Hydrochloric Acid → 4-(2,3-Dimethoxybenzoyl)piperidine

Participants

Reaction Conditions

Reaction Steps

To the reaction solution of 4-(2,3-dimethoxybenzoyl)-1-piperidinecarboxylic acid, 1,1-dimethylethyl ester (7) from Example 76, Scheme G, step c, is added about 188 kg of water and 37% hydrochloric acid (39 kg, 395 mol). The solution is heated to about 60° C. for about 18 hours1. The mixture is cooled to about 25° C. and about 47 kg of toluene is added. The phases are separated and the organic phase is discarded. To the aqueous phase is added about 78 kg water, 50 wt % sodium hydroxide solution (31 kg, 391 mol), and about 99 kg of toluene. The phases are separated and the aqueous phase is discarded. The organic phase is concentrated by vacuum distillation. The concentration of 4-(2,3-dimethoxybenzoyl)piperidine (16) in solution ranges from 17 to 53 wt %1, affording 14.6 to 17.9 kg of 4-(2,3-dimethoxybenzoyl)piperidine (16) (65-76% yield). 1The solution is sampled and analyzed by HPLC assay to confirm complete deprotection to afford 4-(2,3-dimethoxybenzoyl)piperidine (16). The reaction is complete if less than 5 area % of 4-(2,3-dimethoxybenzoyl)-1-piperidinecarboxylic acid, 1,1-dimethylethyl ester (7) is detected.

Provenance & Evidence