Preparation of Halogenated Fluorescent Diaminophenazine Building Blocks

Matthieu Koepf, Shin Hee Lee, Bradley J. Brennan, Dalvin D. Méndez-Hernández, Victor S. Batista, Gary W. Brudvig, Robert H. Crabtree

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Abstract

A short, convenient, and scalable protocol for the one-pot synthesis of a series of fluorescent 7,8-dihalo-2,3-diaminophenazines is introduced. The synthetic route is based on the oxidative condensation of 4,5-dihalo-1,2-diaminobenzenes in aqueous conditions. The resulting diaminophenazines could be attractive intermediates for the preparation of polyfunctional phenazines and extended polyheteroacenes. We find that the undesired hydroxylation byproducts, typically obtained in aqueous conditions, are completely suppressed by addition of a stoichiometric amount of acetone during the oxidation step allowing for selective formation of 7,8-dihalo-2,2-dimethyl-2,3-dihydro-1H-imidazo[4,5-b]phenazine derivatives with good to excellent yields. Under reductive conditions, the imidazolidine ring can be hydrolyzed into the desired 7,8-dihalo-2,3-diaminophenazines. Furthermore, we report a selective route under highly reducing conditions to monohydrodeaminate the 2,3-di(methylamino) phenazine derivatives, which allows for further structural variations of these phenazine building blocks. All of these derivatives are luminescent, with measured fluorescence quantum-yields of up to 80% in ethanol for the more rigid structures, highlighting the potential of such materials to provide new fluorophores.

Original languageEnglish
Pages (from-to)9881-9888
Number of pages8
JournalJournal of Organic Chemistry
Volume80
Issue number20
DOIs
Publication statusPublished - Oct 16 2015

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ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Koepf, M., Lee, S. H., Brennan, B. J., Méndez-Hernández, D. D., Batista, V. S., Brudvig, G. W., & Crabtree, R. H. (2015). Preparation of Halogenated Fluorescent Diaminophenazine Building Blocks. Journal of Organic Chemistry, 80(20), 9881-9888. https://doi.org/10.1021/acs.joc.5b01339