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.