Impact of trace elements in the Grignard reaction

Abstract

The present invention relates to an improved process for preparing 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine (DICAT) comprising reacting 4-bromoanisole with magnesium, and reacting the resulting Grignard reagent with cyanuric chloride, wherein the magnesium comprises additional metals as impurities in an amount of less than 0.027% by weight, based on the total weight of the magnesium.

Claims

1. A process for preparing a compound of formula I ##STR00010## comprising the steps of (i) reacting 4-bromoanisole with magnesium to obtain a Grignard reagent; and (ii) reacting the Grignard reagent obtained in step (i) with a compound of formula (II) ##STR00011## wherein the magnesium of step (i) comprises additional metals as impurities in an amount of less than 0.027% by weight, based on the total weight of the magnesium.

2. The process according to claim 1, wherein the magnesium comprises the additional metals in an amount of less than 0.02% by weight, based on the total weight of the magnesium.

3. The process according to claim 1, wherein the additional metals are selected from the group consisting of aluminum, manganese, silicon, iron, copper and calcium.

4. The process according to claim 1, wherein the magnesium comprises magnesium oxide in an amount of less than 0.35% by weight, based on the total weight of the pure magnesium.

5. The process according to claim 1, wherein the magnesium comprises metallic magnesium in an amount of more than 99.6% by weight, based on the total weight of the pure magnesium.

6. The process according to claim 1, wherein the magnesium is provided in the form of shavings, powder or flakes.

7. The process according to claim 1, wherein the compound of formula I is obtained in a yield of at least 95%.

8. The process according to claim 1, wherein the solvent of one or both of step (i) and step (ii) is an aprotic solvent.

9. The process according to claim 1, wherein the solvent is diethylether or tetrahydrofuran.

10. The process according to claim 1, wherein the reaction temperature of step (i) is in the range of from 35° C. to 80° C.

11. The process according to claim 1, wherein the reaction temperature of step (ii) is in the range of from 0° C. to 15° C.

12. The process according to claim 1, wherein in step (i) the 4-bromoanisole is added to the magnesium, wherein the magnesium is provided in a solvent according to claim 8, and in step (ii) the Grignard reagent obtained in step (i) is added to the compound of formula (II), wherein the compound of formula (II) is provided in a solvent according to claim 8.

13. The process according to claim 1, wherein in step (i) 4-bromoanisole and magnesium are reacted with each other in a molar ratio of from 1.2:1 to 1:1.2, or wherein in step (ii) the Grignard reagent obtained in step (i) is reacted with the compound of formula (II) in a molar ratio of from 1.2:1 to 1:1.2.

14. The process according to claim 1, wherein the process further comprises reacting the compound of formula (I) with resorcinol in the presence of AlCl.sub.3 to obtain a compound of formula (III) ##STR00012##

15. The process according to claim 14, wherein the process further comprises reacting the compound of formula (III) with isooctyl chloride in the presence of a base to obtain a compound of formula (IV) ##STR00013##

16. The process according to claim 8, wherein the solvent is selected from the group consisting of diethylether, tetrahydrofuran, trimethylamine and 1,4-dioxane.

17. The process according to claim 1, wherein in step (i) 4-bromoanisole and magnesium are reacted with each other in a molar ratio of from 1.2:1 to 1:1.2, and wherein in step (ii) the Grignard reagent obtained in step (i) is reacted with the compound of formula (II) in a molar ratio of from 1.2:1 to 1:1.2.

Description

EXAMPLES

Example 1

General Procedure for the Preparation of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine (DICAT)

(1) In a first reaction vessel, 1.0 mol magnesium was added to 2.5 mol tetrahydrofuran. The mixture was heated to 45° C. Then, 1.0 mol 4-bromoanisole was added at a temperature of about 70° C. The reaction mixture was allowed to cool to room temperature. In a second reaction vessel, 12.7 mol tetrahydrofuran was provided. 1.0 mol cyanuric chloride was added. At a temperature of about 7° C., the Grignard reagent obtained in the first reaction vessel was added to the mixture in the second reaction vessel. The reaction was completed after 2 hours. The solvent was removed.

(2) The following table provides the yields of DICAT, if magnesium is used, which comprises additional metals as impurities in an amount of less than 0.027% by weight, based on the total weight of the magnesium:

(3) TABLE-US-00001 Magnesium Met. Mg Al Mn Si Fe Cu Ca Mg MgO Yield No. [%] [%] [%] [%] [%] [%] [%] [%] [%] [%] 1 99.7 0.0048 0.0038 0.0047 0.0029 0.0004 0.0003 99.98 0.12 96 2 99.7 0.0043 0.0072 0.0028 0.0025 0.0004 0.0001 99.98 0.05 94.6 3 99.7 0.0011 0.0039 0.0043 0.0024 0.0001 0.0016 99.99 0.05 95.2