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.