p , ‘ 2,924,620 United Sttes atent 0 ICC Patented Feb. 9, 1960

1 2 gish or fails entirely. It is highly desirable that the acti 2,924,620 vating group be easily and economically removed after it has served its purpose. Even with the activating PROCESS FOR THE PREPARATION OF N-acetyl group, the reaction is rather slow, about 20 to DIPHENYLAMINES 24 hours at elevated temperatures being required to Robert K. Miller, New Castle, Del., assignor to E. I. du achieve practical yields of the product of the condensation. Pont de Nemonrs and Company, Wilmington, Del., a It is an object of the present invention to utilize corporation of Delaware formanilides in the Ullmann condensation with aryl halides wherein the diarylamine is directly recoverable N0 Drawing. Application March 30, 1959 10 from the reaction mass. Serial No. 802,664 it is a further object of this invention to eliminate the 5 Claims. (Cl. 260-576) need for prolonged hydrolysis of the reaction product obtained from N-acetyl primary aromatic amine and aryl The present invention is directed to a novel method halide. ' for producing diphenylamines; this invention is particu 15 It is a further object of this invention to produce un larly useful in the preparation of unsymmetrical diphenyl expectedly high yields of diarylamine. amines. It is a speci?c object of the present invention to pro This application is a continuation-in-part of copending vide a simpli?ed and economically practical Ullmann applications Serial No. 592,732, ?led June 21, 1956 and condensation method for preparing 3-chlorodiphenyl application Serial No. 598,736, ?led July 19, 1956, both amine. applications now abandoned. It is a speci?c object of the present invention to pro Diarylamines have long been important intermediates vide a simpli?ed and economically practical Ullmann in the chemical industry. Recently they have been em condensation method for preparing both symmetrical and ployed in the preparation of phenothiazines, particularly unsymmetrical diphenylamines. ring-substituted phenothiazines which are further con 25 The present ‘invention is based on the use of form verted into such -N-substituted phenothiazines as 10-(3— anilides in lieu of the prior art acetanilides in the produc dimethylaminopropyl)-2—chlorophenothiazine, a tranquil tion of diphenylamines on condensation with aryl halides izing agent in medicinal use known as chloropromazine in the presence of a copper Ullmann condensation cata (see US. Patent 2,645,640 and British Patent 716,205). lyst and potassium or sodium carbonate as acid acceptors. Several general routes to diarylamines are known. One 30 It has been discovered that, when formanilides rather typical method, suitable for the preparation of symmetri~ than the acetanilides suggested in the prior art are em cal diphenylamines, consists of heating the primary aro~ ployed in the Ullmann condensation, the reaction time matic amine with its corresponding hydrochloride, e.g., is signi?cantly shortened and the product of the con aniline and aniline hydrochloride yield ammonium chlo densation obtained in higher yield. ride and diphenylamine; it is impractical for preparing In one embodiment of the present invention sym unsymmetrical diphenylamines; e.g., heating aniline hy metrical and unsymmetrical diphenylamines are obtained drochloride with toluidine gives a di?icultly separable mix by reacting (A) a compound taken from the group con ture of diphenylamine, methyldiphenylamine and dimeth sisting of formanilide and the alkyl, alkoxyl, ?uoro and yldiphenylamine. More practical for the preparation of chloro substituted formanilides with (B) a compound unsymmetrical diphenylamines is the Ulhnann conden 40 taken from the group consisting of bromobenzene, iodo sation which may be used in several modi?cations, all benzene and alkyl, alkoxyl, ?uoro and chloro substituted involving reaction of an aryl halide with an aryl amine bromo and iodobenzenes in the presence of a copper in the presence of an activating substituent and a copper Ullmann condensation catalyst and potassium carbonate catalyst. ‘In one modi?cation, an ortho-haloaromatic at a temperature within the range of 170-240° C. and carboxylic acid is condensed with an aromatic primary recovering the diphenylamine from the reaction mass. amine and the resulting orthocarboxy diarylamine is then 45 It has also been discovered that when potassium car thermally decarboxylated, e.g., 3-chlorodiphenylamine is bonate is employed as the acid-acceptor in this condensa obtained from either (a) 2,4-dichlorobenzoic acid and tion the diphenylamines rather than the expected N-acyl aniline or (b) 2-chlorobenzoic acid and 3-chloroaniline. diphenylamines are obtained directly from the reaction A variation on the above method involves reacting an mass as the major product. Thus the hydrolytic step of thranilic acid with bromobenzene to obtain the intermedi 50 the prior art is no longer necessary and the process is ate N-phenyl-anthranilic acid. unexpectedly simpli?ed. Furthermore, use of a form These processes su?er a major disadvantage in that anilide materially shortens the required time and the introducing the activating carboxyl group into the re overall yield of the diphenylamine is substantially as actant is costly and the diarylamine is obtained at the good as or better than that obtained following the old expense of the carboxyl group which is lost as CO2 in 55 practice. ' an additional unit operation. Another embodiment of the present invention com Another known routine to the preparation of diaryl prises reacting (A) a formanilide with (B) bromoben amines employs an aryl amine which is activated by a zene in the presence of a copper Ullmann condensation nitro group, such as o-nitroaniline or by an N-acetyl catalyst and sodium carbonate at a temperature within group. It is known that acetanilide and bromobenzene 60 the range of 170\-240° C. and recovering the diphenyl yield N-acetyl-diphenylamine, hydrolyzable to diphenyl amine from the reaction mass after hydrolyzing the reac amine on heating in alcoholic hydrochloric acid for 3 tion product. hours (Goldberg, Berichte 40, 4541 (1907)); that N The prior art describes the use of a wide variety of acetyl 0- (or p~) toluidine yields N-acetyl methyldi acetanilides and phenyl bromides (and iodides) in the phenylamine, saponi?able in hot alcoholic alkali to the 65 Ulhnann condensation reaction; that is, these reactants 0- (or p-) methyldiphenylamine. (Weston and Adkins, may contain alkyl, alkoxyl, chloro and ?uoro groups, all Journ. Am. Chem. Soc. 50, 859 (1928).) One disadvantage of this known method utilizing an of which are inert under the conditions of the condensa 'N-acetyl group is that a time consuming costly hydroyltic tion reaction as more fully described below. Thus, proper selection of the organic reactants a?ords N-acety‘ldi step is required to remove the activating group. In the 70 absence of the activating nuclear carboxyl group or the phenylamines which are substituted in one phenyl ring by N-acetyl group, the reaction is either impractically slug one or more substituents and are unsubstituted in the 2,924,620

3 ~ ~ " other phenyl ring’, or which are substituted in both phenyl not more than 50 mol percent excess and for reasons of rings by the same or different groups which may occupy economy not more than 5 mol percent excess. When the same or diiferent positions on the two phenyl rings. relatively large excesses of bromobenzene are present, >The point of the invention resides in the presence of the re?uxing excess tends to maintain the reaction mass the N-forniyl group and ‘is independent of the presence of at the lower temperaturelimit, and, unless superatmos other siib'stituents on the phenyl rings in the organic pheric' pressures are employed’ to raise the boiling reactants so long as these other substituents are inert point of the mixture, the time required to complete the (i.e., unaltered) under the conditions of the Ullmann condensation is materially lengthened. An excess of N condensation. Alkyl, alkoxyl and halo groups ‘other formyl-m-chloroaniline of up to about 20 mol percent than bromo and iodo are inert substituents in this reac 10 is practical; however, as stated above, for best results tion and may be present in either of the organic re and for reasons of economy, approximately stoichiometric actants. _ p quantities of organic reactants are employed. The alkyl substituents are preferably lower-alkyl groups The rate of condensation becomes practical at temper of from 1 to 4 carbon atoms, particularly methyl and atures of approximately 170:5” C. and above. With ethyl, for reasons of economy and availability of the sub bromobenzene as the aryihalide, this initial lower tem ject intermediates. Likewise the preferred alkoxyl groups perature corresponds to the reflux temperature of the mix are methoxyl, ethoxyl, propoxyl, and butoxyl, particular ture. ‘While external heat’ is being applied, the re?ux l_y methoxyl. A ?uoro or chloro group, incontr'ast to temperature of the mass rises as bromobenzene is con bromo- or iodo-, is relatively inert under conditions of sumed. Although the reaction proceeds at the lower end the reaction, and, as indicated above, may be present in 20 of the stated temperature range it is preferred to allow either of the reactants; . . . . the temperature of the reaction mass to rise to ZOO-220° Representative formanilides which may be employed C. Loss of the formyl' group (when potassium carbonate according to ‘the method of this invention are: form is the acid-acceptor) takes place more rapidly at the anilide, m-?uoroformanilide, m-chloroformanilide, N higher than at the lower temperatures. Temperatures of formyl-o- (or p-) toluidine, N-formyl-m-ethylaniline, m 25 up to about 240° C. may be employed. In general no methoxyformanilide, 2,4-dimethylformanilide, and the further advantages are gained on exceeding 240° C., and like as de?ned. it is seldom necessary to exceed 220° C. to achieve an Representative phenylhalides are: bromobenzene, iodo economically practical rate of reaction. The heat input benzene, p-bromotoluene, m-?uoro-bromobenzene, p-iodo is then regulated to maintain the mass at these temper~ chlorobenzene, m-methoxybromobenzene, p - methoxy atures, preferably at about 210° C. In the condensation bromobenzene, 2,4-dimethylbromobenzene, and the like. step, the formyl derivatives are remarkably more reactive In general, any of the formanilides may be employed than the corresponding acetyl derivatives. For example, with any of the phenyl bromides or iodides for the prep the time required to reach the maximum preferred temper aration of symmetrical or unsymmetrical diphenylamines. ature is cut by a factor of about 4 when m-chloroacet The method of this invention is particularly useful for 35 anilide is replaced by m-chloroformanilide under com preparing unsymmetrical diphenylamines, since such parable. conditions; the holding time at the higher tem amines are di?icultly or not at all obtainable free of perature to complete the condensation is also shortened isomers by the more. conventional methods. Thus by with the result that the overall reaction time is cut in proper selection of the organic reactants, diphenylamines half. The actual times required depend upon such factors may be obtained which are substituted in one phenyl ring 40 as the particular organic‘reactants and their mol ratios, by one or more substituents and unsubstituted in the other; and on the nature of and quantities of the copper catalyst (4 or which are substituted in both phenyl rings by the same and acid-acceptor. ' . or diiferent groups which may occupy the same relative A variety of Ullmann condensation catalysts may be positions or different positions on the two phenyl rings. employed. By Ullmann condensation catalyst is meant Representative diphenylamines which may be prepared metallic copper in suitable form and compounds of copper according to the present invention are diphenylamine, 2 which are normally engaged in the art to elfect condensa and 4-methyldiphenylamine, 2,4'-dimethyldiphenylamine tions of this type. Representative and suitable catalysts (ditolylamine), 3,4,3’,4' - tetramethyldiphenylamine, 3 are copper powder, copper-bronze powder, copper and ?uorodiphenylamine, 3 - chlorodiphenylamine, 3,3’ -di iodine mixture, copper halides such as cuprous iodide, chlorodiphenylamine, 3 -methoxydipheny1amine, 4 ~meth- . cuprous bromide and cuprous chloride, cupric carbonate, oxydiphenylar'nine, 3 - methoxy - 3' - methyldiphenyl cupric acetate and the ‘like described in the art, prefer amine, and the like as de?ned above. In the preferred ably cupric ‘carbonate. Only relatively small quantities embodiment of the invention, 3-chlorodiphenylamine is of catalyst are required; practical quantities are from prepared by reacting m-chloroformanilide (N-formyl-n1~ about 1 to 10% by weight of the formanilide. Lesser chloroaniline) with bromobenzene. ' 55 quantities do not always provide for consistently practical Except for the use of a formanilide rather than an rates of condensation, while larger ' quantities, though acetanilide, the present process follows the practice of operable, do not always‘ provide additional advantages the art with regard to the general reaction conditions. commensurate with increased cost. About 3% by weight Best results are generally obtained in the absence of of cupric carbonate is preferred. solvent or diluent, while employing substantially an hydrous materials under anhydrous conditions. In the 60 The acid-acceptor, potassium or sodium carbonate, will preferred general method, a mixture consisting of a form~ be employed in quantities providing from one to three anilide, such as N-forrnyl-m-chloroaniline, an aryl equivalents, preferably at least two equivalents (one halide such as bromobenzene, and potassium ‘carbonate molar equivalent), based on the theoretical quantity of acid-acceptor and an Ullmann condensation catalyst such halide to be produced in the metathetical reaction be as copper or a compound of copper is heated to and held 65 tween the formanilide and the aryl halide reactants. at temperatures ranging from about 170 to 220° C. at The detailed mechanism of the present invention where normal pressures, until stoichiometric equivalents of the in potassium carbonate is the acid-acceptor and wherein ‘organic reactantsare substantially consumed. the formyl group is removed is not known with cer a It is preferred to employ approximately stoichiometric ’ tainty; it appears that this unexpected result is intimately 70 associated with potassium bicarbonate which is produced ‘quantities of the organic reactants in the absence of, addi in situ in the reaction mass. A possible explanation is 'tional solvent or diluent. If, desired, however, either of that the potassium bicarbonate decomposes, in the tem the organic reactants may be in excess. In the preparation perature range employed, into potassium carbonate, CO2 “of .Vth'e preferred S-chlor'odiphenyIamine, for example, and H20; said water produced in situ removes the forrnyl best results are obtained if bromobenzene is employed in group from the N-forinyldiphenylamine. - 2,924,620 6 As‘ stated earlier, Ullmann condensations of the present Example 2 type proceed best using anhydrous substances under an hydrous conditions. However, in the present invention it A mixture consisting of 155.6 parts (1.0 mol) m—chlo~ is not critical to prepare and maintain completely an roformanilide, 157 parts (1.0 mol) bromobenzene, 172.6 hydrous reactants and reagents. To do so is inconven parts (1.25 mol) potassium carbonate, and 10 parts ient, time-consuming and costly. Instead, we employ (0.081 mol) cupric carbonate was heated to re?ux (166° materials which are normally considered by those skilled C.) rwhile being stirred. Any two-phase distillate that in the art to be anhydrous, i.e., not obviously grossly appeared during this period was condensed and separated contaminated. In practice small quantities of water in in an azeotropic distillation head, the water being dis variably begin to appear in the re?uxing vapor in the carded and the bromobenzene returned to the reaction initial stages of the reaction. At the reaction temper vessel. As bromobenzene was consumed the tempera atures employed the water is readily removed from the ture rose, in 55 minutes, to 207° C. The reaction mass reaction zone as the azeotrope with the aryl halide, e.gl, was held at 205:5". C. for v10 hours, cooled, and ex bromobenzene. - tracted with 800 parts carbontetrachloride. The extract after being ?ltered through Celite (a ?lter aid) was con The diphenylamine produced according to the method 15 of this invention, with potassium carbonate as acid centrated in vacuo and then distilled to give: acceptor, is readily isolated from the crude reaction mass in high yield under non-hydrolytic conditions. The re Fraction IB.P., Press. Wt., an?" ° 0. mm. Hg Parts action mass may be extracted with an organic solvent 20 such as benzene, chlorobenzene, o-dichlorobenzene and 128-141 0. 5-0. 1 141. 1 1. 6483 the like to separate the organic from inorganic com 141-153 0. 6 9. 7 1. 6432 ponents, and the extract evaporated to recover the crude product, which, if desired, may be distilled, or crystallized Fractions A and B combined represent a yield of ap from conventional solvents. Alternately, the reaction proximately 74% of 3-chlorodiphenylamine containing mass may be drowned in water, the organic layer sep roughly 10% of the N~formyl derivative as determined arated and either distilled or crystallized in the usual way. by analysis of the infrared spectrum. Steam-volatile products such as diphenylamine may be Fraction A was redistilled to yield as a main cut, steam distilled directly from the reaction mass. Occa 95.0 parts (46.6% yield) of substantially pure m-chloro sionally it is found that the crude products contain up diphenylamine, identical to an authentic sample in boil to 10% of carbonyl compounds, calculated as ‘the N ing range (117-120° C. at 0.2 mm. Hg), refractive index formyldiphenylamine. These may be removed by frac (111320 1.6503), quantitative elemental analysis (‘for C, tionally distilling the organic product, or where the di H, N, Cl) and infrared spectrum. This sample, now phenylamine is a solid, by crystallization from solvents. containing" less than 5% of carbonyl compound, is suit m-Chloro-diphenylamine prepared according to the able for conversion'into 2-chlorophenothiazine (approxi method of this invention is suitable for the preparation mately 60% yield, M.P. l98—200° C.) by {using with sul of 2-chloro-phenothiazine following the procedures de fur in presence of iodine, following the method described scribed in the art. in British Patent 716,205. Example 1 In the above example simple distillation technics were employed in isolating the product. If pure 3-chloro A mixture consisting of 226.4 parts (1.87 mols) form diphenylamine is required, i.e., essentially free of car anilide, 294 parts ( 1.87 mols) bromobenzene, 345.2 parts bonyl-containing impurity, the crude reaction product is (2.5 mols) potassium carbonate, and 5 parts (0.04 mol) fractionated through a packed multi-plate distillation cupric carbonate was heated to re?ux (168° C.) while column, overall yields of at least 60% of recti?ed prod being stirred. During this time, any two-phase conden uct being obtained. sate which appeared was separated in an azeotropic dis 45 Example 3 tillation head, the water being discarded and the bromo benzene returned to the reaction vessel. The temper The procedure of Example 2 was repeated using 311.2 ature of the mass rose from 168° C. to 205° C. in 2.5 parts m-chloroformanilide, 350 parts bromobenzene, 345 hours. The external source of heat was then regulated parts potassium carbonate and 25 parts copper carbonate. . The total reaction time was 11.5 hours. The reaction to maintain the contents of the reaction vessel at 210i5° 50 C. for 10 hours. The charge was cooled to about 100°’ mass was cooled to about 100—110° C. and ?ltered. The C., thoroughly extracted with chlorobenzene (600 parts) inorganic ?lter cake was thoroughly washed with ap and ?ltered. The ?ltrate was stripped of chlorobenzene proximately 600 parts chlorobenzene, and the combined under reduced pressure and distilled at 10 to 15 mm. ?ltrate and washings were stripped in vacuo of the sol vent. The residue 'was distilled at 0.2 to 0.5mm. of Hg pressure: 261.2 parts (82.6% yield) of diphenylamine 55 were collected, boiling in the range 155 to 175° C. and Hg to give 1.2 parts boiling at 30-105° C. and 316.8 melting in the range 36 to 48° C. Analysis of the parts of crude 3-chlorodiphenylamine, B.P. 117-160“ C., infrared spectrum showed less than 5% of carbonyl 11132" 1.6458. - containing substance, calculated as N-formyldiphenyl 291.2 parts of the crude 3-chlorodiphenylamine wa amine. Recrystallized from a 1:2 mixture of benzene recti?ed at 10 mm. Hg pressure through a 24-inch col 60 umn (rated at about 20 theoretical plates) and at a re?ux and petroleum ether this product melted at 49.5-51.5 ° ratio of 10/ 1. C. (no depression on admixture with authentic diphenyl amine, M.P. 53° C.), and had no carbonyl band in its infrared spectrum which was identical to that of authentic Weight, Percent Fraction Parts Car diphenylamine. 65 bonyl 1 Equally good or somewhat better yields are obtained on working up the reaction mass by alternate methods: big For example, (a) the benzene extract of the reaction mass, 3 . 0 instead of being distilled is concentrated to small volume, 1. 6512 1 diluted with petroleum ether and chilled to obtain pure 1. 6501 6 OrPlOOD' high crystalline diphenylamine; (b) the reaction mass is high drowned in water, the organic components removed and 99999039050 osbsoooworrow distilled to obtain pure product boiling at 160-165" C. llnt‘rared analysis: The impurity in fraction 1 is m-chloroformanilide; and 5 mm. Hg pressure; (c) the reaction mass is drowned fractions 6 and 7 show high content of N-formyl 3~chlorodiphenylamine. in water and steam distilled to recover the diphenylamine. ’ Fractions 2, 3, 4 and 5 represent a 67.9% yield of 3-chlorodiphenylamine. 2,924,620 8 Example 4 reaction mass to reach 208° C. is 8 hours. Holding the reaction mass at ZOO-210° C. for 16 hours more and then A mixture consisting of 155.6 parts (1 mol) rn-chloro hydrolyzing and working up as described above gives formanilide, 157 parts (1 mol)\bromobenzene, 207 parts pure 3-chlorodiphenylamine in yields of 60 to 70%. (1.5 mols) potassium carbonate, and 10 parts (0.081 Since in general it is found that increasing the reac mol) cupric carbonatewas treated as described in Ex tion time-at 210° C. results in- somewhat better yields, ample 2. The temperature rose from the initial re?ux the above example shows that rn-cbloroformanilide is temperature of 167° C. to>208° C. in 1.5 hours. After much more reactive than m-chloroacetanilide under com being held at about 210° C. for 10 hours, the reaction parable conditions and alfords higher yields of 3-chloro mass was cooled to 100° C. and stirred into 1000. parts diphenylamine. water. The water-immiscible organic layer was removed In the above examples powdered metallic copper or and distilled: copper bronze or copper salts, e.g., cuprous iodide or chloride, may replace cupric carbonate with similar Fraction B.P., Press, Wt., m.” results being obtained. ° C. mm. Hg Parts 15 In the examples given, the reactors were heated by electrical means; however, for commercial use, especial 143. 3 l. 0501 4. 9 1.. 6477 ly on a large scale, it is preferred to circulatehot vapor, 7. 3 1. 6445 such as superheated steam or a hot liquid, such as Dow therm through a jacketed vessel to maintain the reaction Fraction A corresponds to a 70% yield of m-chloro mass at the desired temperature within the range of diphenylarnine containing less than 5% of carbonyl com 170-240° C. This latter method of heating avoids local pound. B and C arelesspure in that they contain larger overheating and charring of the charge resulting in im quantities of carbonyl compound as shown by their in proved overall yields of the desired end product. frared absorption spectra. Pure 3-chlorodiphenylamine Substantially identical results are achieved in Examples (13.1’. 120:5“ C. at 0.1 to 0.3 mm. Hg, 11;?" 1.6503) 1 to 5 by replacing formanilide and m-chloroformanilide may be obtained free of carbonyl impurity by recti?ca by other substituted formanilides such as Z-methylforrn tion through a multi-plate distillation column. anilide, 4-methylformanilide, 3-ethylformanilide, 3,4 dimethylformanilide, and 3-methoxyformanilide to yield Example 5 directly the corresponding unsymmetrical diphenyl 121.1 parts (1.00 mol) of formanilide, 200 parts (1.07 30 Likewise, instead of bromobenzene and 4 mol) of p-bromoanisole, 172.6 parts (1.25 mol) of po~ methoxybromobenzene in the above examples, analogs tassiurn carbonate, and 2.5 parts of cupric carbonate were and homologs such as 3-bromoethylbenzene, 4-iodotolu stirred and heated together at 210:5° C. for 15 hours. ene, S-methoxybromobenzene, 4-ethoxyiodobenzene and During this time about 10 parts of-water was collected 3-chloroiodobenzene may be employed with any of the as distillate. The reaction mass was cooled, extracted ‘ formanilides listed above to produce directly the sym with 550 parts of chlorobeuzene and ?ltered, the ?lter metrically- and unsymmetrically-substituted diphenyla cake was washed with 250 parts chlorobenzene and the mines described earlier in the speci?cation. Thus, con combined ?ltrate and washings were evaporated under densation of m-chloroformanilide with 3-chloroiodoben reduced pressure at a pot temperature of up to 110° C. zene yields 3,3’-dichlorodiphenylamine; condensation of The oily crystalline residue was recrystallized from 220 ,_ 3-methoxyformanilide with 3-methoxyiodobenzene yields parts of methanol to yield 119.3 parts of 4-methoxy 3,3'-dimethoxydiphenylamine; condensation of N-formyl diphenylamine, M.P. 101—103° C. in 59.9% yield. Fur p-toluidine with 4-ethoxyiodobenzene yields 4-methyl-4’ ther recrystallization ‘from methanol or benzene raises ethoxydiphenylamine. the melting point to a maximum of 105—106° C. 4 If the corresponding N-acetylanilines are employed in methoxydiphenylami-ne, prepared from p-acetoanisidine the above Examples 1 to 5 the products are the N-acetyl and bromobenzene, is reported to melt at 105° C. diphenylamines. In a control experiment using m-chlo land and Wecker, Ber. 43, 708). roacetanilide it is found that the time required for the temperature of the reaction mass to rise to the preferred Example 6 maximum temperature of about 210° C. is about 4 times A mixture consisting of m-chloroformanilide, 155.6 , and the overall reaction time about 2 times that for the parts; bromobenzene, 157 parts; sodium carbonate, 159 m-chloroformanilide. To convert the resulting reaction parts; copper carbonate, 3.5 parts was heated to re?ux mass to 3-chlorodiphenylamine it has to be heated for while being stirred; the temperature of the stirred ‘reac 3 to 4 hours in alcoholic hydrochloric acid or in alcoholic tion mass rose to 208° C. in 2 hours. The reaction mass caustic to split 01f the acetyl group. Best yields obtain was then held at 200—210° C. for 10 hours. During able under these conditions are 60-65%. On the other this time, any two-phase condensate which appeared was hand, if the reaction mass obtained in controlled experi separated in an azeotropic distillation head, the water ments using m-chloroformanilide is also subjected to the being discarded and the bromobenzene returned to the same hydrolytic conditions the yield of 3-chlorodiphenyl reaction vessel. The mixture was cooled somewhat and amine by this longer process is of the order of 70—79%. 165 parts methanol was added slowly (any methanol The process of the present invention offers unexpected vaporized by the'hot mixture was condensed and returned and bene?cial results. The formanilides are more easily to the reaction- vessel), followed by 118 parts concen and more economically prepared, requiring only' aqueous trated (36% by wt.) hydrochloric acid. The mixture formic acid for formylation whereas acetylation is best was heated under re?ux for 4 hours and then drowned accomplished by means of the anhydride. Furthermore, in 850 parts water. The oil layer was separated and the formanilides are much faster reacting in the Ullmann distilled at reduced pressure to give 149 parts (73% condensation, in general about half the time being re yield) of pure 3-chlorodiphenylamine. quired to obtain yields of diphenylamine which are on In general when this experiment is repeated using this: average higher than those obtainable with the acetani sodium carbonate and the crude N-fonnyl-3-chlorodi 1 es. phenylamine is hydrolyzed in hot alcoholic mineral acid 70 As many apparently widely different embodimentsof or in hot alcoholic alkali, the yields of pure 3'-chlorodi this invention may be made without departing from the phenylamine range from .70 to.80%. spirit and scope thereof, it is to be understood that the If m-chloroacetanilide (169.7 parts) is employed in invention is not limited to the speci?c embodiments stead of m-chloroformanilide (155.6 parts) in the above thereof except as de?ned inthe appended claims. example, the time required for the temperature of the The embodiments of the invention in which. an exclu 2,924,620 10 sive property or privilege is claimed are de?ned as fol a temperature within the range of 170 to 220° C. and lows: recovering the 3-ch1orodiphenylamine from the reaction 1. The process of preparing symmetrical and unsym mass. metrical diphenylamines which process comprises react 4. The process for the preparation of 3-chlorodiphen ing (A) a compound taken from the group consisting 5 ylamine which comprises reacting m-chloroformanilide of formanilide, alkyl-substituted formanilides, alkoxyl with bromobenzene in the presence of a copper Ullmann substituted formanilides, ?uoro-substituted formanilides, condensation catalyst and sodium carbonate as acid and chloro-substituted formanilides with (B) a com acceptor at a temperature within the range of 170-220° pound taken from the group consisting of bromobenzene, (3., followed by hydrolysis of the resulting N-formyl iodobenzene, alkyl-substituted bromobenzene, alkoxyl 10 diphenylamine and recovering 3-chlorodiphenylamine substituted bromobenzene, ?uoro-substituted bromoben from the reaction mass. zene, chloro-substituted 'bromobenzene, alkyl-substituted 5. The process of claim 4 wherein the copper Ullmann iodobenzene, alkoxyl-substituted iodobenzene, ?uoro condensation catalyst is taken from the group consisting substituted iodobenzene, and chloro-substituted iodoben ' of copper powder, copper bronze, cuprous bromide, zene in the presence of a copper Ullmann condensation 15 cupric carbonate, cuprous iodide and cuprous chloride. catalyst and potassium carbonate at a temperature within the range of 170 to 240° C. and recovering the corre References Cited in the ?le of this patent sponding diarylamine directly from the reaction mass. 2. The process of claim 1 wherein the Ullmann con UNITED STATES PATENTS densation catalyst is taken from the group consisting 20 2,572,067 Smith ______Oct. 23, 1951 of copper, copper bronze, cuprous chloride, cuprous bromide, cuprous iodide and cupric carbonate. OTHER REFERENCES 3. A process for the preparation of 3-‘chlorodiphenyl Weston et al.: Journal of the American Chemical amine which comprises reacting m-chloroformanilide Society, vol. 50, pp. 859-866 (1928). with bromobenzene in the presence of cupric carbonate 25 Goldberg: Deutsche Chemische Gesellschaft (Berichte), as catalyst and potassium carbonate as acid-acceptor at vol. 40, pp. 4541—4546 (1907).