Synthesis of diverse indole-containing scaffolds by gold(I)-catalyzed tandem reactions of 3-propargylindoles initiated by 1,2-indole migrations: scope and computational studies

摘要

Similar to propargylicudcarboxylates and sulphides, 3-udpropargylindoles undergo 1,2-indoleudmigrations under cationic gold(I)-udcatalysis. The intermediate Aucarbenoidudcomplex may evolve throughuddifferent pathways depending on theudsubstituents at the propargylic andudterminal positions of the alkyne moiety.udThus, 3-indenylindole derivatives wereudeasily obtained through formal iso-udNazarov or Nazarov cyclizations. DFTudcomputations support the formation ofudan alkylidenecyclopropane intermediateudthat undergoes aura-iso-Nazarov orudaura-Nazarov cyclizations uponudtorquoselective ring opening. Inudaddition, 3-dienylindoles could beudaccessed when none of the referredudpathways were accessible and so theudintermediate Au-carbenoid complexudevolved via a 1,2-CH insertionudreaction. We have also demonstratedudthat the final products can be obtainedudin a one-pot protocol from easilyudavailable propargylic alcohols andudindoles