Crystal violet lactone

1.Purpose
It is an important functional dye for producing pressure-sensitive materials.

2.Production method

Example 1: In a 500 mL three-necked flask, 21.5 g (purity 97.0%) of 2-[4,4′-diaminodiphenylmethyl]-5-dimethylamino benzoic acid was added, followed by the addition of 250 mL of deionized water. The resulting suspension was stirred and then 21.5 g of activated carbon (model: SHIRASAGI-C, produced by Takeda Chemical Industry Co., Ltd.) and 2.0 g of 49% NaOH aqueous solution were added. The reaction system was heated to 90-95°C and maintained within this temperature range. During the reaction, air was introduced into the reaction system at a rate of 400 mL/min for 9 hours. After the reaction was completed, the reaction mixture was filtered hotly, the filter cake was collected and re-dispersed with deionized water. 19.5 g of 36% HCl aqueous solution was slowly added to the dispersion liquid until the solid was completely dissolved. Then, the activated carbon was filtered out. The filtrate was adjusted to a pH of 7.0 with 49% NaOH aqueous solution to precipitate the target product crystals. The crystals were suction-filtered, washed with cold water, dried under vacuum, and 20.1 g of 3,3-bis(4-dimethylamino phenyl)-6-dimethylamino benzoic acid was obtained, with a yield of 95.4%. Analyzed by HPLC, the yield of by-products was 1.5% and the reaction selectivity was 98.4%.