4-Amino-2-chlorobenzoic acid → 2-Chloro-4-hydroxybenzoic acid

Participants

Reaction Conditions

Reaction Steps

In a solution of 10 ml of concentrated sulforic acid in 30 ml of water was dissolved 10 g of 4-amino-2-chlorobenzoic acid, the solution was reacted under reflux for 1 hour, and the thus obtained solution was cooled to 5° C. Then, 4.6 g of sodium nitrite and 20 ml of water were added to the solution and the mixture was refluxed for 5 hours and cooled. The precipitated crystal was recovered by filtration and washed with water to obtain 6.0 g of 4-hydroxy-2-chlorobenzoic acid. Then, 3 g of this 4-hydroxy-2-chlorobenzoic acid was dissolved in an aqueous solution of sodium hydroxide, 10 g of n-dodecyl bromide was added to the solution, and reaction was carried out at 80° C. for 5 hours with stirring. The thus-obtained solution was put in ice-cooled hydrochloric acid. Precipitated 4-dodecyloxy-2-chlorobenzoic acid was recovered by filtration, washed with water, dried and dissolved in dichloromethane. Then, 2.0 g of p-benzyloxyphenol and 2.0 g of dicyclohexylcarbodi-imide were added to the solution, and reaction was carried out at room temperature with stirring overnight. The precipitate was recovered from the thus-obtained solution by filtration, concentrated and purified by the silica gel column chromatography to obtain 2.3 g of 4-benzyloxyphenyl 4-dodecyloxy-2-chlorobenzoate. This product was catalytically reduced in the presence of Pd/C as the catalyst under a hydrogen pressure of 1 kg/cm2 according to customary procedures to obtain 2.0 g of 4-hydroxyphenyl 4-dodecyloxy-2-chlorobenzoate.

Provenance & Evidence