Synthesis of Water-Soluble Blue-Emissive Tricyclic 2-Aminopyridinium Salts by Three-Component Coupling-(3+3)-Anellation

Abstract

The (3+3) anellation of alkynones and cyclic amidines is a novel and unexpected approach to generate intensively blue luminescent tricyclic 2-aminopyridinium salts with quantum yields Φ_f up to 63 % in water. By implementation into a consecutive three-component reaction, these title compounds are obtained rapidly and efficiently in a diversity-oriented fashion. Most interestingly, these bi- and tricyclic 2-aminopyridinium salts emit in dichloromethane and water solutions, thus making them interesting novel luminophore probes for bioanalytics, as well as in the solid state, thus making them blue emitters with tunable efficiency.

Keywords: alkynylation; catalysis; cross-coupling; fluorescence; multicomponent reaction.