Alkali ion-controlled chemoselective indolation of allylic alcohols by base catalysis†

Although the transition-metal-catalyzed cascade reaction of allylic alcohols has achieved great success, there are rare selective examples that are catalyzed only by bases. Here, we present an efficient chemoselective catalytic system for the synthesis of valuable γ-indolation phenylpropanol and bis(indolyl)methane derivatives mediated by a transition-metal-free base and tuned through alkali metal ions. This protocol, which is applicable to a wide range of substrates with wide functional group tolerance, can be directly applied to gram-scale reactions and further transfers to useful intermediates. Experimental and theoretical studies have shown that cesium and sodium ions can precisely regulate the different hydrogen migration pathways of allylic alcohols.