钯催化上乙酰基

A single-necked (24/40 joint) 250 mL round-bottomed flask is equipped with a Teflon-coated magnetic stir bar (4.0 x 1.5 cm, football-shaped). The apparatus is flame-dried under vacuum, then cooled to 23 ºC under an atmosphere of argon. The flask is charged sequentially with 6-bromobenzothiophene (8.00 g, 37.5 mmol, 1 equiv), cesium fluoride (22.8 g, 150 mmol, 4 equiv), and tetrakis(triphenylphosphine)palladium(0) (2.17 g, 1.88 mmol, 0.05 equiv) through the neck of the flask in singular portions. The neck of the flask is then fit with a rubber septum. An argon inlet needle and a purge needle are placed in the rubber septum, and the flask is purged for 5 min (Figure 1A). After 5 min, the vent needle is removed, and acetyltrimethylsilane (10.8 mL, 75 mmol, 2 equiv) is added in one portion over 1 min via a plastic syringe fit with an 18 G x 1.5'' needle. 1,2-Dichloroethane (38 mL, 1 M) is then added to the flask via a plastic syringe fit with an 18 G x 6'' needle in a single portion over 1 min (Figure 1B). The rubber septum is quickly removed and replaced with a separately flame-dried air condenser with a 24/40 joint. The reaction apparatus is then placed in an oil bath preheated to 75 ºC. The reaction mixture is stirred vigorously (800 RPM) for 24 h under positive argon pressure (Figure 1C).

After 24 h, the reaction flask is removed from the oil bath and allowed to cool to 23 ºC (Figure 1D). Once the reaction mixture is cooled to 23 ºC, the reflux condenser is removed, and the heterogeneous mixture is diluted with heptane (75 mL) . The solution is then filtered through a plug of silica gel (50 g, pre-wetted with 100 mL ethyl acetate) (Note  in a fritted Büchner funnel into a 1000 mL round-bottomed flask using ethyl acetate as eluent (500 mL)  filtrate is then concentrated under reduced pressure (31 °C, from 100 mmHg to 50 mmHg).

The resultant brown solid is purified via column chromatography using an OD 7.5 x 12 cm column of 250 g silica gel and eluted sequentially with 1400 mL 14:1 heptane:EtOAc and 2000 mL 9:1 heptane:EtOAc. The eluate is collected using 25 mL test tubes to provide the product in fractions 78-106. The fractions are combined in a collection flask and concentrated by rotary evaporation under reduced pressure (31 ºC, 90 mmHg). The material is then transferred to an 8-dram vial and dried under high vacuum for 30 min (<1 mmHg) to afford 6-acetylbenzothiophene (1) as a yellow powder (4.15 g, 63% yield).

标签： Acetylation