work has focused on the arylation of alkylamine and alkylamides, they have reported the use of a palladium based catalyst for arylamine synthesis starting from an arylbromide or an arylchloride. See Michele C. HARRIS et al; “One-Pot Synthesis of Unsymmetrical Triarylamines from Aniline Precursors”; J.  Org. Chem . Vol. 65, pp. 5327-5333 (2000). The present disclosure adapts the procedure for the production of arylamine derivatives, specifically arylamine derivatives of 4-aminobiphenyl. More specifically, this disclosure pertains to the use of ligated palladium catalyzed production of arylamine derivatives (for example derivatives of 4-aminobiphenyl) by reaction of an arylamine (for example diphenylamine) with an arylbromide (for example 4-bromobiphenyl) in the presence of a base (for example sodium tert-butoxide) in a short period of time, in an economical way and isolatable in suitable purity as to be used as starting materials for the further synthesis of arylamine derivatives, for example, for application in electrophotographic photoreceptors or alternatively itself could be suitable for application in electrophotographic photoreceptors.  
      The disclosures of each of the foregoing patents and publications are hereby incorporated by reference herein in their entireties. The appropriate components and process aspects of the each of the foregoing patents and publications may also be selected for the present compositions and processes in embodiments thereof.  
     BACKGROUND  
      In electrophotography, an electrophotographic substrate containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging a surface of the substrate. The substrate is then exposed to a pattern of activating electromagnetic radiation, such as, for example, light. The light or other electromagnetic radiation selectively dissipates the charge in illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in non-illuminated areas of the photoconductive insulating layer. This electrostatic latent image is then developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer. The resulting visible image is then transferred from the electrophotographic substrate to a necessary member, such as, for example, an intermediate transfer member or a print substrate, such as paper. This image developing process can be repeated as many times as necessary with reusable photoconductive insulating layers.  
      In image forming apparatus such as copiers, printers and facsimiles, electrophotographic systems in which charging, exposure, development, transfer, etc. are carried out using electrophotographic photoreceptors have been widely employed. In such image forming apparatus, demands for speeding up of image formation processes, improvement in image quality, miniaturization and prolonged life of the apparatus, reduction in production cost and running cost, etc. are increasingly growing. Further, with recent advances in computers and communication technology, digital systems and color image output systems have been applied also to the image forming apparatus.  
      Electrophotographic imaging members (i.e. photoreceptors) are known. Electrophotographic imaging members are commonly used in electrophotographic processes having either a flexible belt or a rigid drum configuration. These electrophotographic imaging members sometimes comprise a photoconductive layer including a single layer or composite layers. These electrophotographic imaging members take many different forms. For example, layered photoresponsive imaging members are known in the art. U.S. Pat. No. 4,265,990 to Stolka et al., which is totally incorporated herein by reference, describes a layered photoreceptor having separate photogenerating and charge transport layers. The photogenerating layer disclosed in the 990 patent is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer. Thus, in the photoreceptors of the 990 patent, the photogenerating material generates electrons and holes when subjected to light.  
      More advanced photoconductive photoreceptors containing highly specialized component layers are also known. For example, a multilayered photoreceptor employed in electrophotographic imaging systems sometimes includes one or more of a substrate, an undercoating layer, an intermediate layer, an optional hole or charge blocking layer, a charge generating layer (including a photogenerating material in a binder) over an undercoating layer and/or a blocking layer, and a charge transport layer (including a charge transport material in a binder). Additional layers such as one or more overcoat layer or layers are also sometimes included.  
      In view of such a background, improvement in electrophotographic properties and durability, miniaturization, reduction in cost, etc., in electrophotographic photoreceptors have been studied, and electrophotographic photoreceptors using various materials have been proposed.  
     SUMMARY  
      The present disclosure addresses these and other needs, by providing a method for the production of an arylamine molecule in an ionic liquid using a suitable catalyst such as a palladium catalyst, where the palladium catalyst can be recycled. In embodiments, the disclosure provides methods for forming derivatives of compounds (such as substituted compounds), without requiring use of the basic compound itself, which may be hard to obtain or may pose environmental or health dangers. For example, the disclosure provides a process for forming an arylamine molecule that is a derivative to 4-aminobiphenyl, but the process allows its production without the use of 4-aminobiphenyl compound itself from readily available commercial materials. Generally, for the formation of derivatives of 4-aminobiphenyl, the compound 4-aminobiphenyl is itself used as a starting or raw material. However, because 4-aminobiphenyl is a known human carcinogen, its use in a manufacturing/industrial setting is not desirable.  
      The above problem has been overcome by derivatization of a diarylamine molecule (for example diphenylamine) with 4-iodobiphenyl under traditional Ullman condensation conditions. As 4-iodobiphenyl is not a commercially available material, its synthesis from biphenyl by iodoination is necessary. However, iodination of biphenyl is know to produce amounts of diiodobiphenyl and leave a residue of biphenyl in its reaction products, each of which is removed for the iodobiphenyl to be of practical use. This separation and purification of 4-iodobiphenyl is time consuming and costly, resulting in the product being an estimated  10  fold more expensive than 4-bromobiphenyl. In contrast, 4-bromobiphenyl is commercially available in purities suitable for use as a feedstock in arylamine production; however, its reactivity under standard Ullman conditions is not facile enough to allow for reaction in an economical amount of time. Therefore there is a need for a process by which 4-bromobiphenyl can be used as a feedstock for the production of arylamine derivatives, specifically arylamine derivatives of 4-aminobiphenyl.  
      In commonly assigned U.S. patent application Ser. No. 10/992,690 filed Nov. 22, 2004, described above, 4-bromobiphenyl is used as a feedstock for the production of arylamine derivatives by reacting 4-bromobiphenyl and diphenylamine in the presence of a palladium ligated catalyst. However, the palladium catalyst is expensive, and it is desired to improve the process by allowing the catalyst to be more easily recycled for future use.  
      To offset the high cost of the palladium catalyst, further improvements are desired that would allow the palladium catalyst to be recycled for use in multiple reaction cycles. One such recycling method is provided herein.  
      These and other features and advantages of various exemplary embodiments of materials, devices, systems and/or methods according to this disclosure are described in, or are apparent from, the following detailed description of the various exemplary embodiments of the methods and systems according to this disclosure.  
      In an embodiment, the present disclosure provides a process for forming a tertiary arylamine compound, comprising reacting an arylhalide such as an arylbromide and an arylamine in an ionic liquid in the presence of a catalyst, to form a reaction product. For example, the disclosure provides a process for forming N,N-diphenyl-4-aminobiphenyl, comprising reacting 4-bromobiphenyl and diphenylamine in an ionic liquid in the presence of a palladium catalyst.  
      In the case where the arylamine is used as a starting material for the further derivatization of arylamine molecules, it can be used to synthesize a compound containing siloxane groups (see, for example. Compound C in  FIG. 5 ). Such siloxane group containing compounds are useful, for example, in the preparation of siloxane containing charge transporting layers or overcoating layers for electrophotographic application.  
      In another embodiment, the present disclosure provides a process for forming a tertiary arylamine compound, comprising:  
      (a) forming a reaction medium comprising an arylbromide, an arylamine, an ionic liquid, and a catalyst;  
      (b) allowing the arylbromide and the arylamine to react in the reaction medium to form a reaction product;  
      (c) adding water and an organic solvent to the reaction product to form a triphasic system comprising a first phase comprising the tertiary arylamine and the organic solvent, a second phase comprising the catalyst and the ionic liquid; and a third phase comprising water and inorganic salts;  
      (d) separating the first phase and optionally the third phase from the second phase;  
      (e) adding additional arylbromide and arylamine to the second phase to form an additional reaction medium; and  
      (f) repeating (b) to (d) at least one additional time to form additional arylamine compounds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic cross sectional view showing an embodiment of an electrophotographic photoreceptor of the disclosure.  
       FIG. 2  is a schematic view showing an embodiment of an image forming apparatus of the disclosure.  
       FIG. 3  is a schematic view showing another embodiment of an image forming apparatus of the disclosure.  
       FIG. 4  sets forth two processes for the production of an arylamine derivative.  
       FIG. 5  sets forth a process by which a siloxane containing arylamine can be produced. 
    
    
     EMBODIMENTS  
      Production of a number of arylamine compounds, such as arylamine compounds that are useful as charge transport compounds in electrostatographic imaging devices and processes, often involves synthesis of intermediate materials, some of which generally are costly and/or time-consuming to produce, and some of which involve a multi-step process. One such intermediate product is the arylamine N,N-diphenyl-4-aminobiphenyl, which is useful as a charge transport compound in electrostatographic imaging devices and processes. Even production of this intermediate compound currently involves a long, costly process.  
      For example, N,N-diphenyl-4-aminobiphenyl has been produced by reacting 4-iodobiphenyl and diphenylamine under standard Ullman condensation conditions. However, 4-iodobiphenyl is an expensive material and is not readily available in many countries, such as the United States. While the process for producing 4-iodobiphenyl is known, it is costly and time consuming and especially time consuming to purify to a level suitable for further reaction and processes. Alternatively, the process could be conducted using 4-bromobiphenyl, which is more readily available and is 10-fold cheaper. However, the rate of reaction of arylbromides is known to be significantly slower than aryliodides under standard Ullman conditions. In fact, it has been confirmed that the reaction of diphenylamine with 4-bromobiphenyl does not produce the desired arylamine even after many days under standard Ullman conditions. Accordingly, improved processes are desired for producing arylamines, such as N,N-diphenyl-4-aminobiphenyl, and similar compounds.  
      A process for producing this and other similar intermediate products is to react an arylhalide, such as an arylbromide, and an arylamine in the presence of a suitable catalyst. This process is shown alternatively in the reaction scheme of  FIG. 4 . For example, 4-bromobiphenyl and diphenylamine can be rapidly reacted to form N,N-diphenyl-4-aminobiphenyl using palladium acetate ligated with tri-t-butylphosphine as a catalyst and sodium t-butoxide base. This reaction proceeds rapidly, in about 1.5 hours, to produce the desired N,N-diphenyl-4-aminobiphenyl. This process is described in detail in commonly assigned, U.S. patent application Ser. No. 10/992,690 filed Nov. 22, 2004. Although this process uses a costly catalyst, such as a palladium catalyst, the cost of the catalyst is offset by the cost and time savings associated with the shorter and faster process and the cheapness of 4-bromobiphenyl.  
      An alternative or improved process is now described in detail.  
      According to embodiments, an arylhalide such as an arylbromide and an arylamine are used as starting materials. Any suitable arylhalide can be used, such as arylbromides, arylchlorides, aryliodides, aryl fluorides, and the like. Likewise, any suitable arylamine can be used. The selection of specific starting arylhalide and arylamine depend, for example, upon the desired final product. For example, in embodiments, the arylamine is an arylbromide such as 4-bromobiphenyl and the arylamine is diphenylamine, which react to form the arylamine N,N-diphenyl-4-aminobiphenyl.  
      In embodiments, where an arylbromide is used, the reaction, including the starting materials and final product, can generally be represented as follows:  
                 
 
 Thus, in this embodiment, an arylbromide is reacted with a secondary arylamine to produce a tertiary arylamine. 
 
      In this reaction scheme, the arylbromide can be any suitable arylbromide, depending upon the desired final product. Thus, for example, in the above reaction scheme, the substituents R 1 , R 2 , R 3 , R 4  and R 5 , which can be the same or different, can be suitably selected to represent hydrogen, a halogen, an alkyl group having for example from 1 to about 20 carbon atoms (such as methyl, ethyl, propyl, butyl and the like), a hydrocarbon radical having for example from 1 to about 20 carbon atoms, an aryl group optionally substituted by one or more alkyl groups, an alkyl group containing a heteroatom such as oxygen, nitrogen, sulfur and the like having for example from 1 to about 20 carbon atoms, a hydrocarbon radical containing a heteroatom such as oxygen, nitrogen, sulfur and the like having for example from 1 to about 20 carbon atoms, an aryl group containing a heteroatom such as oxygen, nitrogen, sulfur and the like optionally substituted by one or more alkyl groups, and the like. In embodiments, one of R 1 , R 2 , R 3 , R 4  and R 5 , such as R 3 , represents a phenyl group and the remaining represent H atoms. Thus, in this embodiment, the arylbromide is 4-bromobiphenyl.  
      Likewise, in this reaction scheme, the arylamine can be any suitable arylamine, depending upon the desired final product. Thus, for example, in the above reaction scheme, the substituents R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , and R 15 , which can be the same or different, can be suitably selected to represent hydrogen, a halogen, an alkyl group having for example from 1 to about 20 carbon atoms (such as methyl, ethyl, propyl, butyl and the like), a hydrocarbon radical having for example from 1 to about 20 carbon atoms, an aryl group optionally substituted by one or more alkyl groups, an alkyl group containing a heteroatom such as oxygen, nitrogen, sulfur and the like having for example from 1 to about 20 carbon atoms, a hydrocarbon radical containing a heteroatom such as oxygen, nitrogen, sulfur and the like having for example from 1 to about 20 carbon atoms, an aryl group containing a heteroatom such as oxygen, nitrogen, sulfur and the like optionally substituted by one or more alkyl groups, and the like. In embodiments, each of R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , and R 15  represent H atoms. Thus, in certain embodiments, the arylamine is diphenylamine.  
      The reactants are reacted in the presence of a suitable catalyst. Although not particularly limited, suitable catalysts are those that are known or discovered to be useful for formation of nitrogen-carbon bonds. For example, suitable catalysts include palladium ligated catalysts, such as those disclosed by Buchwald et al. and Hartwig et al. (for example in Michele C. HARRIS et al; “One-Pot Synthesis of Unsymmetrical Triarylamines from Aniline Precursors”; J. Org. Chem. Vol. 65, pp. 5327-5333 (2000), the disclosure of which is totally incorporated herein by reference).  
      In embodiments, a particular suitable catalyst is a palladium acetate ligated with tri-t-butylphosphine and sodium t-butoxide base. However, it will be apparent that other ligands, such as tri- or di-substituted-phosphine ligands, could also be used to produce suitable results (from the point of view of conversion and yield), and thus would be suitable to ligate palladium or other metals and thus act to catalyze the process described in this disclosure. It will also be apparent that the use of phosphine-type ligands to ligate palladium are not the only ligate options, and other ligates are known or may become known to allow palladium to have catalytic activity under the described conditions. For example, nitrogen, oxygen or other heteroatom containing organic compounds as well as halogens are known to ligate to palladium.  
      The reaction is carried out in the presence of the catalyst, and can be conducted in batch or continuous mode. However, in embodiments, the reaction is conducted in batch mode. For example, the reaction can be carried out for a period of from about 30 minutes to about 5 hours or more, such as from about 30 minutes to about 10 or to about 15 hours, although a reaction time of from about 1 or from about 1.5 to about 2 or about 3 hours is suitable in embodiments.  
      The reaction is carried out in a suitable ionic liquid as a solvent or mixtures of ionic liquids and organic solvents such as hydrocarbons, ethers and the like. Mixtures of ionic liquids and organic solvents can be chosen so as to produce a triphasic mixture on workup of the reaction. The ionic liquid therefore enables subsequent separation and re-use of the palladium catalyst, thus providing cost reductions in the arylamine synthesis process.  
      Any suitable ionic liquid can be used as the reaction solvent. Ionic solvents, and their use as effective media for cross-coupling reactions, are disclosed in Chem. Commun., 2002, 1986-1987, and Tetrahedron Letters, 2004, 45(41), 7629-7631. For example, suitable ionic liquids include organic phosphonium halides such as organic phosphonium chlorides, imidazolium halides such as imidazolium iodides, and the like. Specific examples of suitable organic liquids include (tetradecyl)trihexyl phosphonium chloride, methoxy methyltriphenyl phosphonium chloride, 2-nitrobenzyltriphenyl phosphonium chloride, butylmethylimidazolium iodide, and the like. There can also be ionic compounds that are solids at room temperatures but melt in a range between room temperature and the temperature at which the described process is conducted, and ionic compounds that are solids at room temperature and in the presence of either organic solvents or water have a melting point that is depressed to be between room temperature and the temperature at which the described process is conducted, compounds of each type are also suitable for use in the described process. Accordingly, in embodiments, “ionic liquid” for example refers to a an ionic material that is or becomes liquid at temperatures ranging from about room temperature (about 20° C. to about 25° C.) to a reaction temperature. Typical reaction temperatures can be, for example, from about 30 to about 150° C. or more, such as from about 50 to about 125° C. or from about 75 to about 100° C. However, other reaction temperatures can be used, in embodiments.  
      Typical ionic liquids that can be utilized have an organic cation and an anion that may be either organic or inorganic. Typical organic cations are imidazolium cations, pyridinium cations, pyrrolidinium cations, tetraalkyl phosphonium cations, and tetraalkyl ammonium cations. Exemplary cations include imidazolium cations, such as 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2-dimethyl-3-propylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-methyl-3-octylimidazolium; and pyridinium cations, such as 1-butyl-4-methylpyridinium. Typical anions are methylsulfonate, trifluoromethylsulfonate, bromide, chloride, nitrate, tetrafluoroborate, hexafluorophosphate, methylsulfate, and bromotrichloroaluminate. Hydrophobic ionic liquids are disclosed, for example, in U.S. Pat. No. 5,827,602, the disclosure of which is totally incorporated herein by reference. The hydrophobic ionic liquids have non-Lewis acid-containing polyatomic anions such as bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methide, bis(pentafluoroethylsulfonyl)imide, and perfluoro-1,1-dimethylpropyl alkoxide.  
      Further examples of suitable ionic liquids include 1,3-dimethylimidazolium methylsulfate (DiMIM MeSO 4 ), 1,2-dimethyl-3-propylimidazolium tris(trifluoromethylsulfonyl)methide, 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium nitrate, 1-ethyl-3-methyl imidazolium tetrafluoroborate, 1-ethyl-3-methyl imidazolium trifluoromethylsulfonate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI Im), 1-ethyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride (BMIM Cl), 1-ethyl-2,3-dimethylimidazolium tosylate (EDiMIM TOS), 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF 6 ), 1-butyl-3-methylimidazolium diethyleneglycol monomethylether sulfate, N-propyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM BF 4 ), 1-butyl-3-methylimidazolium bromotrichloroaluminate, 1-butyl-3-methylimidazolium diethyleneglycol monomethylether sulfate (BMIM MDEGSO 4 ), 1-butyl-3-methylimidazolium phosphate, 1-butyl-3-methylimidazolium octylsulfate (BMIM OCSO 4 ), 1-butyl-2,3-dimethylimidazolium chloride, N-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-2,3-dimethylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-methyl-3-octylimidazolium chloride, 1-methyl-3-octylimidazolium diethyleneglycol monomethylether sulfate (OMIM MDEGSO 4 ), 1-methyl-3-octylimidazolium octylsulfate (OMIM OcSO 4 ), 1-methyl-3-octylimidazolium-tetrafluoroborate (OMIM BF 4 ), 1-octadecyl-3-methylimidazolium chloride, 1-butyl-4-methylpyridinium chloride, 1-butyl-4-methylpyridinium hexafluorophosphate, 1-butyl-4-methylpyridinium tetrafluoroborate, N-octyl-pyridinium tris(trifluoromethylsulfonyl)methide, N-hexyl-pyridinium tetrafluoroborate, 4-methyl-N-butyl-pyridinium chloride, N-hexyl-pyridinium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methyl-pyrrolidinium chloride, 1,1-dimethyl-pyrrolidinium tris(pentafluoroethyl)trifluorophosphate, 1-hexyl-1-methyl-pyrrolidinium dicyanamide, 1-octyl-1-methyl-pyrrolidinium chloride, tetramethyl-ammonium bis(trifluoromethyl)imide, tetrabutyl-ammonium bis(trifluoromethyl)imide, tetraethyl-ammonium tris(pentafluoroethyl)trifluorophosphate, and tetrabutyl-phosphonium tris(pentafluoroethyl)trifluorophosphate.  
      In embodiments, the ionic liquid can be used in combination with one or more conventional suitable solvent, such as an organic solvent.  
      It will also be apparent that other ionic liquids can be made by exchange reaction between a commercially available ionic liquid and a suitable salt such as an inorganic salt or an organic salt in an analogous procedure to that used to exchange either anions or cations on an anion exchange resin or cation ion exchange resin, respectively.  
      The choice of specific solvent, ionic liquid or mixture thereof can be decided based on the solubility of the starting materials, intermediates and final products, and will be readily apparent or within routine experimentation to those skilled in the art. For example, it is desired in embodiments that the starting materials such as the arylhalide, arylamine and catalyst are soluble in the ionic liquid, while the formed arylamine product is soluble in an organic solvent but is insoluble in the ionic liquid, and the catalyst remains soluble in the ionic liquid after completion of the reaction. In embodiments, “soluble” refers to, for example, the specified material being substantially soluble in the respective solvent, although complete (100%) solubility is not necessarily required. Likewise, in embodiments, “insoluble” refers to, for example, the specified material being substantially insoluble in the respective solvent, although complete (100%) insolubility is not necessarily required. Furthermore the choice of solvent, ionic liquid or mixture thereof can be decided based on the desired operating temperature range. In some embodiments; the described process may be exothermic and precautions should be taken to ensure that a mixture of ionic liquid and a suitable organic solvent is chosen that is capable of dispersing the produced heat by, for example, refluxing and cooling at such a rate so as to control the exotherm. In embodiments, a mixture of an ionic liquid and a solvent can be used, as the solvent will typically reflux whereas the ionic liquid will not. The reaction should be conducted under an atmosphere of inert gas (such as nitrogen or argon) so as to preclude deactivation of catalyst or base by oxygen or atmospheric moisture.  
      After the reaction is completed, suitable separation, filtration, and/or purification processes can be conducted, as desired to a desired purity level. For example, the desired arylamine product can be subjected to conventional organic washing steps, can be separated, can be decolorized (if necessary), treated with known absorbents (such as silica, alumina and clays, if necessary) and the like. The final product can be isolated, for example, by a suitable recrystallization procedure. The final product can also be dried, for example, by air drying, vacuum drying, or the like. All of these procedures are conventional and will be apparent to those skilled in the art.  
      However, a particular benefit of embodiments is that the desired final product and the palladium catalyst can be easily separated, such that the catalyst can be recycled and re-used. A benefit of the ionic liquid is that, once the reaction is complete, addition of water and an organic solvent causes the formation of a triphasic medium. In this triphasic medium, one phase (such as the upper organic phase) includes the desired arylamine final product; one phase (such as the middle ionic liquid phase) includes the palladium catalyst; and one phase (such as the bottom aqueous phase) includes inorganic salts and other water soluble or miscible materials such as the alcohol produced by this process. These three phases can be easily separated, so that the desired arylamine product can be isolated, and the catalyst-carrying ionic liquid phase can be re-used in a subsequent process. For example, the catalyst-carrying ionic liquid phase can be first isolated and purified, or it can be directly recharged with additional reactants to conduct a further arylamine synthesis reaction. In embodiments, the relative amounts and proportions of the three phases in the triphasic medium may vary, depending upon, for example, the specific starting materials, intermediates and final products, the specific solvent, ionic liquid or mixture thereof selected, and the like.  
      Accordingly, in embodiments, the synthesis method further comprises adding sufficient amounts of water and an organic solvent to provide a triphasic medium. Suitable organic solvents include, for example, hexane, ether, toluene, decane, other hydrocarbon solvents (either aromatic or saturated hydrocarbons), other ethers such as tetrahydrofuran, dimethoxyethane and the like and mixtures thereof.  
      After the triphasic medium is formed, at least the ionic liquid phase is removed for subsequent reuse of the entire ionic liquid phase, or at least of the catalyst contained therein. If desired, and as appropriate, the organic and aqueous phases can also be separated, and appropriately processed.  
      The arylamine produced by this process can itself be used as a final product, or it can be further processed and/or reacted to provide other compounds for their separate use. For example, the arylamine can be used itself as a charge transport material in an electrostatographic imaging member, or it can be further processed and/or reacted to provide other charge transport materials or other compounds useful in such electrostatographic imaging member. An exemplary electrostatographic imaging member will now be described in greater detail.  
      In electrophotographic photoreceptors of embodiments, the photoreceptors can include various layers such as undercoating layers; charge generating layers, charge transport layers, overcoat layers, and the like. The overcoating layers of embodiments can be a silicon overcoat layer, which can comprise one or more silicon compounds, a resin, and a charge transport molecule such as an arylamine.  
      In embodiments, the resin may be a resin soluble in a liquid component in a coating solution used for formation of a silicon overcoat layer. Such a resin soluble in the liquid component may be selected based upon the kind of liquid component. For example, if the coating solution contains an alcoholic solvent (such as methanol, ethanol or butanol), a polyvinyl acetal resin such as a polyvinyl butyral resin, a polyvinyl formal resin or a partially acetalized polyvinyl acetal resin in which butyral is partially modified with formal or acetoacetal, a polyamide resin, a cellulose resin such as ethyl cellulose and a phenol resin may be suitably chosen as the alcohol-soluble resins. These resins may be used either alone or as a combination of two or more resins. Of the above-mentioned resins, the polyvinyl acetal resin is particularly suitable in embodiments in terms of electric characteristics.  
      In embodiments, the weight-average molecular weight of the resin soluble in the liquid component may be from about 2,000 to about 1,000,000, such as from about 5,000 to about 50,000. When the average molecular weight is less than about 2,000, the effect of enhancing discharge gas resistance, mechanical strength, scratch resistance, particle dispersibility, etc., tends to become insufficient. However, when the average molecular weight exceeds about 1,000,000, the resin solubility in the coating solution decreases, and the amount of resin added to the coating solution may be limited and poor film formation in the production of the photosensitive layer may result.  
      Further, the amount of the resin soluble in the liquid component may be, in embodiments, from about 0.1 to about 15% by weight, or from about 0.5 to about 10% by weight, based on the total amount of the coating solution. When the amount added is less than 0.1% by weight, the effect of enhancing discharge gas resistance, mechanical strength, scratch resistance, particle dispersibility, etc. tends to become insufficient. However, if the amount of the resin soluble in the liquid component exceeds about 15% by weight, there is a tendency for formation of indistinct images when the electrophotographic photoreceptor of the disclosure is used at high temperature and high humidity.  
      In embodiments, for example, a “high temperature environment” or “high temperature conditions” refer to an atmosphere in which the temperature is at least about 28 to about 30° C. A “high humidity environment” or “high humidity conditions” refer to an atmosphere in which the relative humidity is at least about 75 to about 80%.  
      There is no particular limitation on the silicon compound used in embodiments of the disclosure, as long as it has at least one silicon atom. However, a compound having two or more silicon atoms in its molecule may be used in embodiments. The use of the compound having two or more silicon atoms in its molecule allows both the strength and image quality of the electrophotographic photoreceptor to be achieved at higher levels.  
      Further, in embodiments, the silicon compounds may include silane coupling agents such as a tetrafunctional alkoxysilane such as tetramethoxysilane or tetraethoxysilane; a trifunctional alkoxysilane such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, methyltrimethoxyethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, 3-(heptafluoroisopropoxy)propyltriethoxysilane, 1H,1H,2H,2H-perfluoroalkyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane or 1H,1H,2H,2H-perfluorooctyltriethoxysilane; a bifunctional alkoxysilane such as dimethyldimethoxysilane, diphenyldimethoxysilane or methylphenyldimethoxysilane; and a monofunctional alkoxysilane such as trimethylmethoxysilane. In order to improve the strength of the photosensitive layer, trifunctional alkoxysilanes and tetrafunctional alkoxysilanes may be used in embodiments, and in order to improve the flexibility and film forming properties, monofunctional alkoxysilanes and bifunctional alkoxysilanes may be used in embodiments.  
      Silicone hard coating agents containing these coupling agents can also be used in embodiments. Commercially available hard coating agents include KP-85, X-40-9740 and X-40-2239 (available from Shinetsu Silicone Co., Ltd.), and AY42-440, AY42-441 and AY49-208 (available from Toray Dow Corning Co., Ltd.).  
      In order to further improve the stain adhesion resistance and lubricity of embodiments of the electrophotographic photoreceptor, various fine particles can also be added to the silicon compound-containing layer. The fine particles may be used either alone or as a combination of two or more such fine particles. Non-limiting examples of the fine particles include fine particles containing silicon, such as fine particles containing silicon as a constituent element, and specifically include colloidal silica and fine silicone particles.  
      Colloidal silica used in embodiments as the fine particles containing silicon in the disclosure is selected from an acidic or alkaline aqueous dispersion of the fine particles having an average particle size of 1 to 100 nm, or 10 to 30 nm, and a dispersion of the fine particles in an organic solvent such as an alcohol, a ketone or an ester, and generally, commercially available particles can be used.  
      There is no particular limitation on the solid content of colloidal silica in a top surface layer of the electrophotographic photoreceptor of embodiments. However, in embodiments, colloidal silica is used within the range of from about 1 to about 50% by weight, such as from about 5 to about 30% by weight, based on the total solid content of the top surface layer, in terms of film forming properties, electric characteristics and strength.  
      The fine silicone particles used as the fine particles containing silicon in the disclosure are selected from silicone resin particles, silicone rubber particles and silica particles surface-treated with silicone, which are spherical and have an average particle size of from about 1 to 500 nm, such as from about 10 to about 100 nm, and generally, commercially available particles can be used in embodiments.  
      In embodiments, the fine silicone particles are small-sized particles that are chemically inactive and excellent in dispersibility in a resin, and further are low in content as may be necessary for obtaining sufficient characteristics. Accordingly, the surface properties of the electrophotographic photoreceptor can be improved without inhibition of the crosslinking reaction. That is to say, fine silicone particles improve the lubricity and water repellency of surfaces of electrophotographic photoreceptors where incorporated into strong crosslinked structures, which may then be able to maintain good wear resistance and stain adhesion resistance for a long period of time. The content of the fine silicone particles in the silicon compound-containing layer of embodiments may be within the range of from about 0.1 to about 20% by weight, such as from about 0.5 to about 10% by weight, based on the total-solid content of the silicon compound-containing layer.  
      Other fine particles that may be used in embodiments include fine fluorine-based particles such as ethylene tetrafluoride, ethylene trifluoride, propylene hexafluoride, vinyl fluoride and vinylidene fluoride, and semiconductive metal oxides such as ZnO—Al 2 O 3 , SnO 2 —Sb 2 O 3 , In 2 O 3 —SnO 2 , ZnO—TiO 2 , MgO—Al 2 O 3 , FeO—TiO 2 , TiO 2 , SnO 2 , In 2 O 3 , ZnO and MgO.  
      In conventional electrophotographic photoreceptors, when the above-mentioned fine particles are contained in the photosensitive layer, the compatibility of the fine particles with a charge transport substance or a binding resin may become insufficient, which causes layer separation in the photosensitive layer, and thus the formation of an opaque film. As a result, the electric characteristics have deteriorated in some cases. In contrast, the silicon compound-containing layer of embodiments (a charge transport layer in this case) may contain the resin soluble in the liquid component in the coating solution used for formation of this layer and the silicon compound, thereby improving the dispersibility of the fine particles in the silicon compound-containing layer. Accordingly, the pot life of the coating solution can be sufficiently prolonged, and it becomes possible to prevent deterioration of the electric characteristics.  
      Further, an additive such as a plasticizer, a surface modifier, an antioxidant, or an agent for preventing deterioration by light can also be used in the silicon compound-containing layer of embodiments. Non-limiting examples of plasticizers that may be used in embodiments include, for example, biphenyl, biphenyl chloride, terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenylphosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene and various fluorohydrocarbons.  
      The antioxidants may include an antioxidant having a hindered phenol, hindered amine, thioether or phosphite partial structure. This is effective for improvement of potential stability and image quality in environmental variation. The antioxidants include an antioxidant having a hindered phenol, hindered amine, thioether or phosphite partial structure. This is effective for improvement of potential stability and image quality in environmental variation. For example, the hindered phenol antioxidants include Sumilizer BHT-R, Sumilizer MDP-S, Sumilizer BBM-S, Sumilizer WX-R, Sumilizer NW, Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80, Sumilizer GM and Sumilizer GS (the above are manufactured by Sumitomo Chemical Co., Ltd.), IRGANOX 1010, IRGANOX 1035, IRGANOX 1076, IRGANOX 1098, IRGANOX 1135, IRGANOX 1141, IRGANOX 1222, IRGANOX 1330, IRGANOX 1425WLj, IRGANOX 1520Lj, IRGANOX 245, IRGANOX 259, IRGANOX 3114, IRGANOX 3790, IRGANOX 5057 and IRGANOX 565 (the above are manufactured by Ciba Specialty Chemicals), and Adecastab AO-20, Adecastab AO-30, Adecastab AO-40, Adecastab AO-50, Adecastab AO-60, Adecastab AO-70, Adecastab AO-80 and Adecastab AO-330i (the above are manufactured by Asahi Denka Co., Ltd.). The hindered amine antioxidants include Sanol LS2626, Sanol LS765, Sanol LS770, Sanol LS744, Tinuvin 144, Tinuvin 622LD, Mark LA57, Mark LA67, Mark LA62, Mark LA68, Mark LA63 and Sumilizer TPS, and the phosphite antioxidants include Mark 2112, Mark PEP-8, Mark PEP-24G, Mark PEP-36, Mark 329K and Mark HP-10. Of these, the hindered phenol and hindered amine antioxidants are particularly suitable, in embodiments.  
      There is no particular limitation on the thickness of the silicon-containing layer, however, in embodiments, the silicon-containing layer may be in the range from about 2 to about 5 μm in thickness, such as from about 2.7 to about 3.2 μm in thickness.  
      The electrophotographic photoreceptor of embodiments may be either a function-separation-type photoreceptor, in which a layer containing a charge generation substance (charge generation layer) and a layer containing a charge transport substance (charge transport layer) are separately provided, or a monolayer-type photoreceptor, in which both the charge generation layer and the charge transport layer are contained in the same layer, as long as the electrophotographic photoreceptor of the particular embodiment has the photosensitive layer provided with the above-mentioned silicon compound-containing layer. The electrophotographic photoreceptor will be described in greater detail below, taking the function-separation-type photoreceptor as an example.  
       FIG. 1  is a cross-sectional view schematically showing an embodiment of the electrophotographic photoreceptor of the disclosure. The electrophotographic photoreceptor  1  shown in  FIG. 1  is a function-separation-type photoreceptor in which a charge generation layer  13  and a charge transport layer  14  are separately provided. That is, an underlayer  12 , the charge generation layer  13 , the charge transport layer  14  and a protective layer  15  are laminated onto a conductive support  11  to form a photosensitive layer  16 . The protective layer  15  contains a resin soluble in the liquid component contained in the coating solution used for formation of this layer and the silicon compound. The various layers of the photoreceptor shown in  FIG. 1  are generally known, and are described in detail in the above-mentioned commonly owned and copending applications, the entire disclosures of which are incorporated herein by reference.  
      The electrophotographic photoreceptor of embodiments should not be construed as being limited to the above-mentioned constitution. For example, the electrophotographic photoreceptor shown in  FIG. 1  is provided with the protective layer  15 . However, when the charge transport layer  14  contains the resin soluble in the liquid component in the coating solution used for formation of this layer and the silicon compound, the charge transport layer  14  may be used as a top surface layer (a layer on the side farthest apart from the support  11 ) without using the protective layer  15 . In this case, the charge transport substance contained in the charge transport layer  14  is desirably soluble in the liquid component in the coating solution used for formation of the charge transport layer  14 . For example, when the coating solution used for formation of the charge transport layer  14  contains an alcohol solvent, the silicon compounds described above, such as compounds represented by the following formulas, can be used as the charge transport substances.  
                 
                 
                 
                 
 
      In embodiments, a particularly suitable charge transport molecule is the following arylamine (Compound C- FIG. 5 ):  
                 
 
       FIG. 3  is a cross-sectional view showing another exemplary embodiment of an image forming apparatus. The image forming apparatus  220  shown in  FIG. 3  is an image forming apparatus of an intermediate transfer system, and four electrophotographic photoreceptors  401   a  to  401   d  are arranged in parallel with each other along an intermediate transfer belt  409  in a housing  400 .  
      Here, the electrophotographic photoreceptors  401   a  to  401   d  carried by the image forming apparatus  220  are each the electrophotographic photoreceptors. Each of the electrophotographic photoreceptors  401   a  to  401   d  may rotate in a predetermined direction (counterclockwise on the sheet of  FIG. 3 ), and charging rolls  402   a  to  402   d , developing device  404   a  to  404   d , primary transfer rolls  410   a  to  410   d  and cleaning blades  415   a  to  415   d  are each arranged along the rotational direction thereof. In each of the developing device  404   a  to  404   d , four-color toners of yellow (Y), magenta (M), cyan (C) and black (B) contained in toner cartridges  405   a  to  405   d  can be supplied, and the primary transfer rolls  410   a  to  410   d  are each brought into abutting contact with the electrophotographic photoreceptors  401   a  to  401   d  through an intermediate transfer belt  409 .  
      Further, a laser light source (exposure unit)  403  is arranged at a specified position in the housing  400 , and it is possible to irradiate surfaces of the electrophotographic photoreceptors  401   a  to  401   d  after charging with laser light emitted from the laser light source  403 . This performs the respective steps of charging, exposure, development, primary transfer and cleaning in turn in the rotation step of the electrophotographic photoreceptors  401   a  to  401   d , and toner images of the respective colors are transferred onto the intermediate transfer belt  409 , one over the other.  
      The intermediate transfer belt  409  is supported with a driving roll  406 , a backup roll  408  and a tension roll  407  at a specified tension, and rotatable by the rotation of these rolls without the occurrence of deflection. Further, a secondary transfer roll  413  is arranged so that it is brought into abutting contact with the backup roll  408  through the intermediate transfer belt  409 . The intermediate transfer belt  409  which has passed between the backup roll  408  and the secondary transfer roll  413  is cleaned up by a cleaning blade  416 , and then repeatedly subjected to the subsequent image formation process.  
      Further, a tray (tray for a medium to which a toner image is to be transferred)  411  is provided at a specified position in the housing  400 . The medium to which the toner image is to be transferred (such as paper) in the tray  411  is conveyed in turn between the intermediate transfer belt  409  and the secondary transfer roll  413 , and further between two fixing rolls  414  brought into abutting contact with each other, with a conveying roll  412 , and then delivered out of the housing  400 .  
      According to the exemplary image forming apparatus  220  shown in  FIG. 3 , the use of electrophotographic photoreceptors of embodiments as electrophotographic photoreceptors  401   a  to  401   d  may achieve discharge gas resistance, mechanical strength, scratch resistance, etc. on a sufficiently high level in the image formation process of each of the electrophotographic photoreceptors  401   a  to  401   d . Accordingly, even when the photoreceptors are used together with the contact charging devices or the cleaning blades, or further with the spherical toner obtained by chemical polymerization, good image quality can be obtained without the occurrence of image defects such as fogging. Therefore, also according to the image forming apparatus for color image formation using the intermediate transfer body, such as this embodiment, the image forming apparatus which can stably provide good image quality for a long period of time is realized.  
      The disclosure should not be construed as being limited to the above-mentioned embodiments. For example, each apparatus shown in  FIG. 2  or  3  may be equipped with a process cartridge comprising the electrophotographic photoreceptor  1  (or the electrophotographic photoreceptors  401   a  to  401   d ) and charging device  2  (or the charging devices  402   a  to  402   d ). The use of such a process cartridge allows maintenance to be performed more simply and easily.  
      Further, in embodiments, when a charging device of the non-contact charging system such as a corotron charger is used in place of the contact charging device  2  (or the contact charging devices  402   a  to  402   d ), sufficiently good image quality can be obtained.  
      An example is set forth hereinbelow and is illustrative of different compositions and conditions that can be utilized in practicing the disclosure. All proportions are by weight unless otherwise indicated. It will be apparent, however, that the disclosure can be practiced with many types of compositions and can have many different uses in accordance with the disclosure above and as pointed out hereinafter.  
     EXAMPLES  
     Example 1  
     Preparation of Arylamine Intermediate in an Ionic Liquid  
      To a 500 mL flask fitted with mechanical stirrer, argon inlet and reflux condenser is charged palladium(II)acetate (0.47 g, 0.01 mol %) and tri-t-butylphosphine stock solution (0.46 mL 2.7 mmol) and dissolved in 75 mL toluene. The solution is stirred for 1 hour to allow for dissolution of palladium acetate. Then sequentially, 75 mL of (tetradecyl)trihexyl phosphonium chloride, 4-bromobiphenyl (50 g, 224 mmol), diphenylamine (39.7 g, 235 mmol), and sodium t-butoxide (38.7 g, 403 mmol) are added with stirring. The reaction is heated to 90° C. over a 30 min period. A large exotherm is observed and the heating is shut off. After 1 hr 15 min the exotherm subsides and HPLC analysis confirms complete conversion of diphenylamine to N-biphenyl-diphenylamine.  
      Following completion of the reaction, the reaction mixture is cooled to room temperature (about 20° C. to about 25° C.), and hexane and water are added to produce a triphasic medium. The top organic layer is removed, and is treated with Filtrol-24 and Al 2 O 3  at 90° C. for 2 hours. The absorbents are filtered while the solution is hot. The hexane solution is concentrated and isopropanol is added followed by methanol to complete precipitation of N-biphenyl-diphenylamine. The solid N-biphenyl-diphenylamine is filtered and washed with methanol, air dried then finally vacuum dried (60° C./5 mmHg) overnight. Ashing followed by ICP analysis does not detect any residual palladium present.  
      The middle ionic liquid phase is collected and dried. The reaction is repeated again with re-charging of the reactants, as described above. The process proceeds in the same manner, with the same results, indicating that the palladium catalyst is recycled.  
     Comparative Example 1  
     Preparation of Arylamine Intermediate in an Organic Solvent  
      To a 2 L flask fitted with mechanical stirrer, argon inlet and reflux condenser is charged palladium(11)acetate (1.57 g, 5 mol %) and 226 mL of tri-t-butylphosphine stock solution (5 g tri-t-butylphosphine in 1 L toluene). The solution is stirred for 1 hour to allow for dissolution of palladium acetate. Then sequentially, 4-bromobiphenyl (164 g, 1.0 equiv), diphenylamine (130 g, 1.05 equiv), toluene (410 mL) and sodium t-butoxide (127 g) are added with stirring. The reaction is heated to 70° C. over a 30 min period. A large exotherm is observed and the heating is shut off. After 1 hr 15 min the exotherm subsides and HPLC analysis confirms complete conversion of diphenylamine to N-biphenyl-diphenylamine.  
      Following completion of the reaction, toluene (200 mL) is added and the solution is filtered to remove insoluble materials. The solids are washed with toluene so as to have a final liqueur with a volume of 2 L. This solution is treated with Filtrol-24 (40 g) and Al 2 O 3  (40 g) at 90° C. for 2 hours. The absorbents are filtered while the solution is hot. A second treatment with Al 2 O 3  (8 g) at 90° C. is necessary to completely remove color (most likely residual palladium catalyst). The toluene solution is concentrated to 400 mL and isopropanol (500 mL) is added followed by methanol (750 mL) to complete precipitation of N-biphenyl-diphenylamine. The solid N-biphenyl-diphenylamine is filtered and washed with methanol (250 mL), air dried then finally vacuum dried (60° C./5 mmHg) overnight. The final yield of N-biphenyl-diphenylamine is 214.85 g (95.1%). HPLC, 1H NMR and elemental analysis confirm purity of N-biphenyl-diphenylamine at &gt;99.5%. Ashing followed by ICP analysis does not detect any residual palladium present and is presumed by absorption to either the Al 2 O 3  or the Filtrol-24 or both.  
      It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticiapted alternatives, modifications, vibrations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.