Boramidine: A Versatile Structural Motif for the Design of Fluorescent Heterocycles
Yury Lebedev, Chirag Apte, Susan Cheng, Cyrille Lavigne, Alan J. Lough, Alán Aspuru‐Guzik, Dwight S. Seferos, Andrei K. Yudin
Abstract
Sodium cyanoborohydride-derived N-alkylnitriliumboranes were found to be versatile precursors for the synthesis of novel boron-containing heterocycles. The reaction between N-alkylnitriliumboranes and 2-aminopyridines, imidazoles, oxazoles, or isoxazoles leads to the incorporation of the [B–C] motif into a five-membered boramidine, which exists as a mixture of Z and E isomers. The resulting heterocycles are blue fluorescent in both the solid state and in solution with ca. 2700–8400 cm–1 Stokes shifts and quantum yields in the 65–74% range in water and in the 42–84% range in organic solvents. The combination of photophysical properties, structural tunability, stability, and solubility in various media is expected to find application in a range of disciplines.