PROCESSES FOR THE SYNTHESIS OF SULFENTRAZONE

Abstract

Disclosed are processes for the synthesis of sulfentrazone, which provide a high conversion of sulfentrazone amine and high yield of the final sulfentrazone product.

Claims

1. A process for the synthesis of sulfentrazone, comprising reacting sulfentrazone amine of formula (i) with methanesulfonyl chloride ##STR00008## in the presence of a catalyst selected from imidazole, 1H-1,2,4-triazole, benzimidazole, a compound of Formula-A, a compound of Formula-B or salts thereof ##STR00009## wherein R in both Formulae-A and B each independently represents hydrogen, amino, optionally substituted C.sub.1-10 alkyl, C.sub.1-10 haloalkyl, C.sub.1-10 alkoxy or aryl.

2. The process of claim 1, wherein the compound of Formula-A is 2-methylimidazole, 4-methylimidazole, 5-methylimidazole, 2-ethylimidazole, 4-ethylimidazole, 5-ethylimidazole, 2-phenylimidazole, 4-phenylimidazole or 5-phenylimidazole.

3. The process of claim 1, wherein the compound of Formula-B is formamidine, acetamidine or salts thereof.

4. The process of claim 3, wherein the compound of Formula-B is formamidine hydrochloride, acetamidine hydrochloride, formamidine sulfate, acetamidine sulfate, formamidine phosphate or acetamidine phosphate.

5. The process of claim 1, wherein the process is carried out in a solvent.

6. The process of claim 2, wherein the solvent is selected from aromatic, alkane, and alkene solvents, and any mixtures thereof.

7. The process of claim 3, wherein the solvent is selected from toluene, xylene, diethylbenzene, and any mixtures thereof.

8. The process of claim 4, wherein the solvent is toluene.

9. The process of claim 1, wherein the process is carried out at an elevated temperature, with the preferred temperature ranging from about 110 C. to about 160 C.

10. The process of claim 6, wherein the temperature ranges from about 120 C. to about 130 C.

11. The process of claim 1, wherein the process is carried out at atmospheric pressure or higher pressure.

12. The process of claim 1, wherein the process is carried out at a pressure ranging from about 0.15 MPa to about 1 MPa.

13. The process of claim 1, wherein the catalyst is present in an amount ranging from about 0.01 to about 0.2 molar equivalents of sulfentrazone amine

14. The process of claim 13, wherein the catalyst is imidazole.

15. The process of claim 13, wherein the catalyst is present in an amount ranging from about 0.05 to 0.15 molar equivalent of sulfentrazone amine

16. The process of claim 15, wherein the catalyst is imidazole.

17. The process of claim 13, wherein the catalyst is benzimidazole, 2-methylimidazole, 2-ethylimidiazole, 2-phenylimidazole, formamidine hydrochloride or acetamidine hydrochloride and the catalyst is present in an amount ranging from about 0.01 to about 0.035 molar equivalents to sulfentrazone amine.

18. The process of claim 1, wherein methanesulfonyl chloride is present in excess of sulfentrazone amine.

19. The process of claim 18, wherein methanesulfonyl chloride is maintained in excess of sulfentrazone amine throughout the process.

20. The process of claim 18, wherein methanesulfonyl chloride and sulfentrazone amine are present in a molar ratio ranging from about 1 to about 2.

21. The process of claim 20, wherein methanesulfonyl chloride and sulfentrazone amine are present in a molar ratio ranging from about 1.5 to about 2.

22. A process for the preparation of a sulfonamide of formula II: ##STR00010## comprising reacting at elevated temperature at least the following: (1) an aniline of formula I: ##STR00011## with (2) a sulfonating agent A of the formula R.sup.1SO.sub.2Z in the presence of (3) a catalytic amount of a catalyst; wherein: the catalyst is imidazole, 1H-1,2,4-triazole, benzimidazole, 2-methylimidazole, 2-ethylimidiazole, 2-phenylimidazole, formamidine hydrochloride or acetamidine hydrochloride; X and Y in both formulae I and II and Z are each independently selected from the group consisting of hydrogen, halo, alkyl, haloalkyl, amino, nitro, alkoxy, hydroxy, anhydridyl, alkylthio, arylthiol, aryloxy, alkylsulfonyl, arylsulfonyl, and substituted or unsubstituted aryl, the substituents of said substituted aryl comprising one or more members selected from the group consisting of halo, C.sub.1-20 alkyl, C.sub.1-20 alkoxy, nitro, amino, amido, alkylthio, aryl, arylthio, aryloxy, alkylsulfonyl, and arylsulfony; R in both formulae I and II is selected from the group consisting of hydrogen, alkyl, haloalkyl, aryloxy, substituted or unsubstituted aryl and substituted or unsubstituted heterocyclyl, the substituents of said substituted aryl or heterocyclyl comprising one or more members selected from the group consisting of halo, C.sub.1-20 alkyl, C.sub.1-20 alkoxy, nitro, amino, amido, alkylthio, aryl, arylthio, aryloxy, alkylsulfonyl, and arylsulfonyl; and R.sup.1 is selected from the group consisting of hydrogen, alkyl, haloalkyl, and aryl.

23. The process of claim 22, wherein the catalyst is imidazole.

Description

EXAMPLES

Example 1

Synthesis of Sulfentrazone Using Sulfentrazone Amine as Starting Material

[0056] 80.3g of solid sulfentrazone amine (hereinafter SFTS-NH.sub.2), and 36.0g of toluene were charged into a 1-liter round-bottomed reaction flask equipped with bottom take-off stopcock. The reaction flask was fitted with a mechanical stirrer, reflux condenser, a thermocouple and a heating mantle Effluent gas was directed to a caustic scrubber containing 10% NaOH. Except as otherwise indicated all reactions of the Examples were carried out at normal atmospheric pressure.

[0057] The obtained SFTS-NH.sub.2 in toluene reaction medium was maintained at about 120-130 C., and 40.1 g of methanesulfonyl chloride was slowly charged to the reaction flask. Subsequently, 1.09g of imidazole (equaling 7% molar equivalent of SFTS-NH.sub.2) was added to the medium. The reaction temperature was maintained at about 120-130 C. throughout the reaction.

[0058] The reaction was held with agitation under reflux conditions at the temperature of about 120-130 C. until the conversion of SFTS-NH.sub.2 was greater than 99% by GC analysis (i.e., less than 1% unconverted SFTS-NH.sub.2 remains in the reaction medium).

[0059] When the reaction was completed, the mixture was cooled slowly to 80 C. and diluted using toluene (400g) to provide a 15 wt % sulfentrazone solution. This diluted mixture was quenched with water, followed by phase separation to collect the organic phase. The organic phase was further subject to crystallization and filtration and the crystals collected were then dried to give 86.5g of solid final product. As analyzed, the weight (percentage) assay was 92%, the isolated solid yield was 89.8%, and the yield in mother liquor (ML) was 5.9%. The overall yield of the final sulfentrazone was calculated to be 95.7%.

Example 2

Synthesis of Sulfentrazone Using Imidazole

[0060] The procedure of Example 1 to synthesize sulfentrazone was repeated except for varying the imidazole amount and reaction Time as set forth in the following Table 1, while keeping the remaining conditions unchanged. The results were summarized as follows. The total yield of sulfentrazone (SFT) was calculated as the sum of the Yield/Solid and Yield/ML. Imidazole residue remaining in the dried solid product was indicated as Imidazole (ppm) and the symbol / represents Not Measured.

TABLE-US-00001 TABLE 1 Imidazole Imidazole* Time Yield/ Yield/ Unreacted Yield/ Run (g) (ppm) (Hrs) Solid ML SFT5-NH2 SFT 1 0.545 g 8 4 88.17% 3.48% 0.90% 91.65% 2 0.545 g <1 4 90.16% 3.25% 0.89% 93.41% 3 0.545 g 21 4 90.69% 3.04% 0.83% 93.73% 4 0.545 g / 9 88.94% 4.61% 0.78% 93.55% 5 0.545 g / 8 89.82% 3.70% 0.93% 93.52% 6 0.545 g / 12 91.20% 4.28% 0.85% 95.48% 7 1.09 g 19 5 90.93% 3.11% 0.51% 94.04% 8 1.09 g 14 6 91.34% 3.28% 0.45% 94.62% 9 1.09 g 10 12 88.18% 5.70% 1.36% 93.88% 10 1.09 g 9 10 90.75% 5.61% 0.98% 96.36% 11 1.09 g 15 8 91.80% 4.53% 1.03% 96.33% 12 1.09 g 7 8 90.73% 5.55% 0.76% 96.28% 13 1.09 g 16 8 89.89% 5.89% 0.71% 95.78% *represents the imidazole residual in the obtained sulfentrazone product

Comparative Example 3

Synthesis of Sulfentrazone Using Dimethylformamide (DMF) as Catalyst

[0061] The same procedures of Example 1 were repeated except for replacing imidazole with DMF and varying the reaction Time as indicated in the following Table 2. The results were summarized as follows. 0.585g DMF, equaling to 3.5% of SFT-NH.sub.2 by molar equivalence was used in all comparison examples.

TABLE-US-00002 TABLE 2 Unreacted DMF Time/ Yield/ Yield/ SFT-NH.sub.2 Yield/ Comp. (g) (Hrs) Solid ML (wt %) SFT 1 0.585 g 6 85.94% 5.00% 1.92% 90.94% 2 0.585 g 5 87.16% 5.55% 1.10% 92.71% 3 0.585 g 4 88.47% 4.65% 1.57% 93.12% 4 0.585 g 5 87.89% 3.37% 1.60% 91.26%

[0062] As shown in the results of Examples 1 and 2, the present processes using imidazole as catalyst provide a high sulfentrazone amine conversion (99% or even higher), as well as higher sulfentrazone yield (e.g., 94%, 95%, 96% or even higher). In comparison with the DMF process as demonstrated in Example 3, the conversion rate and the sulfentrazone yield are both improved.

[0063] These improvements are significant from the perspective of industrial-scale manufacture and bring significant cost reduction. Further, unlike the DMF process where DMF can partially react with sulfentrazone amine, thereby leading to the formation of undesired byproducts and in turn lowering the sulfentrazone yield, imidazole does not react with sulfentrazone amine and therefore unwanted byproducts are avoided.

[0064] Another advantage of the present process is that imidazole has a high solubility in water, and thus most of the imidazole is dissolved in the waste water and taken away from the final sulfentrazone product. As shown in Table 1, the residual imidazole in the sulfentrazone solid is less than 25 ppm. That not only simplifies the purification treatment, but also improves the purity of the final sulfentrazone product by reducing byproducts found in the DMF process.

Example 4

Synthesis of Sulfentrazone by Varying Catalyst

[0065] Repeat the procedure of Example 1 by using different catalysts in replace of imidazole. The following Table 3 outlines the reagents and catalysts used in the present example, and reaction times as well as the conversion rate of from SFT 5-NH.sub.2 to the desired sulfentrazone.

TABLE-US-00003 TABLE 3 Reaction Conversion Amount Time Rate (by (g) Mole (Hrs) HPLC) Reagent/ SFT 5-NH.sub.2 31 0.10 / / Solvent Toluene 10 0.11 / / Methanesulfonyl 17.5 0.15 / / chloride Catalyst Benzimidazole 0.4 0.0035 3 96.9% 2-Methylimidazole 0.3 0.0035 3 98.0% 2-Ethylimidazole 0.3 0.0035 3 98.9% 2-Phenylimidazole 0.4 0.0035 3 96.8% Formamidine 0.3 0.0035 3 92.9% hydrochloride Acetamidine 0.3 0.0035 3 98.2% hydrochloride
As showed in Table 3, the catalysts of the present invention all provide a high conversion of from SFT 5-NH.sub.2 to the final sulfentrazone product.