Acetic Anhydride → 1-[2-(2-Dimethylamino-ethyl)-benzo[b]thiophen-3-yl]-ethanone

Participants

Reaction Conditions

Reaction Steps

Compound 2a, [2-(3-bromo-benzo[b]thiophen-2-yl)-ethyl]-dimethyl-amine (17.5 mmol), was dissolved in anhydrous toluene (180 mL) and cooled to −78° C. Tetramethylethylenediamine (17.5 mmol) was added followed by n-BuLi (21.0 mmol, 1.6 M in hexanes). The mixture was stirred for 45 min at −78° C. Ac2O (70 mmol) was added and the mixture was allowed to slowly reach RT and was stirred overnight. The mixture was quenched with sat. NH4Cl, the pH of the aqueous layer was adjusted to 7-8 with sat. NaHCO3, and the reaction mixture was extracted with EtOAc (4×). The combined organic layer was washed with brine, dried over MgSO4, filtered and concentrated in vacuo. The crude material was purified by silica gel column chromatography in CH2Cl2 with a gradient up to CH2Cl2/MeOH=94/6 to afford Compound 6a, 1-[2-(2-dimethylamino-ethyl)-benzo[b]thiophen-3-yl]-ethanone (2.18 g, 50%); MS (MH+)=248.1.

Provenance & Evidence