Curtius-Rearrangement Approach to 2,3-Substituted Indoles

Significance

Reported is a one-pot transformation of 2-iodobenzoic acid into 2,3- or 3-substituted indole derivatives via Curtius rearrangement/Pd-catalyzed indolization with acetylenic or aliphatic aldehyde substrates. Varying the base, either alkynes or aldehydes (ketones) could be used as substrates affording indoles in moderate to good yields. Treatment of the Curtius intermediates with amines led to the formation of ureas, which were subsequently cyclized to afford acylated indoles in poor to modest yields. In both reaction sequences, the substrate scope was sufficiently studied.