Thionyl Chloride → 5-Chlorocarbonylphthalide

Participants

Reaction Conditions

Reaction Steps

To a mixture of 1800 ml of thionyl chloride and 8.1 ml of N,N-dimethylformamide, 750 g (4.21 moles) of 5-carboxyphthalide are added under stirring. The mixture is heated slowly to reach an inner temperature of 60° C. in one hour, then it is kept at this temperature for another hour and finally it is brought to the reflux. After refluxing for 6 hours, about 600 ml of thionyl chloride are distilled off at a temperature of 80÷85° C., by replacing them by addition of toluene. Distillation is continued for a total of 2800 ml with concurrent replacement of the solvent by addition of 3800 ml of toluene. The mixture is slowly cooled and, at 80° C., the crystallization of the product begins. Cool to 10÷15° C. by continuing stirring for 15 hours. The hygroscopic product is filtered, washing with a total of 1500 ml of toluene, then it is dried under vacuum at 55° C. to give 710 g (86%) of 5-chlorocarbonylphthalide with a purity of 99% (HPLC).

Provenance & Evidence