A novel indole-2,3-epoxide equivalent, 2-hydroxyindoline-3-triethylammonium bromide, was found to be a convenient reagent for formal C3-electrophilic reactions of indoles with various nucleophiles. By taking advantage of the nucleophilic character of the oxygen of the 2-hydroxyindoline, the interrupted retro-Claisen and interrupted Feist-Bénary reactions with 1,3-dicarbonyl compounds were efficiently achieved.