p-Toluenesulfonic acid → 2-(4'-Chloromethylphenyl)-7-chlorobenzoxazole

Participants

Reaction Steps

158.5 g of 2-(4'-chloromethylphenyl)-7-chlorobenzoxazole (produced by condensation of 2-amino-6-chlorophenol with 4-chloromethyl-benzoyl chloride and subsequent cyclisation in o-dichlorobenzene in the presence of p-toluenesulfonic acid, melting point 141° to 142° C.) is heated with 400 ml of triethyl phosphite in the course of 2 hours at 155° C., and the mixture is subsequently stirred at 155° to 158° C. for a further 7 hours. After cooling to 90° C., the unreacted triethyl phosphite is distilled off in vacuo. The reaction product, which is still oily, is stirred into 1000 ml of petroleum ether, and after a short time crystallisation occurs. The product is filtered off, washed with petroleum ether and dried. The yield is 210 g (97% of theory) of 2-(4'-diethylphosphonomethylphenyl)-7-chlorobenzoxazole having a melting point of 92° to 93° C.

Provenance & Evidence