To a cooled (0 ℃) solution of aluminum chloride (3 equiv) in DCM was added dropwise acetic anhydride (3 equiv) for 30 min. To the cooled mixture was added a suspension of the corresponding bromo indole (1 equiv) in DCM at 0 ℃ and the mixture was stirred at r.t. overnight. The reaction mixture was poured into ice saturated NH4Cl, and the aqueous layer was extracted with DCM. The organic extracts were washed with brine and dried over Na2SO4, and the residue was purified with flash column chromatography (SiO2, 0-20% EtOAc in hexane or 0-10% MeOH in DCM) to obtain the title compounds.