# US 5,710,343 A · Method for the preparation of 3,4-dihydroxy-5-nitrobenzaldehyde

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- Number: US 5,710,343 A
- Document ID: US5710343A
- Status: Granted
- Kind: A
- Application number: 08/809,405
- Filed: 1997-05-08
- Granted: 1998-01-20
- Earliest claimed: 1994-09-23
- Assignees: Orion-yhtyma Oy
- Inventors: Reijo Johannes Backstrom
- Web page: https://patentgrep.com/patent/US5710343A

## CPC

- C07C 201/12: by reactions not involving the formation of nitro groups
- C07C 201/16: Separation; Purification; Stabilisation; Use of additives
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

The invention provides a method for the preparation of 3,4-dihydroxy-5-nitrobenzaldehyde by reacting 3-ethoxy-4-hydroxy-5-nitrobenzaldehyde with a reagent comprising zinc chloride, water and hydrogen chloride.

## Claims

### Claim 1

A method for the preparation of 3,4-dihydroxy-5-nitrobenzaldehyde characterized in that 3-ethoxy-4-hydroxy-5-nitrobenzaldehyde is reacted with a reagent comprising zinc chloride, water and hydrogen chloride.

### Claim 2 (depends on 1)

The method according to claim 1, characterized in that the amount of zinc chloride is from 1.5 kg to 25 kg per 1 kg of 3-ethoxy-4-hydroxy-5-nitrobenzaldehyde.

### Claim 3 (depends on 2)

The method according to claim 2, characterized in that the amount of zinc chloride is from 2.5 kg to 4 kg per 1 kg of 3-ethoxy-4-hydroxy-5-nitrobenzaldehyde.

### Claim 4 (depends on 1)

The method according to claim 1, characterized in that the amount of the hydrochloric acid is from 0.17L to 0.6L per 1 kg of zinc chloride.

### Claim 5 (depends on 4)

The method according to claim 4, characterized in that the amount of the hydrochloric acid is from 0.22L to 0.4L per 1 kg of zinc chloride.

### Claim 6 (depends on 1)

The method according to claim 1, characterized in that the concentration of the hydrochloric acid is from 10% to 40%.

### Claim 7 (depends on 6)

The method according to claim 6, characterized in that the concentration of the hydrochloric acid is from 20% to 38%.

### Claim 8 (depends on 1)

The method according to claim 1, characterized in that the temperature is from 70.degree. C. to 130.degree. C.

### Claim 9 (depends on 8)

The method according to claim 8, characterized in that the temperature is from 80.degree. C. to 110.degree. C.

### Claim 10 (depends on 1)

The method according to claim 1, characterized in that the crude product is further crystallized from toluene.