Regioselective Synthesis of Fluorescent Alkoxy-Substituted Phenazines and N-Alkyl Phenazinium Salts

Abstract

A method for the regioselective synthesis of 2,3,7,8-tetraalkoxyphenazines and N-alkyl phenazinium salts was developed. The protocol allows the synthesis of compounds with up to four different substituents at the designed positions. The synthesis was achieved using nonsymmetrically substituted 4,5-dialkoxy-2-nitroanilines and 1-bromo-2-nitrobenzenes via Buchwald–Hartwig amination, followed by tandem catalytic reduction and oxidative cyclization. The synthesized derivatives exhibit intense fluorescence in solution, with significant changes in spectroscopic properties induced by solvent polarity, the presence of acids, and changing the counterion in N-alkyl phenazinium salts.