Amination AND FILM CORPORATION, GRASSELLI, N. P. '1p"r
W o r k published during;the past year Concerning the Bichamp (iron and acid) method of reducing nitro compounds to form amines includes the preparation of several new amines in the aliphatic and aromatic series and the development of a sensitive test for 1 -propoxy-%aminoCnitrobenzene (Ultrasweet) involving Bkchamp reduction to the diamine. Catalytic reduction of nitro compounds to amines included the study of various promoters and activators for Raney nickel and the routine reduction of a large number of nitro compounds of varied structure using generally accepted catalysts and a miscellany of conditions. Electrolytic reduction OF nitro compounds concerned mainly specific conditions for many compounds in weak acid or alkali to give normal amines, in strong acid to give p-hydroxylated amines, and in strong alkali to give hydrazobenzenes that rearrange to benzidines in strong acid. Miscellaneous reductions of nitro compounds involved the reduction of various specific nitro compounds with tin, zinc or aluminum and acid, the reduction of oximes to amines using sodium or sodium amalgam and alcohol, the formation of azowy compounds with alkaline stannite, the simultaneour reduction of nitro and ethylene groups by lithium aluminum hydride, and alkaline oxidation-reduction of 8,4-dinitrotoluene to 2-amino-4-nitrobenzoic acid.
ONSIDERABLE amount of literature concerning the chemical and engineering aspects of amination by reduction has appeared during the past year. The major share of attention concerning this unit process has been directed toward the catalytic approach, particularly on a laboratory scale. Work on the other phases of this unit process has been about evenly divided in scope, except for the increased emphasis on electrolytic reduction, particularly by Indian workers under the leadership of B. B. Dey. This review is divided into BQchamp (iron and dilute acid), catalytic, sulfide, electrolytic, and miscellaneous reductions.
&CHAMP REDUCTION Little has been reported during the past 12 months regarding the industrially well-established BBchamp method. Gold (22) patented the reduction of aliphatic 2-nitrosulfonic acids t o the corresponding amines by means of iron and dilute acid and by catalytic reduction, as with Raiiey nickel. Mohler (36) has devised a practical method of detecting l-propoxy-2-amino-4-nitrobenzene (Ultrasweet) which involves reduction to a diamine by means of ferrous salts and concentrated hydrochloric acid, following by diazotization and coupling, or by oxidation of the diamine to develop a distinctive color. Hodgson and Dean (24) reported the preparation of 8-bromo-2-naphthylamine and 7bromo-1-naphthylamine by reduction of the corresponding nitro compounds with iron and aqueous ferrous sulfate. These compounds may pomibly find use as valuable dye intermediates. Sergievskaya and Levshina (63)described the reduction of 5-nitro-1-naphthalenepropiolicacid with iron in ethyl alcohol containing hydrochloric acid t o give 5-aminonaphthalene-1-propiolic acid.
CATALYTIC REDUCTION Considerable research and development work concerning catalytic reduction of nitro compounds has appeared in the literature during the period covered by this review. Samuelson et al. ( 4 9 ) reported the reduction of various nitro compounds to amines with hydrogen using the following catalysts : Raney nickel, Raney nickel with platinum, Raney nickel in the presence of alkali, and Raney nickel with platinum in the presence of alkali. Their starting materials included mono-, di-, and trinitrated alkanes, benzenes, substituted benzenes, naphthalenes, and anthraquinone. They found t h a t platinum acts as a pro-
moter, generally causing a more rapid hydrogenation. The action of excess alkali is variable, sometimes retarding and sometimes enhancing t h e speed of hydrogenation. Where alkali causes a retarding action, the use of platinum offsets this effect. These workers also found some confirmation of t h e idea t h a t orthosubstituted nitro compounds hydrogenate faster than those substituted in the meta or para positions. Levering et al. ( 2 7 ) have also described various promoters or activators of the more active forms of Raney nickel (such as the W-6 form of the catalyst). They found t h a t platinic chloride, triethylamine plus platinic chloride, and triethylammonium chloroplatinate are in general beneficial in this respect. These workers also developed a rapid method for estimating the amount of nickel in wet Raney nickel catalysts. Various catalytic reductions of aliphatic nitro compounds have been reported during the past year. Lincoln (88) patented the catalytic reduction of ap-dimethyl-p-nitropropionic acid t o the corresponding amine using hydrogen, water, barium hydroxide, and Raney nickel a t 90" 6.and 1400 pounds per square inch gage. Clapp et al. ( 7 ) reported the catalytic reduction of aliphatic monoand dinitro-olefins using Raney nickel, or platinum oxide gives the corresponding amino compounds in varying yields depending on the particular compound involved. Ruoff and Miller (4'7)described the reduction of 2-nitro-2-phenyl-l,3-propanediolt o the amine using 95% ethyl alcohol and Raney nickel a t approximately 1200 pounds per square inch gage. A kinetic analysis of the catalytic reduction of acetoxime t o ispropylamine has been published by Simonetta (54). Lincoln (29) patented the catalytic reduction of aliphatic cyano esters in the presence of formic acid esters and Raney nickel or Raney cobalt to give formylamino esters. Acylation of the amine in situ exerts a protective influence upon it. An interesting patent has been issued to Castle (6) covering the hydrogenation of dicyanobutenes in the presence of alcohols, ammonia, and primary and secondary amines to yield 3-substituted 1,6-hexanediamines. I n general, small amounts of alkali and catalysts such as cobalt are used a t high pressures and moderate temperatures. The 3-substitution is formed by addition of the other compounds across the double bond of the butenes during the reduction. A discussion of catalytic reductive amination of ketones t o primary or secondary amines using Raney nickel has been published by Randvere (48). A great deal of work concerning the various aspects of catalytic reduction of aromatic nitro compounds appeared during t h e past twelve months. Teeters (60) patented a process for the vapor phase hydrogenation of nitroxylene using such catalysts as nickel on pumice at 150 to 200 pounds per square inch gage and 285 C. Longer catalyst life is ensured by prior distillation of the nitroxylene. Houghton and Lowdermilk (26)have also obtained a patent on a similar process which yields xylidine of satisfactory commercial purity without the need of fractionation. In the same field,
1917
1918
INDUSTRIAL AND ENGINEERING CHEMISTRY
a patent has been issued t o hliller ( 9 4 )describing a process for the preparation of gaseous mixtures of hydrogen and nitroxylenc suitable for hydrogenation with nickel catalysts and showing no poisoning effect on the catalysts. Matsukawa et al. (5.9)described the reduction of various chloromethylated nitrobenzene derivatives with palladium and hydrogen t o give the corresponding substituted toluidines. Phillips and Maggiolo (39)reported on the reduction of nitrobenzyl alcohols and nitrobenzaldehydes with Adams platinum oxide catalyst. With alcohols the corresponding amine is formed easily with the meta derivative; the para compound yields a polymer, and with aldehydes, both the meta and para isomers give polymers. The same catalyst gave good yields of 4-amin0-2~3-dihydroxybenzoic acid and 4-amin0-2~5-dihydrobenzoicacid from the corresponding nitro derivatives according t o Bhattacharyya and Seymour (6). Sann% and Lapin (60) published details of a synthesis of p-aminosalicylic acid in an over-all yield of 40 t o 45% from o-nitrophenol. In the first step, o-nitrophenol is reduced with Raney nickel and hydrogen in the presence of acetic anhydride to give 2-methylbenzoxazole. This is then nitrated and hydrolyzed to 2-amino-5-nitrophenol; after diazotization and a Sandmeyer reaction, 2-hydroxy-5-nitrobenzonitrile is formed. The latter is hydrolyzed t o 4-nitrosalicylic acid; this is reduced with hydrogen and Raney nickel t o the desired compound. The synthesis of 4-amino-2,B-dihydroxybenzoicacid and its methyl ester by reduction of the nitro compounds with hydrogen and platinum oxide in the presence of ethyl alcohol has been patented by Rosdahl (45). Tucker (61) described the preparation and use of Raney nickel in the preparation of o-phenylenediamine. Adams and Nagarkatti (1) published details for the synthesis of 2,4- and 2,B-diamino-rn-xylenes from the corresponding dinitro compounds using hydrogen and Raney nickel in ethyl alcohol solution. Similarly, Adams and Nelson ( 2 ) described the preparation of diaminodurene. Moser and Gompf ( 5 7 )reported the reduction of 2-amino-6-nitrobenzoic acid t o form 2,6-diaminobenzoic acid using Raney nickel as a catalyst in methanol. The catalytic hydrogenation of 1,3,5-trinitrobenzene and 2,4,6-trinitroalkylbenzenes to the corresponding triamino derivatives using Raney nickel in ethyl acetate a t low temperatures (30” to 40” C.) has been patented by McLean et al. (81). Miura and Bando (36) described the preparation of 4-aniino-4’-acyIaminodiphenylsulfones from the corresponding 4-nitro derivatives using hydrogen and Raney nickel. Some work has also been carried out on the catalytic reduction of nitro derivatives of heterocylic compounds during the past year. Anderson and Campbell (3) described the preparation of 3-aminocarbazole from 3-nitrocarbazole using hydrogen and platinum oxide in ethyl alcohol solution. Senkus (52) patented the catalytic reduction of nitro-l,3-dioxanes to the corresponding amines in solvents, such as methanol, a t approximately 25” C. and 2000 pounds per square inch gage. SULFIDE REDUCTION Very little new work has been reported on the sulfide method of reduction of nitro compounds. Hey and Osband ( 2 5 ) studied the action of sulfides on several o-nitro-a-phenylcinnamic acids and found that the nitro group reduced smoothly except where the a-phenyl residue possessed a nitro group in the para position. I n this case, the para nitro group was reduced preferentially. Roche Products, Ltd. (43) patented the reduction of 2,4-diamino-3nitropyridine to 2,3,4-triaminopyridine using aqueous sodium sulfide.
ELECTROLYTIC REDUCTION Considerable work on electrolytic reduction of nitro compounds has been published during the past 12 months, particularly by Dey and his coworkers in India. Dey, Maller, and Pai (12) studied the electrolytic reduction of both 0- and m-nitrobenzoic
Vol. 43, No. 9
acids in about 30% sulfuric acid using a copper cathode and lend anode. The ortho acid gives anthranilic and 5-hydroxyanthranilic acids and the para acid yields m-aminobenzoic and 5-aminosalicylic acids. Weber and Meister ( 6 4 ) described a simple set,up for the electrolytic reduction of o-nitrophenol t o o-aminophenol using 3 N sodium hydroxide and iron wire gauze electrodes. A method for the electrolytic reduction of nitrobenzene in 82% sulfuric acid t o give p-aminophenol in good yield and quality has been published by Fujita and Yoshikawa (21). Dey et al. (10) described the preparation o f 2,4-diaminophenol in nearly 50% yield by electrolyzing a n emulsion of nL-dinitrobenzene in 40% sulfuric acid and using a copper or Monel cathode, a temperature of 95” C., and a current density of 5 to 7 amp. per square dm. Dey and his coworkers obtained patents on the preparation of 2,4-diaminophenol by electrolytic reduction of 2,4-dinitrophcnol in 3Oy0 sulfuric acid a t a copper cathode ( I S ) , the formation of the same product by electrolyzing rn-nitroaniline in 40% sulfuric acid a t a copper cathode in the presence of copper sulfate (f?), and the electrolytic reduction of o-nitrotoluene and m-nitrotoluene in 30y0 sulfuric acid a t an amalgamated Monel cathode in the presence of copper sulfate to give 4-amino-m-cresol in 46% yield and 4-amino-0-cresol in 5570 yield, respectively (14, f5). Dey (11)also patented the electrolysis of nL-nitroaniline in 30% sulfuric acid a t a Monel cathode with a trace of mercuric sulfate a t a current density of 2.3 amp. per square dm. to give 2,4-diaminophenol. During the period covered by this review, three Indian patents have been issued t o Dey and coworkers on the electrolytic reduction of nitro compounds in alkaline medium to give hydrazobenzenes which can be rearrungcd to benzidines in the presence of strong acid. The latter are, in general, vduable dye intermediates. The first of thesc patents ( 8 ) concerns the electrolj-sis of o-chloronitrobenzene in 10% sodium hydroside in the prcsetice of lead oxide an an iron cathode and a current density oi 2 amp. per square dm. t~o give 2,2’-dichloroh~.tlrazobenzene, which rearranges to 3,3‘-dichlorobenaidirle in the presence of sulfuric arid. The second (9) covers the olectrolytic reduction of 2,5-dichloronitrobenzene in 2 t o 40% sodium hydroxide at a cathode of nickel, iron, lead, or Moncl and a current density of 0.5 to 10 amp. per square dm. t o give 2,2’,5,5’-tetrachlorohydrazobenzcne, which rearranges t o 2,2’,5,5’-tetrachlorobenzidirieon treatment with sulfuric acid. The third patent (16) concerns the electrolysis of 4-chloro-2-nitrophenetole in 10% sodium hydroxide in the prcsence of lead oxide a t a n iron cathode and a current density of 2 amp. per square din. to 5,5’-dichloro-2,2’-diethosyhydrazobenzene, which forms 6,6’-dichloro-3,3’-diethoxybenzidinehen boiled with concentrated hydrochloric acid. Seagers and Elving (51 ) found t h a t hydro~ynitrobut,ariesivith hydroxyl and nitro groups on adjacent carbon atoms are polarographically reduced t o hydrosyalkylh\drox~~lamincsi n itridic medium. Although in alkaline solution, conversion to the nonreducible ion of the acid form generally takes place, there is some evidence t h a t 1-nitro-2-butanol reduces to the aminc under alkaline conditions. StoEesovB (58) has reported t h a t nitrolmizene, m-nitrophenol and 0- and p-nitroanisole are reduced to tho corresponding amine in two steps at the dropping mercury elcc~trode, the first stage being the hydroxylamine, whereas p-nitrophcnol and p-nitroaniline proceed in one step.
MISCELLANEOUS REDUCTIONS Among the miscellaneous reduction methods studied during the period covered by this review may be mentioned tin, zinc or aluminum and acid, sodium and alcohol, alkaline stannite, sodium amalgam, lithium aluminum hydride, and alkaline osidationreduction. Vanderzee and Edgell (62) published a method for dctcrniination of aromatic nitro compounds with tin, hydrochloric acid, and methanol, by weighing the amount of tin lost. T h e same authors (63)also made a considerable study of the reduction kinetics of aromatic nitro components with tin and hydrochloric &id. Fon-
September 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
taine and Teh-Fu Pan (80)described the preparation of p-aminosalicylic acid from the corresponding nitro compound by means of t,in and concentrated hydrochloric acid in very high yield. Hsn and Teh-Fu Pan (26) have similarly given a process for the synthesis of p-hydroxyanthranilic acid from the corresponding nitro compound by means of tin and acid. hIatsui (S2) published directions for reducing m-nitrostyrene to m-aminostyrene by using tin and acid. Takubo (59) described the reduction of 4-nitro3',5'-dibromobipheny1~;ulfonicacid, and Stauble (56) has given a process for the reduction of 5-nitrobenzimidazole, both by the same method. Simons ( 5 5 ) reported the reduction of nitrocyanoacetic esters and nitromalonic esters wit,h zinc, a trace of copper, acetic acid, and acetic anhydride to give acetylamino compounds. Bean ( 4 ) has patented the reduction of nitrobenzene and its derivatives not subst,ituted in the para position to form p-aniinophenols by reaction with aluminum and an aqueous solution of an organic acid at, 80' to 100" C. Prelog et al. ( 4 0 ) have described the synthesis of cycloalkylamines with rings containing six to eighteen carbon atoms, by reduction of the corresponding oximes with sodium and ethyl alcohol. Neish (38)has similarly reported the smooth reduction of 2- and 3-methoxy-9-fluorenone oximes with sodium amalgam in ethyl alcohol to the corresponding amines. Lukashevich (SO) has described the smooth formation of azoxy compounds from the corresponding nitro derivatives by means of 1.5 moles alkaline stannit,e solution. A Dutch patent (18) has been issued concerning the continuous tower reduction of nitrobenzene t o hydrazobenzene using sodium amalgam in 70% ethyl alcohol with iron salts and carbon (or graphite) as accelerators. Erne and Ramirez (19) published an interesting method of producing p-phenylethylamines t h a t involves reduction of p-nitrostyrenes using lithium aluminum hydride. Ramirez and Burger (41 ) described the preparation of hydrosy- and methoxyphenylethylamines by the same method. Rosdahl ( 4 6 ) patented the preparation of 2-amino-4-nitrobenzoic acid by the oxidative-reductive action of alkali on 2,4-dinitrotoluene. This type of reaction, which is interesting and unusual, appears t o offer decided economic advantages in the synthesis of aminobenzoic acids. However, the yields are generally of a magnitude of low order, offsetting t o a large extent the low cost of starting materials and low operating expenses. Several miscellaneous items concerning amination by reduction have appeared during the past year. A patent ;Pas issued to Starr and Ratliff (57) covering the stabilization of color in xylidine by using very small concentrations of aliphatic amines. Rogers (44)patented the stabilization of aromatic amines toward heat, light, and oxidation by treatment with metal halides, followed by alkali treatment and then distillation. Sakuyama (48) determined vapor-liquid equilibrium data for nitrobenzene and aniline and concluded they do not form an azeotrope.
LITERATURE CITED Adams, R., and Nagarkatti, A. S.,J. Am. Chem. SOC.,72, 1831-2 (1953). Adams, R., and Nelson, N. K., Ihid., 72, 132-5 (1950). Anderson, C., and Campbell, N., J . Chem. SOC.,1950, 2904-5. Bean, F. R. (to Eastman Kodak Co.), U. S. Patent 2,525,515 (Oct. 10, 1950). Bhattacharyya, S. C., and Seymour, D. E., J . Chem. Soc., 1950, 1139-40. Castle, J. E. (to E. I. du Pont de Kemours and Co.), U . S. Patent 2,532,277 (Dee. 5, 1950). Clapp, L. B., Brown, J. F., Jr., and Zeftel, L., J . Org. Chem., 15, 1943-7 (1950). Dey, B. B., Govindachari, R., and Rajagopalan, 8. C., Ibid., 34,756 (July 28, 1948). Ibid., 34,757 (July 28, 1948). Dey, B. B., Govindachari, R. and Venkatakrisna, H., Ibid., 36,328 (Dec. 1, 1948). Dey, B. R., Indian Patent 37,566 (Jan. 12, 1949). Dey, B. B., Maller, R. K., and Pai, R. R., J . Sci. I n d . Research ( I n d i a ) ,9B, No. 3, 55-7 (1950).
1919
Ibid., Indian Patent 39,427 (Fcb. 1, 1950) I b i d . , 39,428 (Feb. 1, 1950). Ibid., 39,429 (Feb. 1 , 1950). Ibid., 40,261 (March 1, 1950). Dey, R. B., hlaller, R. K., Pai, B. R., and Udupa, €I. V., Ibid., 39,426 (Feb. 1 , 1950). (18) Directie van de Staatsmijrien in Limbuw. - Dutch Patent 66.462 (Sept. 15, 1950). Erne, hl., and Ramirez, F., Helc. Chim A c t a , 33, 912-16 (1950). Fontaine, D . , and Teh-Fu Pan, W., Sciencr and Technol. China, 1, 111 (1948). Fujita, A , , and Yoshikawa, T., J . Pharm. Soc. J a p a n , 70, 209-12 ( 1950). Gold, &I. H. (to Visking Corp.), C , S. Patents 2,510,281, 2,510,282 (June 6, 1950). Hey, D. H . , and Osband, J. M., J . Chem. SOC.,1949, 3184-71. Hodgson, H. H., and Dean, R. E., I b i d . , 1950, 818 -20. Houghton, 9.S., and Lowdermilk, F. R. (to Allied Chemical and Dye Corp.), C . S. Patent 2,499,918 (March 7 , 1950). Hsu, C., and Teh-Fu Pan, W., Science and Technol. China, 2,31-2 (1949). Levering, D. R.,Morrits, F. L., and Lieber, E., J . Am. Ciiem. SOC.,72, 1190-4 (1950). Lincoln, J. (to Celanese Corp. of America), U. S. Patent 2,501,825 (March 28, 1950). Ibid., 2,514,549 (July 11, 1950). Lukashevich, V. O., Doklady A k a d . ;\'auk S.S.S.R., 57, 907-10 (1947). McLean, A., Tetlow, W. E., and Munro, J. (to Imperial Chemical Industries, Ltd.), U. S.Patent 2,501,907 (March 28, 1950). Matsui, E., J . SOC. Chem. Ind., J a p a n , 45, Suppl. Binding, 438 (1942). Matsukawa, T., Matsuno, T., and Shirakawa, K., J . Pharni. SOC.J a p a n , 63, 1-5 (1943). Miller, 8.P. (to Allied Chemical and Dye Corp.), U. S. Patent 2,507,539 (May 16, 1950). Miura. K., and Bando, Y., J . Pharm. Soc. J a p a n , 63, 75-8 (1943). Mohler, K., 2. Lebensm.-Untersz~ch,21. -Forsch., 91, 124-6 (1050). Moser, C. M., and Gompf, T., J . Qrg. Citem., 15, 683--6 (1850). Neish, W. J. P., Rec. trav. chim., 69, 207-19 (1950) Phillips, A. P., and Maggiolo, A , , J . Q,g. Chem., 15, 659-61 (1950). Prelog, V., El Neweihyt, M. F., and Hifliger, N e h . Chim. Acta, 33, 365--9 (1950). Ramirez, F. A , , and Burger, A , , J . Ani. Chem. Noc., 72, 2781-2 (1950). Randvere, F., Anales f a r m M bioquinz. (Buznos Aires), 19, 81-5 (1948). Roche Products, Ltd., Brit. Patent 629,439 (Sept. 20, 1949). Rogers, D. T. (to Standard Oil Development Co.), U. S. Patent 2,512,504 (June 20, 1950). Rosdahl, K. G . (to Aktieselskabet "Ferrosan") , Swed. Patent 127,434 (Feb. 21, 1950). Ibid., 128,380 (June 6 , 1950). Ruoff, P. M . , and Miller, J. R., J . A m . Chem. Soc., 72, 141719 (1950). Sakuyama, S., J . Soe. C h i m . I n d . , J a p a n , 44, Suppl. Binding, 266-7 (1941). Samuelson, G. S., Garik, V. L., and Smith, G. B., J . Am. Chem. SOC.,72,3872-4 (1950). SanniB, C., and Lapin, H., Bull. soc. chim. France, 1950, 322-6. Seagers, W ,J., and Elving, P. L., J. A m . Chern. Soc., 72, 3241-3 (1950). Senkus, .Mi. (to Commercial Solvents Corp.), V. 8. Patent 2,485,987 (Oct. 25, 1949). Sergievskaya, S. I., and Levshina, K. V., J . G e n . Chem., 20, 1481-6 (1950). Simonetta, M., Chimica e industria (Milan), 29, 267-70 (194;). Simons, C., J . Chem. Soc., 1950, 2392-3. Stauble, M., Hela. C h i m . Acta, 32, 135--45 (1949). Starr, C . E . , Jr., and Ratliff, F. T. (to Standard Oil Dcvelopment Co.), U. s. Patent 2,509,891 (May 30, 1950). StoEesovB, D., Collection Czechoslan. ('hem. C o m m u n s . , 14, 615-25 (1949). Takubo, T., J . P h a r m . Sac. J a p a n , 63,475--7 (1943). Teeters, W. 0 . (to Allied Chemical and Dye Corp.), U. S.Patent 2,526,913 (Oct. 24, 1950). Tucker, S.H., J. Chem. B!ducation, 24, 489-93 (1950). Vanderzee, C. E., and Edgell, \Vs Y., A n a l . Chem., 22, 572-4 (1950). Vanderz'ee, C. E., and Edgell, W. I?., J . Am. Chem. Soc., 72, 2916-23 (1950). Weber, J. E., and hleister, A. E., J . Chem. Education, 27, 571 (1950). R E C E I V E.June D 17, 1951. (13) (14) (15) (16) (1T)
