A New Methodology for Functionalization at the 3-Position of Indoles by a Combination of Boron Lewis Acid with Nitriles

We discovered that a reagent comprising a combination of PhBCl2 and nitriles was useful for syntheses of both 3-acylindoles and 1-(1H-indol-3-yl)alkylamine from indoles. The reaction proceeded selectively at the 3-position of indoles providing 3-acylindoles in moderate to high yields on treatment with the above reagent. Furthermore, the reaction provided the corresponding amine products in moderate to high yields after the intermediate imine was reduced by NaBH3CN. These reactions proceeded under mild conditions and are applicable to the formation of indoles functionalized at the 3-position.