Visible Light-Induced Decarboxylative Alkylation of Heterocyclic Aromatics with Carboxylic Acids via Anthocyanin as a Photocatalyst

A visible light-induced decarboxylative alkylation of heterocyclic aromatics with aliphatic carboxylic acids was developed by using anthocyanins as a photocatalyst under mild conditions. A series of alkylated heterocyclic compounds were obtained in moderate to good yields by using the metal-free decarboxylative coupling reaction under blue light. This strategy uses cheap and readily available carboxylic acids as alkylation reagents with good functional group tolerance and environmental friendliness. It is worth noting that this is the first time that anthocyanin has been used to catalyze the Minisci-type C-H alkylation. The mechanism of decarboxylation alkylation was studied by capturing the adduct of alkyl radical and hydroquinone, thus confirming a radical mechanism. This protocol provides an alternative visible light-induced decarboxylative alkylation for the functionalization of heterocyclic aromatics.