Synthesis of 1,5-bifunctional organolithium reagents by a double directed ortho-metalation: Direct transformation of esters into 1,8-dimethoxy-acridinium salts

The impact of electronic and steric factors on the selectivity of the electrophilic aromatic substitution amounts to several limitations in accessing specific substitution patterns. Nucleophiles generated by directed metalation represent an effective alternative for the preparation of various distinctly substituted arenes and heterocyclic scaffolds to overcome these restraints. Herein, we report the direct synthesis of specifically substituted heterocyclic fluorophores from esters by the addition of 1,5-bifunctional organometallic reagents from a double directed ortho-metalation (dDoM). Bis(3-methoxyphenyl)amines were efficiently dilithiated and employed for the synthesis of 1,8-dimethoxy-acridinium salts with distinct photophysical and electrochemical properties. The individual reduction potentials, the water-solubility and the brightness of these new dyes promise different applications in catalysis, imaging and materials science. (C) 2018 Published by Elsevier Ltd.