WST-8 CAS 193149-74-5

Take compound 2 (4.94 g, 0.0322 mol) into a 500 ml three-necked flask, add 150 ml of methanol, heat and stir until reflux to dissolve. After cooling to 50°C, compound 1 (10.0 g, 0.0322 mol) was added slowly. The constant temperature was 50°C, and stirring was continued for 2h. Filtration under reduced pressure and washing with a small amount of methanol gave compound 3 (11.065 g, 0.0249 mol) with a yield of 77.4%.

1H-NMR (400MHz, D2O) δH: 6.83 (d, 2H, J=9Hz), 7.65 (dd, 1H, J=8Hz, 1Hz), 7.81 (d, 2H, J=9Hz), 7.93 (d, 1H) , J=8Hz), 8.03 (d, 1H, J=1Hz), 8.31 (s, 1H).

Take 2-methoxy-4-nitroaniline (3.7g, 0.0220mol) in a 50ml single-neck flask, ice bath at -10~0°C, and add 15ml of hydrochloric acid solution diluted with 6.67ml of concentrated hydrochloric acid with water. Stir for 5 minutes. Then a solution of sodium nitrite (1.64 g, 0.0237 mol) dissolved in 10 ml of water was slowly added dropwise. After the addition was completed, stirring was continued for 30 min. That is, the diazonium salt solution is obtained. Standby (out of the box).

Take compound 3 (10.0 g, 0.0224 mol) in a 500 ml three-neck flask, add 200 ml methanol, and stir for 5 min. Then, the above-mentioned diazonium salt solution was added thereto while adding 15 ml of an aqueous solution of NaOH (3.6 g, 0.09 mol). After the addition was completed, the mixture was stirred in an ice bath at -10~5°C for 2 hours and at room temperature for 2 hours. At this time, the reaction system was dark green. Use 4ml of concentrated hydrochloric acid to dilute 8ml of hydrochloric acid solution with water to dark red. The solvent was evaporated to dryness. 200 ml of petroleum ether was added to sonicate, and the mixture was filtered under reduced pressure to obtain compound 4 (12.054 g, 0.0193 mol) as a reddish-brown solid with a yield of 86.2%.

1H-NMR (400MHz, D2O) δH: 3.65 (s, 3H), 7.42 (t, 4H), 7.50 (d, 1H, J=2Hz), 7.69 (d, 1H, J=9Hz), 8.03 (m, 3H), 8.33 (d, 1H, J=1Hz).

Take compound 4 (12.054g, 0.0193mol) in a 500ml single-neck bottle, add 120ml methanol, and it turns dark reddish brown. Stir for 5 minutes. 100 ml of NBS (5.0 g, 0.0281 mol) in acetone was added. After stirring for about 1 h, the color became lighter, and the stirring was continued until the reaction system turned yellow. Filtration under reduced pressure gave a yellow-green solid. Recrystallization (ethanol/water=2), vacuum drying to obtain compound 2-(2-methoxy-4-nitrobenzene)-3-(4-nitrobenzene)-5-(2,4-disulfonic acid) phenyl)-2H-tetrazolium monosodium salt (6.211 g, 0.0099 mol), pale yellow solid powder, yield 51.6%.

1H-NMR(400MHz, D2O)δH: 3.54(s, 3H), 7.95(m, 6H), 8.13(d, 1H, J=8Hz), 8.34(m, 3H); 1H-NMR(400MHz, d6- DMSO)δH: 3.74(s, 3H), 7.86(m, 2H), 8.06(d, 1H, J=2Hz), 8.14(d, 2H, J=9Hz), 8.24(dd, 1H, J=8Hz, 2Hz), 8.30 (d, 1H, J=1Hz), 8.54 (d, 3H, J=9Hz).