2-Substituted 3-Aryl- and 3-Heteroarylindoles by the Palladium-Catalyzed Reaction of<i>o</i>-Trifluoroacetanilides with Aryl Bromides and Triflates.
作者:Sandro Cacchi、Giancarlo Fabrizi、Doriano Lamba、Fabio Marinelli、Luca M. Parisi
DOI:10.1055/s-2003-38079
日期:——
The palladium-catalyzed reaction of aryl and heteroaryl bromides and triflates with o-alkynyltrifluoroacetanilides affords 2-substituted 3-aryl- and heteroarylindoles usually in excellent yield. The procedure can be applied to the synthesis of 2-substituted indole-3-carboxaldehydes.
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.