title: Preparation of Halogenated Fluorescent Diaminophenazine Building Blocks.
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.
authors.affiliation: Energy Sciences Institute, and Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Koepf
authors.affiliation: Energy Sciences Institute, and Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
authors.forename: Shin Hee
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Energy Sciences Institute, and Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Brennan
authors.affiliation: Energy Sciences Institute, and Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
authors.forename: Dalvin D
authors.initials: DD
authors.lastname: Méndez-Hernández
authors.affiliation: Energy Sciences Institute, and Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
authors.forename: Victor S
authors.initials: VS
authors.lastname: Batista
authors.affiliation: Energy Sciences Institute, and Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Brudvig
authors.affiliation: Energy Sciences Institute, and Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Crabtree