Visible Light Excitation of BODIPYs Enables Dehydrogenative Enamination at Their α‑Positions with Aliphatic Amines

A photoredox-mediated
route to enamination of boron dipyrromethene
(BODIPY) dyes with aliphatic amines is reported by activating both
the β-C­(sp3)–H bond of amines and the α-C­(sp2)–H bond of BODIPYs under visible light illumination.
Dehydrogenation of amines by excited-state BODIPYs and/or photoredox
catalyst gave enamine intermediates, which were further trapped by
BODIPYs to give a series of α-enamineBODIPYs. These resultant
α-enamineBODIPYs showed red-shifted absorption and emission
maxima with ratiometric pH-dependent fluorescence.