3H-Indazol-3-one, 1,2-dihydro-1-(phenylmethyl)-, sodium salt (1:1)

4) Take 300g of the BZ-02 obtained above into a 3L three-necked flask, add 1200g of water and magnetically stir, and then slowly add 357g of NaOH solution with a mass fraction of 30percent, and the reaction system is suspended; The oil bath was warmed to an internal temperature of 80-85° C. and fully reacted. After the solution became clear, 25 g of activated carbon was added and stirred for 30 min. After hot filtration, the filtrate was slowly cooled after filtration, and the ice bath was stirred for 1 hour and then filtered again. The filter cake was beaten with 600 mL of toluene and 600 mL of ethyl acetate for 10 minutes to obtain an off-white solid 326.0 g of BZ-03. 120 g of a white solid was dehydrated with xylene at a temperature of 140° C. to obtain 45 mL of water and 75 g of 1-benzyl-3-hydroxy-1H-3-carbazole sodium salt. In the conversion step 4), a total of 203.75 g of 1-benzyl-3-hydroxy-1H-3-carbazole sodium salt was obtained. According to the method for preparing the 1-benzyl-3-hydroxy-1H-3-carbazole sodium salt of the present invention, the final product has a purity of 97.94percent and a yield of 62.4percent.