反应详情

U.S. Pat. No. 2,417,897 and its corresponding U.S. Pat. No. Re. 23,024, which issued Mar. 25, 1947 and Aug. 17, 1948, respectively, disclose a three-step process for the preparation of 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, Crystal Violet Lactone (CVL). In the first step, 3-dimethylaminobenzoic acid is prepared from 3-aminobenzoic acid by alkylating the free amine using methyl iodide in the presence of potassium hydroxide. In the second step, the 3-dimethylaminobenzoic acid is condensed with 4,4'-bis(dimethylamino)benzhydrol in the presence of sulfuric acid to obtain 2-[bis(4-dimethylaminophenyl)methyl]-5-dimethylaminobenzoic acid. In the third step, the 2-[bis(4-dimethylaminophenyl)methyl]-5-dimethylaminobenzoic acid is oxidized using lead dioxide in dilute hydrochloric acid to obtain the CVL.