Hydrochloric Acid → 2,7-Dichloro-9H-xanthene-9-carboxylic acid

Reaction equation

[CH:1]1[C:14]2[CH:13]([C:15]([OH:17])=[O:16])[C:12]3[C:7](=[CH:8][CH:9]=[CH:10][CH:11]=3)[O:6][C:5]=2[CH:4]=[CH:3][CH:2]=1.[Cl:18]N1C(=O)CCC1=O.[ClH:26]>C(O)(=O)C>[Cl:26][C:2]1[CH:3]=[CH:4][C:5]2[O:6][C:7]3[C:12](=[CH:11][C:10]([Cl:18])=[CH:9][CH:8]=3)[CH:13]([C:15]([OH:17])=[O:16])[C:14]=2[CH:1]=1

Participants

Procedure

To a suspension of 10 g of xanthene-9-carboxylic acid and 14 g of N-chlorosuccinimide in 80 mL of acetic acid was added with stirring dropwise 2.0 mL of conc. HCl over a period of 5 minutes. The mixture was stirred at room temperature for 12 hours and quenched by the addition of 150 mL of water. The precipitated solid was removed by filtration, rinsed with water, and dried in air to give 12.6 g (100%) of the crude carboxylic acid as a white solid. Recrystallization from MeOH--EtOAc (2:1) gave 6.98 g (55.2%) of the pure 2,7-dichloroxanthene-9-carboxylic acid as colorless small needles, m.p. 273°-275° C. (dec.); IR (KBr): 2970 (b, OH), 1695 (C=O) cm-1 ; 1H NMR (DMSO-d6): δ 5.01 s, 1H, CH), 7.05-7.50 (m, 6H, aryl).