Metal-Free Synthesis of 1-(α-Hydroxyindole)-o-carboranes in Neat

An efficient and environmentally friendly protocol for the synthesis of 1-(α-hydroxyindole)-o-carboranes has been developed via Friedel–Crafts reaction of C3-H of indoles with 1-formyl-o-carborane in the absence of Lewis acid and solvent. The intermolecular σ-π interaction between indole and B–H bonds of o-carborane was proposed for promoting the Friedel–Crafts reaction of the C3-H of indole.