Direct Transformation of Esters into Heterocyclic Fluorophores

Despite the manifold use of heterocyclic fluorophores, only a fraction of the desired dye diversity can be accessed by contemporary synthetic approaches. Herein, we describe a modular method that converts various carboxylic acid esters directly into a broad spectrum of heteroanthrylium fluorophores. The double addition of heteroatom-bridged 1,5-bifunctional organomagnesium reagents to esters leads to the formation of acridinium, xanthylium, and SiR fluorophores after dehydrative acidic work-up. This one-step synthetic method provides access to organophotoredox catalysts for dual catalysis with nickel and dyes amenable to fluorescence enhancement.