Hydrochloric Acid → 5-Methyl-6-(4-methylphenylsulphonyl)-1,3-benzodioxole-2-carboxylic acid ethyl ester

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Reaction Steps

A suspension of 12.0 g (43.1 mmol) of 4-methyl-5-(4-methylphenylsulphonyl)-1,2-benzenediol and 30 g (216 mmol) of freshly calcined potassium carbonate in 200 ml of dry 1,2-dimethoxyethane is stirred for 5 minutes, under nitrogen, using a high-speed stirrer. In the course of this the temperature rises to 75°. Then, while stirring moderately (propeller stirrer), there is added dropwise thereto, in the course of one hour, a solution of 6.77 g (43.1 mmol) of dichloroacetic acid ethyl ester in 50 ml of dry 1,2-dimethoxyethane and the mixture is then boiled under reflux for 15 hours. It is subsequently poured onto an ice/water mixture and adjusted to pH 1-2 with concentrated hydrochloric acid. Some of the 1,2-dimethoxyethane is evaporated off in a rotary evaporator and the solution remaining is extracted with ethyl acetate. The combined organic phases are washed with water and saturated sodium chloride solution, dried over sodium sulphate and concentrated by evaporation in a rotary evaporator. The resulting black oil is dissolved in ethanol, 0.5 g of p-toluenesulphonic acid is added, and the whole is boiled under reflux in a vessel provided with a Soxhlet attachment that is filled with molecular sieve. The ethanolic solution is then concentrated completely by evaporation and chromatographed over silica gel (solvent ethyl acetate/hexane in a ratio of 1:1). The uniform fractions containing the desired substance are combined and concentrated by evaporation. In this manner 5-methyl-6-(4-methylphenylsulphonyl)-1,3-benzodioxole-2-carboxylic acid ethyl ester is obtained in the form of a yellow oil, which can be hydrolysed directly.

Provenance & Evidence