Acetylation of 3-acetylindole (9) with acetyl chloride-aluminum chloride in nitrobenzene or methylene chloride gave 3, 5-diacetylindole (10) as the major product, together with 3, 6- and 3, 7-diacetylindole (11, 12) as minor products. The similar acetylation of ethyl 3-indolecarboxylate (16) also gave the 5-acetyl derivative (17a) as the major product, together with the 6-and 7-acetyl derivatives (18a, 19) as minor products. Oxidation of 1, 3-diacetylindole (15) with lead tetratrifluoroacetate gave 3-indolinones (22, 23) and a dimeric product (24).
