# US RE34,745 E · High purity process for the preparation of 4,6-diamino-1,3-benzenediol

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- Number: US RE34,745 E
- Document ID: USRE34745E
- Status: Granted
- Kind: E
- Application number: 07/973,925
- Filed: 1992-11-09
- Granted: 1994-09-27
- Earliest claimed: 1986-10-30
- Assignees: The Dow Chemical Company
- Inventors: Zenon Lysenko
- Web page: https://patentgrep.com/patent/USRE34745E

## Abstract

High purity 4,6-dinitro-1,3-benzenediol is prepared by (a) contacting a 1,2,3-trihalobenzene with a nitrating agent and an acid under reaction conditions such that a 1,2,3-trihalo-4,6-dinitrobenzene is produced, (b) contacting the 1,2,3-trihalo-4,6-dinitrobenzene prepared in (a) with an alkanol and a base under reaction conditions such that as 4,6-dinitro-2-halo-1,3-benzendiol is produced, and (c) contacting the 4,6-dinitro-2-halo-1,3-benzenediol prepared in (b) with a hydrogenating agent in the presence of a solvent and a catalyst under reaction conditions such that a 4,6-diamino-1,3-benzendiol is produced. This 4,6-diamino-1,3-benzene diol is useful in the preparation of high molecular weight polybenzoxazoles.

## Claims

### Claim 1

A process for the preparation of 4,6-diamino-1,3-benzenediol in high purity comprising the steps of
(a) contacting a 1,2,3-trihalobenzene with a nitrating agent and an acid under reaction conditions such that a 12,3-trihalo-4,6-dinitrobenzene is produced:
(b) contacting the 1,2,3-trihalo-4,6-dinitrobenzene with an alkanol and a base under reaction conditions such that a 4,6-dinitro-2-halo-1,3-benzenediol is produced; and
(c) contacting the 4,5-dinitro-2-halo-1,3-benzenediol with a hydrogenating agent in the presence of a solvent and a catalyst under reaction conditions such that a 4,6-diamino-1,3-benzenediol is produced.

### Claim 2 (depends on 1)

The process of claim 1 wherein the 1,2,3-trihalobenzene is 1,2,3-trichlorobenzene.

### Claim 3 (depends on 2)

The process of claim 2 wherein the nitrating agent is nitric acid, the acid in step (a) is sulfuric acid, the alkanol is methanol, the base is sodium hydroxide, the hydrogenating agent is hydrogen and the catalyst is a palladium-on-carbon hydrogenation catalyst.

### Claim 4 (depends on 1)

The process of claim 1 wherein the 4,6-diamino-1,3-benzenediol is recovered in a purity of at least 99 weight percent.

### Claim 5 (depends on 1)

The process of claim 1 wherein the 4,6-diaminobenzenediol is recovered in a purity of at least 99.9 weight percent.

### Claim 6 (depends on 3)

The process of claim 3 wherein the molar ratio of concentrated nitric acid to the trichlorobenzene is in the range of about 2.1:1 to about 2.5:1, the molar ratio of sulfuric acid to the trichlorobenzene is in the range from about 11:1 to about 15:1 and the temperature in step (a) is in the range from about 15.degree. C. to about 80.degree. C.

### Claim 7 (depends on 6)

The process of claim 6 wherein the molar ratio of ethanol to the trichlorodinitrobenzene is in the range from about 1:1 to about 15:1 and the temperature in step (b) is in the range from about 25.degree. C. to about 85.degree. C.

### Claim 8 (depends on 7)

The process of claim 7 wherein the mole ratio of hydrogen gas to the 4,6-dinitro-2-chloro-1,3-benzenediol is in the range from about 7 to about 2000, the molar equivalent ratio of the hydrogenation catalyst to 4,6-dinitro-2-chloro-1,3-benzenediol is in the range from about 0.01:1 to about 0.5:1 and the temperature used in step (c) is from about 40.degree.0 C. to about 5020 C.

### Claim 9

A process comprising the step of contacting a 1,2,3-trihalo-4,6-dinitrobenzene with an alkanol and a base that can generate hydroxide ion under conditions such that a 4,6-dinitro-2-halo-1,3-benzenediol is formed.

### Claim 10 (depends on 9)

The process of claim 9 wherein the temperature of the reaction is between 0.degree. C. and 150.degree. C., inclusive.

### Claim 11 (depends on 10)

The process of claim 10 wherein the base is an alkali metal hydroxide, and the molar ratio of base to a 1,2,3-trihalo-4,6-dinitrobenzene is between 1:1 and 6:1, inclusive.

### Claim 12 (depends on 11)

The process of claim 11 wherein the alkanol is methanol, ethanol or propanol, and the molar ratio of alkanol to 1,2,3-trihalo-4,6-dinitrobenzene is between 1:1 and 15:1, inclusive.