Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C213/00—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton
  • C07C213/02—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton by reactions involving the formation of amino groups from compounds containing hydroxy groups or etherified or esterified hydroxy groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C217/00—Compounds containing amino and etherified hydroxy groups bound to the same carbon skeleton
  • C07C217/78—Compounds containing amino and etherified hydroxy groups bound to the same carbon skeleton having amino groups and etherified hydroxy groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton
  • C07C217/80—Compounds containing amino and etherified hydroxy groups bound to the same carbon skeleton having amino groups and etherified hydroxy groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton having amino groups and etherified hydroxy groups bound to carbon atoms of non-condensed six-membered aromatic rings
  • C07C217/82—Compounds containing amino and etherified hydroxy groups bound to the same carbon skeleton having amino groups and etherified hydroxy groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton having amino groups and etherified hydroxy groups bound to carbon atoms of non-condensed six-membered aromatic rings of the same non-condensed six-membered aromatic ring
  • C07C217/90—Compounds containing amino and etherified hydroxy groups bound to the same carbon skeleton having amino groups and etherified hydroxy groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton having amino groups and etherified hydroxy groups bound to carbon atoms of non-condensed six-membered aromatic rings of the same non-condensed six-membered aromatic ring the oxygen atom of at least one of the etherified hydroxy groups being further bound to a carbon atom of a six-membered aromatic ring, e.g. amino-diphenylethers

Definitions

• the invention relates to a process for the preparation of halogenated aromatic amines, optionally also containing an ether linkage, e.g., triclosan amine (5-chloro-2-(2,4- dichlorophenoxy)aniline), by catalytic hydrogenation of the corresponding halogenated aromatic nitro compounds with ammonium formate in the presence of noble metal catalysts, such as platinum supported on carbon.
• an ether linkage e.g., triclosan amine (5-chloro-2-(2,4- dichlorophenoxy)aniline)
• Chlorinated aromatic amines are important intermediates in the manufacture of dyestuffs and pigments.
• Halogenated amino diphenyl ethers form an important class of intermediates for the preparation of halogenated hydroxy diphenyl ethers useful as antimicrobial agents, e.g., triclosan.
• Hydrogenation/reduction of aromatic nitro compounds to the corresponding aromatic amines is known to be one of the-most facile transformations.
• Several processes have been described in the literature for the said hydrogenation employing catalytic hydrogen transfer, that is, without using external hydrogen; as well as catalytic hydrogenations at elevated hydrogen pressures in the presence of noble metal catalysts, such as, platinum, palladium, ruthenium, rhodium iridium, etc. on various supports and Raney nickel catalysts.
• halogen substituted aminoaryl ethers are extremely susceptible to two types of hydrogenolysis side reactions, one involving the C-X (where, X represents F-, Cl-, Br- and I-) bonds (dehalogenation) and the other involving the C-O-C bonds (ether cleavage).
• halonitrodiarylether is 5-chloro-2-(2,4-dichlorophenoxy)nitrobenzene, which is hydrogenated to yield 5-chloro-2-(2,4-dichlorophenoxy)aniline, commonly known as TADE (trichloroaminodiphenylether), which is an intermediate in the production of a widely used antimicrobial agent, triclosan.
• TADE trichloroaminodiphenylether
• US5041671 recommends the use of sulfited and sulfided platinum orr carbon as catalysts for the selective hydrogenation of 4-chloro-2,5-dimethoxynitrobenzene, in the presence of 1 °, 2° and 3° amines and compounds, which produce a pH of 8-10 in aqueous solutions
• US4059627 recommends use of thioethers during the hydrogenation with platinum on carbon along with compounds giving pH of 7-9
• US3073865 recommends magnesite (MgO) as an additive
• US3149161 recommends sodium acetate as an additive
• US3546297 recommends ammonia, morpholine derivatives (0.01 - 1.5 mole per mole of substrate) and Ni, Cr ions (5-500ppm based on the substrate) as additives
• US4059627 recommends the use of thioethers and compounds giving a pH of
• the metals are required to be employed in more than stoichiometric amounts
• the hydrogen doner compound is needed in stiochiometric excess to achieve quantitative yields and the unconsumed donor compound also needs to be separated from the producl, 4.
• the throughput of the process is substantially low as a result of the inclusion of the hydrogen donor compound and the solvent in the reaction mass, and
• Still another problem that needs to be considered is that the erosion of the reactors used for these reactions occurs due to the metal particles during agitation, giving rise to potentially unsafe conditions. The reactors thus need to be replaced frequently.
• Another object of the present invention is to provide a process, which combines the beneficial aspects of both catalytic hydrogen transfer and classical catalytic hydrogenation using gaseous hydrogen.
• Still further object of the present invention is to provide a process, which is economically viable.
• Halonitroarenes are partially reduced by catalytic transfer hydrogenation "with ammonium formate (O.Olmole per mole to 2mole per mole of the substrate) as a s hydrogen source in the presence.of 0.01% to 2% (based on the substrate) platinum based catalysts at ambient to 150 0 C and the hydrogenation is completed by introducing hydrogen to the autoclave from 0kg/cm2 to 50kg/cm2 « Catalytic transfer hydrogenation with ammonium formate or high pressure catalytic hydrogenation in the absence of ammonium formate, when used alone with platinum based catalysts, result in lower purity of the corresponding amines as a result of hydrogenolysis of the C-CI (where, X represents F-, CI-, Br- and I) and the C-O-C bonds.
• the hydrogenation can be carried out either by using water as a solvent or lower quantity of solvent wherever required.
• a process for the preparation of 5-chloro-2-(2,4-dichlorophenoxy)aniline which process is completed by carrying out reduction of an aromatic halo nitro compound, such as 5-chloro-2-(2,4-dichlorophenoxy)nitrobenzene and the like, using a combination of hydrogenations, such as catalytic transfer hydrogenation , followed by gaseous hydrogenation, using an effective amount of an appropriate catalytic transfer hydrogenating agent, such as ammonium formate and the like, and an effective amount of an appropriate catalyst, such as platinum on carbon and the like.
• a process wherein said catalytic transfer hydrogenation followed by gaseous hydrogenation, comprises the steps of: a. charging to an autoclave a predetermined amount of a nitroether, such as 5-chloro-2-(2,4-dichlorophenoxy)nitrobenzene, the effective amount of said ammonium formate being from 0.01 to 2 mol / mol of said nitroether, said appropriate catalyst being any one catalyst selected from the group consisting of an untreated platinum on carbon, a sulphite ⁇ platinum on carbon and a sulphided platinum on carbon, wherein said effective amount of 1 said catalyst is from 0.01 % to 2 % w/w of said nitroether, with said catalyst having the amount of platinum content 0.1 % to 5% w/w of said catalyst, and an effective amount of any one solvent selected from the group consisting of alcohol and water, wherein ratio of said nitroether to said solvent is from 1 :0.1 to 1 :0.33w/w; b.
• a nitroether such as 5-
• step b carrying out, after said period of reaction of step b is completed, the reaction of said gaseous hydrogenation, at a pressure between 1 to 50 kg/cm 2 , by introducing in said autoclave external hydrogen gas, till hydrogen up - take ceases; d. isolating said 5-chloro-2-(2,4-dichlorophenoxy)aniline.
• said catalyst is said sulphited platinum on carbon.
• the present invention is a method of hydrogenating halonitro compounds using CTH agents, which function not only as a hydrogen source but also help in controlling the formation of impurities, such as, dehalogenation and ether cleavage impurities.
• the said agent can effectively be used with any type of platinum based catalysts.
• the current inventive process can be employed for the said reduction process using even untreated platinum on carbon catalyst, with high selectivity.
• the process of the present invention does not use any additive, which is basic in nature.
• reaction mass was cooled to room temperature and the autoclave was purged with nitrogen. Unconverted NE could be seen as solids in the reaction mass. Therefore, the reaction mass was filtered using toluene and the organic layer was separated from the aqueous layer. The organic layer was distilled to remove the solvents and the product mixture was analysed by GC. The conversion of NE and percent selectivity towards TADE obtained was surprisingly found to be only 29.52% and 97.53%, respectively. The reaction also resulted in the formation of high levels of DCP, which was about 1.42%.
• reaction mass was cooled to room temperature and the autoclave was purged with nitrogen. Unconverted NE could be seen as solids in the reaction mass. Therefore, the reaction mass was filtered using toluene and the organic layer was separated from the aqueous layer. The organic layer was distilled to remove the solvents and the product mixture was analysed by GC. The conversion of NE was found to be low even in this case (35.59%) and percent selectivity towards TADE obtained was found to be 98.93%. The formation of DCP was found to be 0.03% in the reaction mass and the dehalogenation amounted to 0.34%. EXAMPLE 5.
• NE (20Og, 628mmol), 3% Pt/C (PMC Monarch 203) (0.8g, 0.4% w/w based on NE) and water (20Og) were charged to the autoclave.
• the reaction was continued at 30kg/cm2 pressure at 85°C till the hydrogen up-take ce'ased, which took 2 hour.
• reaction mass was cooled to room temperature, hydrogen vented and the autoclave was purged with nitrogen.
• the reaction mass was filtered and the organic layer was separated from the aqueous layer.
• the organic layer distilled to remove the solvent and the product mixture was analysed by GC.
• the conversion of NE and percent selectivity towards TADE obtained was found to be 99.33% and 99.77%, respectively.
• the formation of DCP was found to be 0.07% in the reaction mass and the dehalogenation amounted to 0.04%.
• the conversion of NE and percent selectivity towards TADE obtained was found to be 99.12% and 99.55%, respectively.
• the formation of DCP was found to be 0.15% in the reaction mass and the dehalogenation amounted to 0.06%.
• reaction mass was cooled to room temperature and the autoclave was purged with nitrogen. Unconverted NE could be seen as solids in the reaction mass. Therefore, he reaction mass was filtered using toluene and the organic layer was separated from the aqueous layer. The organic layer distilled to remove the solvents and the product mixture was analysed by GC. The conversion of NE and percent selectivity towards TADE obtained was found to be 53.70% and 97.20%, respectively. The formation of DCP was found to be 1.36% in the reaction mass and the dehalogenation amounted to 0.46%.
• reaction mass is cooled to 130 0 C and second lot of water is added which is followed by 10% sodium hydroxide solution and the third' lot of water.
• the heterogeneous mass thus obtained is then cooled to room temperature and filtered to separate 5-chloro-2-(2,4-dichlorophenoxy)nitrobenzene from aqueous salt solution.
• the solid is then washed with water till the washings are free from sodium, potassium or chldride ions.
• the yield of 5-chloro-2-(2.4- dichlorophenoxy)nitrobenzene thus obtained is 95% based on the 2,5 dichloronitrobenzene charged and purity was 99.54%.

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