ELECTROCHEMICAL SYNTHESIS OF SUBSTITUTED AMINES IN BASIC MEDIA.

This invention relates to the preparation of substituted aromatic amines. More specifically, it pertains to a process for the electrolytic reduction of substituted nitro aromatic compounds to produce their corresponding amines.

Of the substituted aromatic amines, aminohy¬ droxybenzoic acids are known to be useful as monomers in the preparation of polybenzoxazoles. Polybenzoxa- zoles can be prepared by the condensation of certain multifunctional aromatic compounds such as the amino¬ hydroxybenzoic acids of the present invention. Poly- benzoxazole fibers have high tensile and compressive strengths and thermal stability and are desirable for military, aerospace and other applications requiring rigid materials.

The reduction of nitro aromatic compounds to their corresponding amines is well-known. For example, U.S. Patent 3,475,299 describes an electrolytic reduc¬ tion of a nitro aromatic compound in an acidic medium in the presence of hydrogen sulfide. U.S. Patent 3. -42*4,659 discloses a process for electrolytically

reducing nitro aromatic compounds in an electrolytic cell with an acidic catholyte and a basic anolyte. U.S. Patent 3,475,300 describes a process for reducing nitro aromatic compounds in the presence of sulfuric acid.

All of the above processes relate to an electrolytic reduction in acidic medium. The acidic environment of the aforementioned processes may induce a Bamberger type rearrangement of reaction intermedi¬ ates, especially at elevated temperatures. The acidic medium makes aromatic compounds susceptible to nucleo- philic attack by moieties present in the solution such as water. Therefore, the presence of an acidic medium may lead to the formation of undesirable by-products if direct reduction of the nitro aromatic compound to its corresponding amine is desired. Thus, the selectivity of the electrolytic reduction is decreased.

The limited electrolytic reduction of nitro aromatic compounds in the presence of base has been previously described. For example, Brown and Warner, J. Phys. Chem. , 27, 455-465 (1923) describe the reduction of o-nitrophenol by electrolysis to o-amidophenol. Probably o-aminophenol was intended in an alkaline medium in the presence of various metals such as zinc, lead and copper as the cathodic material. Belot et al., Tetrahedron Letters , Vol. 25, No. 47, 5347-5350 (1984) disclose the electrocatalytic hydrogenation of nitro compounds to amines in an alkaline medium in the presence of Devarda copper and Raney nickel electrodes. Belot et al. teach that the reduction is very ineffi¬ cient and produces unwanted azobenzene when a conven¬ tional copper electrode is employed. Organic Electrochem¬ istry , M. M. Baizer & H. Lund, 2nd Ed., Marcel Dekker,

Inc, 295-313 (1983) teaches that the electrolytic reduction of various nitro aromatic compounds in an alkaline medium most often yields dimers and other coupled products.

An electrolytic process is needed that would provide for the selective reduction of functionalized nitro aromatic compounds in basic media to their cor¬ responding amines. A process is also needed that would provide a high current efficiency and thereby minimize the amount of power consumed by the reaction.

The ^" present invention is such a process for the preparation of a substituted aromatic amine comprising electrolytically reducing a substituted nitro aromatic compound in an alkaline medium at a temperature less than 60°C and a current density of at least 50 milli- amps/square centimeter. The process of the present invention preferably yields at least 50 percent of the desired amine.

Contrary to teaching of the prior art, the process of the present invention when carried out in an alkaline medium and in the presence of a copper cathode is very selective for the reduction of several substi¬ tuted nitro aromatic compounds to their corresponding amines. Surprisingly, this process enables the high conversion of nitro group to amino group with very little, if any, dimer products such as azo compounds or hydroxylated products. Further advantages of the process of this invention include ( 1 ) non-corrosive basic medium, (2) lower cell voltage and lower overall voltage requirements, (3) easier separation or isola¬ tion and recovery of products, (4) less electrode foul¬ ing and (5) lower temperature operation. In addition,

this process enables the use of high current densities with minimal evolution of hydrogen. As a result of these advantages, this process is a very efficient and economical method for the selective conversion of nitro aromatic compounds to aromatic amines.

The substituted nitro aromatic compounds suit¬ ably converted to their corresponding amines in the practice of this invention are those nitroaromatic compounds having at least one electron-releasing ring substituent. Preferably, the nitro compound is one represented by the formula:

(Z)m

wherein Ar is an aromatic ring structure, each R is independently hydrogen, alkyl or haloalkyl, each Z is independently an electron-releasing substituent in a position ortho or para to a nitro group, Y is carboxy, sulfo, cyano, carboxylate ester, aryl, and halo, m is an integer from 1 to 5, p is 0 or 1, n is an integer from 1 to 3 and o is an integer representing the remaining positions available for substitution on the aromatic ring structure.

For the purposes of this invention, an "aro¬ matic ring structure" is one having one or more carbo- cyclic and/or heterocyclic aromatic rings which may be singular or fused multiple rings or non-fused multiple rings bonded directly as in the case of biphenyl or

indirectly through non-aromatic groups such as alkyl- idene, e.g., as in bisphenol A or a heteroatom, e.g., as in diphenyl oxide. Examples of such aromatic ring structures include benzene, naphthalene, pyridine, furan, biphenyl, diphenyl oxide, and diphenyl alkyli- dene such as 2,2-diphenylpropane, with benzene being the most preferred.

Exemplary electron-releasing substituents (Z) include hydroxy, alkoxy and mercapto, with hydroxy

10 being most preferred. Of the Y substituents, carboxy and halo are more preferred with carboxy being most preferred. Examples of R include hydrogen and alkyl, particularly those having from 1 to 4 carbons, with - m hydrogen and methyl being preferred and hydrogen being most preferred.

Examples of preferred substituted nitro aro¬ matic compounds include 3-nitro-4-hydroxybenzoic acid, 0 3-hydroxy-4-nitrobenzoic acid, 2-hydroxy-5-nitrobenzoic acid, 2-nitrophenol, 4-nitrophenol, 2-nitroanisole, 4-nitroanisole, 4-methyl-2-nitrophenol, 2-methyl-3- -nitrophenol, 3-methyl-4-nitrophenol, 5-methyl-2- -nitrophenol, 4-nitrophenetole and nitrotoluene. Of 5 these nitro compounds, the nitro hydroxybenzoic acids are more preferred, with 3-nitro-4-hydroxybenzoic acid being most preferred.

In the practice of this invention, any electro- 0 lytic cell which permits the reduction of a nitro com¬ pound to an amine under alkaline conditions is suit¬ able. The preferred electrolytic cell includes (1) a cathode of copper or similar metal which does not cor¬ rode signi icantly during the reduction process, (2) an anode of nickel, (3) a basic aqueous medium having a pH

greater than 7, preferably greater than 8, and a means for separating the cathode from the anode. Most preferably, the electrolytic cell has a two-chamber design.

The cathode suitably comprises a conductive material which is inert in the alkaline medium under the conditions of the process. Preferably, the conduc¬ tive material is a non-corrosive metal such as copper, stainless steel or nickel, with copper being most pre¬ ferred. The conductive material used for the cathode can also be a conductive carbon-containing material such as graphite, glassy carbon and reticulated vitreous carbon.

The anode can be comprised of any stable con¬ ductor which is capable of generating oxygen in basic conditions. Typical anodic materials include ruthenium on titanium, platinum, palladium and nickel, with nickel being most preferred.

In addition, it is possible and sometimes pre¬ ferred to simultaneously oxidize an organic compound at the anode as in a "paired reaction". Thus, while the desired amine is being produced at the cathode, another organic compound such as nitrotoluene is being oxidized to nitrobenzoic acid at the anode.

The separation means used to define the catho- lyte and anolyte of the electrolytic cell can be any material which will enable the conductance of a current via ion transport through the material. Typical sepa¬ rators include cation- and anion-exchange membranes, diaphragms such as a porous unglazed cylinder or a sin- tered-glass diaphragm, glass frits, and other porous

materials like clay. The separator is preferably com¬ posed of an ion exchange membrane. Most preferably, the separator is composed of a cation-exchange mem¬ brane.

The alkaline medium employed in the process of this invention is preferably a liquid medium having a pH of at least 8. The medium comprises a compound cap¬ able of acting as the electrolyte in the electrolytic cell. For the purposes of this invention, an electro¬

10 lyte is a compound which dissociates in solution and provides an electrically conductive medium. Prefer¬ ably, the electrolyte is a base such as alkali or alkaline earth metal hydroxides, quaternary ammonium _. _£ . hydroxides, ammonium hydroxide, borates, and carbon¬ ates. More preferred bases include alkali metal hydroxides with sodium hydroxide being most preferred.

The solvent for the electrolyte is suitably any 0 liquid having a dielectric constant of at least 10 and being capable of dissolving at least 0.4 weight percent of the electrolyte. Preferably, the solvent is water, a polar organic liquid such as alcohol, lower alkyl nitriles such as acetonitrile, lower alkyl amides such 5 as dimethylformamide, cyclic ethers such as tetrahydro- furan and mixtures of water and one or more of such polar organic liquids. More preferred solvents are water and alcohols such as methanol and ethanol and mixtures of water and such alcohols, with water being 0 the most preferred. Thus, the more preferred alkaline media are aqueous and alcoholic solutions containing from 0.4 to 40 weight percent of dissolved alkali metal hydroxide or alkaline earth hydroxide. Most preferred are aqueous solutions of from 4 to 20 weight percent of an alkali metal hydroxide, especially sodium hydroxide.

Such alkaline media preferably have pH values in the range from 14 to 15, most preferably 14.

The process is suitably practiced by dispersing the substituted nitro aromatic compound in the alkaline medium in the electrolytic cell in proportions suffi¬ cient to permit the desired reduction to occur at a reasonable rate. Preferably, the nitro compound is present in the- catholyte in a concentration in the range from 0.05 to 1, more preferably from 0.25 to 0.75, moles per liter of catholyte.

The current passed through the electrolytic cell is that which is sufficient to provide a desired rate of reduction of the nitro compound to its corre¬ sponding amine. Normally, such current is expressed as current density which is defined herein as the number of coulombs per second passing through a given area (cm ^** -) of the cathode surface. Preferably, the current density employed in the process of the present inven¬ tion is in the range of from 50 milliamperes/square centimeter (mA/cm ² ) to 300 mA/cm ² . The current density is more preferably in the range from 75 to 250 mA/cm ² , with an average current density from 100 to 150 mA/cm ² being most preferred.

This process can be carried out in a continuous or batchwise manner.

The reaction temperature in the electrolytic reduction of this invention is less than 60°C. For example, the electrolytic reduction is preferably performed at 0°C to 60°C, more preferably from 17°C to 30°C. For the electrolysis of some compounds, higher temperatures cause undesirable side reactions and the

decomposition of the nitro aromatic compound or the amine product. The electrolytic reduction of this invention is most preferably carried out at ambient temperatures.

The reaction times depend upon the quantity of the starting material, the current density, the electrode area, and the current efficiency for conver¬ sion. The end point of the reaction is generally the point when the nitro compound is consumed. For example, the end point may be found by monitoring the reaction by high performance liquid chromatography.

In a preferred embodiment, the process of this invention is carried out by electrolytic reduction of the starting nitro aromatic compound under basic condition using copper as the cathode. In this embodiment, an organic solvent may be added to the cathode chamber if the nitro compound is insoluble or only slightly soluble in water. The organic solvent used for this purpose should be an inert organic sol¬ vent which is miscible with water and dissolves the nitro compound. An example of such a solvent or cosol- vent is an alcohol such as methanol, ethanol, etc. It is desirable that a blanket of nitrogen or other inert gas be employed in the electrolytic cell to prevent reoxidation of the amine product.

The process of the present invention surpris- ingly exhibits high current efficiencies and selectiv- ities at high current density. Low power consumption is characteristic of the process of the present inven¬ tion. Therefore, the present invention provides for an economic means for producing substituted aromatic amines, particularly the aminohydroxybenzoic acids

which may be used as monomers in the production of polybenzoxazoles as hereinbefore described.

The following examples are included for the purposes of illustration only. Unless otherwise indicated, all parts and percentages are by weight.

Example 1

In order to investigate the effect of various parameters on the reduction of 3-amino-4-hydroxybenzoic acid, an all-glass, two-chamber, flange-type cell was constructed which allowed easy disassembly and short electrolysis times. The catholyte and anolyte reser¬ voirs were 30 ml capacity with water jacketing for tem- perature control. Convection was achieved via 2 sparge through the bottom of each compartment. Mass transport was not ideal in this cell, but parameter evaluation could be done in an efficient manner with it. The electrodes were approximately 6 cm ² and current densities were reported below for the actual geometric areas. An ion-exchange membrane (typically Nafion 324 ^® obtained from duPont) was pressed between gaskets to expose 6 cm ² area. A 14/20 ground-glass joint on top of each chamber allowed for a condenser and/or an oil-filled 'bubbler' to keep a nitrogen head over the easily oxidized amine. The electrode to electrode separation was about 2.5 cm.

Example la:

As an initial experiment, the following standard conditions were utilized. The cathode was a flag of 99.9 percent copper (6.3 cm ² ) and the anode a

nickel expanded metal flag of equal projected area. The anolyte and catholyte were separated by a cation- -exchange membrane having an exposed area of 6.3 cm ² . The catholyte was composed of 1 g of 3-nitro-4-hydroxy- benzoic acid dissolved in 20 ml of 1N NaOH (initial pH 13-14). The anolyte consisted of 20-25 ml of 5N NaOH. The reaction temperature was maintained at 25 (+1)°C in this example.

A constant current of 0.500 amps (i.e., current 0 density of 79.4 mA/cm ² ) was applied through the cell after nitrogen sparging the cell for 5 minutes. Nitrogen sparge was continuously applied for mixing the catholyte and anolyte. Liquid chromatographic analyses 5 were performed throughout the run on aliquots of the catholyte to follow the course of the reaction. The theoretical charge for conversion of the starting material to the amine was calculated as

₀ Q _t = (solute(g)/183g/mole) x (96485C/eq) x (6eq/mole).

The chemical yield, current efficiency (CE), and con¬ version were calculated with a correction for the small (but linear) increase in catholyte volume with charge c passed due to water migration through the cation-ex¬ change membrane.

At Q _t = 100 percent, the conversion is 83 per¬ cent, CE = 85 percent, and the yield 85 percent. At Q _t = 125 percent, the corresponding values are conversion = 93 percent, CE = 71 percent and yield = 89 percent.

Example 1 b :

Example 1a was duplicated with the exception that the temperature was held constant at 5°C.

Example 1c:

Example 1a was duplicated with the exception that the temperature was held constant at 60°C.

Example Id:

Example 1a was duplicated with the exception that potassium hydroxide (5N) was utilized as anolyte and 1N KOH as the solvent for the catholyte.

Example let

Example 1d was duplicated with the exception that the catholyte solvent was 1M of K2CO3.

Example Ifi

Example la was duplicated with the exception that sodium carbonate (1M) was used as the catholyte electrolyte. The initial pH was 9.5 and the final pH was 13.7.

Example gt

Example 1a was repeated with the exception that sodium bicarbonate (1M) was the electrolyte in the

catholyte. The initial pH was 7.9 and the final pH was 13.6.

Example 1h:

Example 1a was again repeated with the exception that potassium dihydrogen phosphate/t-butanol solution (15 percent by volume) was used as cosolvent as the catholyte. A 0.33-ξ portion of solute was used in this example because of solubility limitations.

Example 1i:

Example 1a was duplicated with the exception that the current density was 150 mA/cm'p- ^* .

Example 1.j:

Example Λ a. was duplicated with the exception that an anion-exchange membrane (Raipore- ³ 5035 obtained from RAI Research Corp.) was used instead of the cation-exchange membrane. Some organic transferal through the membrane was noted by discoloration of the anolyte and membrane.

The results of the preceding examples are sum¬ marized in Table I.

TABLE I

V = 100% ^Q t ¹ = 125

% % % % % %

Example 1 Conv ² CE ³ Yield ⁴ Conv ² CE ³ Yield ⁴ a 83 85 85 93 71 89 b 78 71 72 88 62 78 c 91 88 86 - - - d 89 85 85 97 72 91 e 88 81 82 100 75 94 f 80 75 75 90 67 85 g 86 71 71 94 66 83 h 33 45 45 40 49 61 i 80 65 53 86 64 80 j 85 70 ,53 100 48 59

-Qt is as defined hereinbefore

-% Conv is percent of the nitro compound that is converted

³ % CE is current efficiency yield is mole percent of amine compound formed based on the nitro compound charged

As evidenced by the data of Table I, the pro¬ cess of this invention can be practiced using different current densities, different diaphragms/membranes, dif¬ ferent electrolytes and different temperatures. The best results, however, are obtained in this type of cell using current densities of 50 to 100 mA/cm ² , ambient temperatures and a cation-exchange membrane.

Example 2

The cathode material was varied to determine the effects of this parameter. All conditions were held constant as in Example 1a above except for the variance of cathode material. Except where noted, the cathode was of the same shape and dimension as the control experiment. The purity of metals was >99 percent except as noted. The area for calculation of current density was taken to be the area of one side of

10 the flag.

Run No. 2a: Copper

This experiment was the same as recorded in - m Example 1a above.

Run No. 2b:

Platinum was used as the cathode in this example. 0

Run No. 2c: Nickel

Expanded nickel was used as the cathode in this example.

5 Run No, 2d:

Lead was used as the cathode in this example.

Run No. 2e: 0 Tin was used as the cathode in this example

Run No. 2f: Stainless Steel

The cathode was a fine mesh of stainless steel (316 Alloy).

Run No . 2g t

Cobalt was used as the cathode in this example.

Run No. 2ht Silver was used as the cathode in this example.

Run No. 2it Graphite

The cathode was a cylinder of graphite. The area was estimated as the circumference times the length of the immersed portion of the rod.

The results of these examples are recorded in Table II.

TABLE II

^Q t ¹ = 100% ^Q t ¹ = 125%

% % % % % %

Run No. Cathode CD-s mA/cm ² Conv ² CE ³ Yield ⁴ Conv ² CE ³ Yield ⁴

2a Copper 79 83 85 85 93 71 89

2b Platinum 81 82 82 82 94 75 94

2c Nickel 84 90 84 85 *** ^* *

97 77 96

2d Lead 69 94 88 88 100 77 97

2e Tin 83 93 90 90 98 76 96

2f Stainless Steel 76 93 94 95 100 83 103

2g Cobalt 78 80 83 83 93 77 97

2h Silver 78 85 81 82 95 76 95

2i Graphite 106 79 78 78 89 70 88

'Qt is as defined in Table I

² % Conv is as defined in Table I

³ % CE is as defined in Table I % yield is as defined in Table I

⁵ CD is current density in millia ps/square centimeter

As evidenced by the data of Table II, the pro¬ cess of invention is effectively practiced using all of the listed materials as the cathode. However, lead and tin do exhibit a greater degree of corrosion than does copper.

Example 3

Cell Designt

The electrochemical cell used in this example was a parallel-plate, two-chamber design and was machined out of polypropylene. A copper cathode and a nickel anode (both 30 inches x 5 inches (76 cm x 15 cm)) were separated by a cation-exchange membrane which was physically supported by titanium screens on each side. Flow distribution was accomplished via 1/8-inch (0.3 cm) holes on 1/4-inch (0.6 cm) centers on top and bottom of each chamber.

Electrolysis:

The general procedure for electrolysis was to fill the anolyte reservoir with 5 liters of 5N NaOH which was supplemented with additional base when neces¬ sary in order to prevent pitting of the anode. The catholyte was then placed in the 12-liter reservoir and circulated via a centrifugal-type pump through the cell. In the reservoir was a reaction mixture contain¬ ing 104 g/liter of 3-nitro-4-hydroxybenzoic acid, 40 g/liter of sodium chloride and 80 g/liter of sodium hydroxide. A nitrogen sparge was kept over the catho¬ lyte at all times during the electrolysis. A small trickle current (approx. 25 mA) was kept flowing through the cell before and between runs to protect the copper from corrosion. After circulation of the

anolyte and catholyte were started (typically 600 and 1500 ml/min, respectively), the main rectifier was connected and 100 amps was passed through the cell. Aliquots of the catholyte were taken at intervals and analyzed via liquid chromatography. The current was adjusted stepwise to minimize the amount of hydrogen evolution at the cathode. The average current density was about 80 mA/cm ² and the temperature was ambient temperature.

Product isolation was via acidification of the catholyte. This was accomplished via aspiration of aliquots of the catholyte into side-arm flasks which contain con-HCl and typically 10 g/liter of SnCl ₂ (as antioxidant) . Table III indicates some of the results obtained with this cell.

TABLE III

Liquid Chromatogi r-aphic Results

Catho¬

Sample lyte vol mole Avg I % Isol % LC No. (liters) nitro' (A) ² % Conv ³ % Yield ⁴ % C ⁵ Yields Purity ⁷

1 7.32 3.969 73.0 96.9 96.5 91.0 90.4 99.90

2 8.00 4.312 71.2 98.8 98.6 89.8 88.5 99.97 l

3 9.00 4.914 72.3 >95 >98 - 87.9 100.00

4 6.00 3.226 75.0 98.9 94.5 85.8 89.6 99.95

5 6.13 3.327 73.6 98.4 93.4 84.8 90.2 99.89

'mole nitro represents the moles of 3-nitro-4-hydroxybenzoic acid charged

-Avg I (A) represents the average current (AMPS) during the batch electrolysis ^■ ''% Conv is as defined in Table I

'% Yield is as defined in Table I

*% CE is as defined in Table I

°% Isol Yield is the isolated yield of the desired product

'% LC Purity is the purity of isolated amine hydrochloride as measured by liquid chromatography

one-inch (2.5 cm) thick plexiglas tops and drilled for various fittings. The catholyte-reservoir top was

reservoirs. Stainless steel (■•-in. (0.6 cm)) tubing was coiled in each reservoir and supplied with cold water for cooling. Nitrogen purging or padding minimized the formation of carbonate and prevented air oxidation of the amine.

The power supply for the cell consisted of a rectifier capable of 18 volts (DC) and 2000 Amps (A). Five 00-welding cables provided adequate conduction to the cell to cause only slight voltage drop. A small power supply provided 0.25 A through the cell for cathodic protection whenever the main rectifier was shut off.

Syntheses

The general procedure for the batch electroly¬ sis was to fill the anolyte reservoir to approximately 50 liters of 5N NaOH. The catholyte consisting of 3-nitro-4-hydroxybenzoic acid (8-10 percent) in nomi¬ nally 2N NaOH was pumped Into a polyethylene reservoir, weighed and then transferred via slight N2 pressure into the catholyte reservoir. The pumps were started and current applied quickly thereafter. Initial cur¬ rents were varied from 600 to 1250 amps. Samples for liquid chromatographic analyses were taken at about every 20 percent of the theoretical charge. The ano¬ lyte was returned to original pH level after each batch electrolysis by addition of 50 percent NaOH. The cur¬ rent was controlled manually to minimize the amount of evolved hydrogen and to keep the cell voltage at or below 3V. Electrolysis was generally terminated at 115 to 125 percent of the theoretical charge (determined by a conversion greater than 97 percent). A final liquid chromatographic analysis, mass and density were

obtained to give the final conversion, yield and current efficiency.

Table IV shows the data and results for ten electrolyses. Isolated recrystallized yields are greater than 80 percent with greater than 99.9 percent purity. Cathode and anode corrosion are minimal. A high purity monomer is obtained in high yields in multi-Kg quantities with a power consumption significantly less than 2 kilowatt hour/lb.

TABLE IV Electrolyses Results (Chromatographic)

Run mole CD ³ . % % % % No. Nitro ¹ mk/Cvar Conv ² Yield ² CE ² 2 ²

1 19.2 77 98 99 86 115

2 22.2 103 98 97 84 116

3 21.2 121 98 96 83 115

4 22.2 134 98 100 84 120

5 20.0 131 97 100 83 121

6 24.0 137 98 91 79 115

7 20.5 133 97 96 81 120

8 21.5 134 98 99 82 121

9 20.0 133 98 103 82 126

10 20.7 137 98 101 84 120

-Moles of 3-nitro-4-hydroxybenzoic acid ² Same as defined in Table I ³ Same as defined in Table II

Example 5

Several classes of nitro aromatic compounds were subjected to cathodic reduction in basic media at a copper electrode.

^" le reactions were followed by liquid chroma- tography with a Hewlett Packard 1090A system which incorporated a diode array as the detector. Identifi¬ cation of the corresponding aniline products was accom¬ plished via retention time match and spectral authenti¬ cation. Quantitation of each product was via response

factor for authentic amine, either purchased with known purity, or synthesized in-house by nonelectrochemical methods.

Reaction conditions were identical to those in Example 2a unless stated differently. The major dif¬ ferences were changes in the solvent (usually addition of methanol) or temperature to increase the solubility of the nitro aromatic compound in the catholyte.

The reactants and products are recorded in Table V. This example demonstrates that at least six classes of nitro aromatic compounds provide good to excellent yields of amines in basic media.

TABLE V

Q _t ³ = 100% Q _t ³ = 125%

Run No. Reactant ¹ Product ²

% % % % Yield Conv Yield Conv

A NHBA(3,4) AHBA(3,4) 85 83 89 93

B NHBA ⁽ 4,3 ⁾ AHBA(4,3) 88 92 96 100

C NHBA(5,2) AHBA(5,2) 83 89 89 96

D NP(2) AP(2) 81 86 97 97

E NP(4) AP(4) 93 95 ND ⁴

F NP(3) AP(3) 44 81 ND ⁴ 92

G* NBA(2) ABA(2) 24 72

H* NBA(4) ABA(4) 23 100

I* NBA(3) ABA(3) 0 100

J NA(2) A(2) 41 85 52 94

K NA(4) A(4) 63 88 70 93

L NA(3) A ⁽ 3) 18 100 22 100

M MNP(4,2) MAP(4,2) 73 88 92 95

N MNP(3,2) MAP(3,2) 36 98 42 100

0 MNP(3,4) MAP(3,4) 93 94 100 100

P MNP(5,2) MAP(5,2) 103** 95 111** 100

Q MNP(3,2) MAP(3,2) 85 89 101 100

R NPT(4) PT(4) 60 >90 68 100

S* NB A 25 90 28 92

T* CNB(1,2) CA(1,2) 49 95 48 100 u* CNB(1,4) CA(1,4) 30 91 33 100

V NT(4) T(4) 55 100 w* NBSA(4) ABSA(4) 14 99 13 100

*Not an example of the invention

**Accuracy of the analytical results is poorer than normal ±5% for other runs

Run A is 3-nitro-4-hydroxybenzoic acid Run B is 3-hydroxy-4-nitrobenzoic acid Run C is 2-hydroxy-5-nitrobenzoic acid Run D is 2-nitrophenol Run E is 4-nitrophenol Run F is 3-nitrophenol Run G is 2-nitrobenzoic acid Run H is 4-nitrobenzoic acid Run I is 3-nitrobenzoic acid Run J is 2-nitroanisole Run K is 4-nitroanisole Run L is 3-nitroanisole Run M is 4-methyl-2-nitrophenol Run N is 3-methyl-2-nitrophenol Run 0 is 3-πιethyl-4-nitrophenol

10 Run P is 5-methyl-2-nitrophenol Run Q is 3-methyl-2-nitrophenol Run-R is 4-nitrophenetole Run S is nitrobenzene Run T is 1-chloro-2-nitrobenzene Run U is 1-chloro-4-nitrobenzene Run V is 4-nitrotoluene • _j t- Run W is p-nitrobenzenesulfonic acid

2 Run A is 3-amino-4-hydroxybenzoic acid

Run B is 3-hydroxy-4-aminobenzoic acid

Run C is 5-amino salicylic acid

Run D is 2-aminophenol

Run E is 4-aminophenol

Run F is 3-aminophenol 0 Run G is anthranilic acid

Run H is 4-aminobenzoic acid

Run I is 3-aminobenzoic acid

Run J is o-anisidine

Run K is p-anisidine

Run L is m-anisidine

Run M is 2-amino-p-cresol 5 Run N is 3-amino-o-cresol

Run 0 is 4-amino-m-cresol

Run P is 6-amino-m-cresol

Run Q is 3-methyl-2-aminophenol

Run R is p-phenetidine

Run S is aniline

Run T is 2-chloroaniline 0 Run -U is 4-chloroaniline

Run V is p-toluidine

Run W is p-aminobenzenesulfonic acid

Q _t is defined in Table I Not determined