Studies on Tertiary Amine Oxides. LXXI. Some Electrophilic Reactions of 1-Hydroxy-2-phenylindole

Treatment of 1-hydroxy-2-phenylindole (1) with phosphoryl chloride-DMF gave 2-phenylindole-3-carboxaldehyde (2) in 70% yield. The reaction of 1 with quinoline 1-oxide (3) and benzoyl chloride in boiling chloroform produced 1-benzoyloxy-2-phenyl-3-(2-quinolyl) indole (5) and 1-hydroxy-2-phenyl-3-(2-quinolyl) indole (6). In the reaction using tosyl chloride instead of benzoyl chloride, 6 or 2-phenyl-3-(2-quinolyl) indole (8) was formed. These results demonstrate that the enehydroxylamine systems in 1 and 1-benzoyloxy-2-phenylindole (4) can behave as nucleophilic species as a result of enamine-like polarization.