Reacción #465955

Ecuación de reacción

NaOH

4-amino-3,5,6-trichloropyridine-2-carboxylic acid

→

4-Amino-3,6-dichloropyridine-2-carboxylic Acid

Disolventes

water

Condiciones de reacción

Tratamiento posterior

1. 1
   Filtraciónfiltered through a paper
2. 2
   Filtraciónfilter
3. 3
   Otroa temperature of 30° C.
4. 4
   Temperaturato maintain
5. 5
   Concentraciónthe NaOH concentration at a 1.5 to 2.0 percent excess
6. 6
   workup.WAITAfter about 15 hours (hr)
7. 7
   Otrothe electrolysis was terminated
8. 8
   Filtraciónthe cell effluent was filtered through a paper
9. 9
   Filtraciónfilter
10. 10
    Concentraciónconcentrated to about 750 g of crude
11. 11
    Concentraciónconcentrate
12. 12
    workup.STIRRINGwith stirring
13. 13
    Otroover 30 min
14. 14
    TemperaturaThe resulting slurry was cooled to ambient temperature
15. 15
    Filtraciónfiltered
16. 16
    LavadoThe filter cake was washed with 3×200 milliliter (mL) portions of water
17. 17
    Otrodried under vacuum at 80° C

Procedimiento

In a 3-liter (L) beaker was added 2000 grams (g) of hot water, 115.1 g of 50 percent by weight NaOH, and 200 g of wet 4-amino-3,5,6-trichloropyridine-2-carboxylic acid (79.4 percent). The solution was stirred for 30 minutes (min), filtered through a paper filter, and transferred to a 5-L feed/recirculation tank. This solution weighed 2315 g and contained 6.8 percent 4-amino-3,5,6-trichloropyridine-2-carboxylic acid. This feed was recirculated at a rate of about 9.46 L/min and a temperature of 30° C. through an undivided electrochemical cell having a Hastelloy C anode and an expanded silver mesh screen cathode. After normal anodization at +0.7 volt (v), the polarity of the cell was reversed and the electrolysis was started. The cathode working potential was controlled at −1.1 to −1.4 v relative to an Ag/AgCl (3.0 M Cl−) reference electrode. While recirculating the feed, a solution of 50 percent NaOH is slowly pumped into the recirculation tank to maintain the NaOH concentration at a 1.5 to 2.0 percent excess. After about 15 hours (hr), the electrolysis was terminated and the cell effluent was filtered through a paper filter. The solution was neutralized with concentrated HCl and concentrated to about 750 g of crude concentrate. The concentrate was warmed to 85° C. with stirring and the pH was adjusted to less than 1 with concentrated HCl over 30 min. The resulting slurry was cooled to ambient temperature and filtered. The filter cake was washed with 3×200 milliliter (mL) portions of water and dried under vacuum at 80° C. The dried product, 118.1 g assayed at 90.6 percent desired product; gas chromatography (GC) indicated about 4 percent 4-amino-3,5,6-trichloropyridine-2-carboxylic acid remaining as an impurity. A purified sample of 4-amino-3,6-dichloropyridine-2-carboxylic acid had a melting point (mp) of 185-187° C. (dec.); 1H NMR (DMSO-d6): δ 13.9 (br, 1H), 7.0 (br m, 2H), 6.8 (s,1H); 13C NMR {1H} (DMSO-d6): δ 165.4 (1C), 153.4 (1C), 149.5 (1C), 147.7 (1C), 111.0 (1C), 108.1 (1C).

Fuente