Substitution, oxidation and addition reactions at C-7 of activated indoles

Abstract

4,6-Dimethoxy-2,3-diphenylindole (1) undergoes acylation, bromination, oxidative coupling and acid-catalysed addition to aldehydes at C-7 to produce a range of 7-substituted indoles (3-11), the indolo-isatin (6), the 7,7′-bi-indolyls (14), (16), (18), and the 7,7′-di-indolylmethanes (20-31). Addition to cyclopentanone gave compound (32), while Michael addition to α,β-unsaturated ketones gave compound (33) and the non-benzenoid double adduct (34). Related reactions led to the formation of the ring-fused indoles (39) and (41). Some reactions of the related indole diester (2) are also reported. © 1994.