Au(I)-Catalyzed Regioselective Hydrogen Isotope Labeling of Indoles.

The gold(I)-catalyzed hydrogen isotope exchange reaction on indoles and related heterocycles is described under mild conditions and low catalyst loadings, using CDOD and DO as readily available deuterium sources. C3-unsubstituted indoles are labeled at the C3 position with exquisite regioselectivity, while C3-substituted indoles are labeled at the C2 position. The method is also applicable to the regioselective tritiation of indoles. Mechanistic studies revealed the involvement of aurated indoles as key intermediates.