# US 5,705,666 A · Process for the preparation of crystalline O-isopropylisourea hydrochloride

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- Number: US 5,705,666 A
- Document ID: US5705666A
- Status: Granted
- Kind: A
- Application number: 08/665,421
- Filed: 1996-06-19
- Granted: 1998-01-06
- Earliest claimed: 1995-06-27
- Assignees: SKW Trostberg Aktiengesellschaft
- Inventors: Stefan Weiss
- Web page: https://patentgrep.com/patent/US5705666A

## CPC

- C07C 273/1836: {from derivatives of carbamic acid}
- C07C 273/1809: {with formation of the N-C(O)-N moiety}
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

Disclosed is a process for the preparation of crystalline O-isopropylisourea hydrochloride, wherein cyanamide, chloroformamidinium chloride and isopropanol are reacted, an aprotic solvent preferably selected from the group consisting of ketones, ethers, esters and acetals, is added to the reaction mixture before, during and/or after the reaction and, optionally after cooling the reaction solution, the crystalline reaction product is separated off. O-isopropylisourea hydrochloride is obtained in a very pure and coarse crystalline form by the process of the invention.

## Claims

### Claim 1

A process for the preparation of crystalline O-isopropylisourea hydrochloride, comprising: (a) reacting cyanamide, chloroformamidinium chloride and isopropanol in a reaction mixture to form a crystalline reaction product; (b) adding an aprotic organic solvent to the reaction mixture before, during and/or after the reaction; and, (c) separating off the crystalline reaction product.

### Claim 2 (depends on 1)

The process of claim 1 wherein the reaction solution is cooled prior to step (c).

### Claim 3 (depends on 1)

The process of claim 1 wherein the reaction takes place at a temperature of from 0.degree. C. to 100.degree. C.

### Claim 4 (depends on 1)

The process of claim 1 wherein the aprotic organic solvent is selected from the group consisting of ketones, ethers, esters, and acetals.

### Claim 5 (depends on 1)

The process of claim 1 wherein the mole ratio of cyanamide to chloroformamidinium chloride is from 1:0.5 to 1:2.

### Claim 6 (depends on 1)

The process of claim 1 wherein 2 to 10 moles of isopropanol are used per mole of cyanamide.

### Claim 7 (depends on 1)

The process of claim 1 wherein 2.5 to 3.5 moles of isopropanol are used per mole of cyanamide.

### Claim 8 (depends on 1)

The process of claim 1 wherein the aprotic organic solvent is used in an amount of 50 to 1000 g per mole of cyanamide.

### Claim 9 (depends on 1)

The process of claim 1 wherein the organic solvent is used in an amount of 300 to 500 g per mole of cyanamide.

### Claim 10 (depends on 1)

The process of claim 1 wherein the aprotic organic solvent is acetone.

### Claim 11 (depends on 1)

The process of claim 1 wherein the aprotic organic solvent is isopropyl acetate.

### Claim 12 (depends on 1)

The process of claim 1 wherein the chloroformamidinium chloride is produced, without subsequent isolation, from hydrogen chloride and cyanamide in isopropanol, optionally in the presence of a further solvent.

### Claim 13 (depends on 1)

The process of claim 1 wherein a mixture of cyanamide and chloroformamidinium chloride is prepared in situ by the reaction of cyanamide and hydrogen chloride in isopropanol, optionally in the presence of a further solvent.

### Claim 14 (depends on 1)

The process of claim 1 wherein the reaction is carried out at a temperature of 30.degree. to 60.degree. C.

### Claim 15 (depends on 1)

The process of claim 1 wherein, after the reaction, the reaction mixture is cooled to a temperature of from 10 to 1.degree. C.

### Claim 16 (depends on 15)

The process of claim 15 wherein the reaction mixture is seeded by the addition of crystalline O-isopropylisourea hydrochloride.