Hydrochloric Acid → 2-Acetyl-6,7-dichloro-5-methoxybenzo[b]thiophene

Participants

Reaction Steps

To a solution of 5.0 g of 6,7-dichloro-5-methoxybenzo[b]thiophene in 30 ml of dry tetrahydrofuran and 10 ml dry ethyl ether under nitrogen at -20° is added 11.7 ml of 2.2M n-butyllithium, while the temperature is maintained at -20°. After stirring for 2 hours at this temperature, the reaction mixture is added dropwise through a transfer needle to a stirred solution of 22 ml of freshly distilled acetic anhydride in 40 ml of dry tetrahydrofuran at -20°. Five minutes after the addition, the reaction mixture is poured onto 100 ml 10% hydrochloric acid. The mixture is extracted twice with dichloromethane, the organic layers are collected and dried and the solvent is removed to give a solid. The solid is washed with ethyl ether to give 1.5 g of 2-acetyl-6,7-dichloro-5-methoxybenzo[b]thiophene as a fluffy solid. Recrystallization of the residue obtained by evaporation of the filtrate from ethyl ether-hexane gives an additional 0.6 g of 2-acetyl-6,7-dichloro-5-methoxybenzo[b]thiophene.

Provenance & Evidence