反应详情

A solution of 8.7 g of 6,7-dichloro-5-hydroxybenzo[b]thiophene in 50 ml of anhydrous tetrahydrofuran is placed in a 250 ml 3-necked flask and cooled to -25°. To the solution under nitrogen, is added dropwise 42 ml of a solution of 2.5M n-butyllithium at a rate such that the temperature did not rise above -10°. After total addition, the mixture is stirred at 0°-5° for 3 hrs. To the mixture is added 14 ml of anhydrous dimethylformamide over a period of 20 mins. The reaction mixture is allowed to warm to room temperature and stirred for 1 hr. Quenching with 400 ml of 2N hydrochloric acid, followed by extraction with ethyl acetate, gives a precipitate. Recrystallization from acetone-hexane affords 6.5 g of 6,7-dichloro-2-formyl-5-hydroxy-benzo[b]thiophene, mp 197°-198°.

1. temperaturecooled to -25°
2. customdid not rise above -10°
3. additionAfter total addition
4. stirringstirred for 1 hr
5. customQuenching with 400 ml of 2N hydrochloric acid
6. extractionfollowed by extraction with ethyl acetate
7. customgives a precipitate
8. customRecrystallization from acetone-hexane