Visible-Light-Induced Carbonylation of Indoles with Phenols under Metal-Free Conditions: Synthesis of Indole-3-carboxylates

A visible-light-induced carbonylation of indoles with phenols for the synthesis of indole-3-carboxylates has been developed. The reaction proceeded via a radical carbonylation process in which elementary I₂ was used as an effective photosensitive initiator and, thus, avoided the use of transition metal catalysts. A series of different aryl indole-3-carboxylates were prepared in moderate to good yields. The broad applicability of this methodology was further highlighted by the late-stage functionalization of several phenol-containing natural products and pharmaceuticals.