1,4-Dihydropyridine compounds as versatile dehalogenation reagents under visible-light irradiation

1,4-Dihydropyridine (DHP) anions, when excited by visible light, have been used as dehalogenation reagents or as precursors of formal hydrogen radicals, enabling the sequential dehalogenation of polyhalogenated compounds in the order I > Br > Cl. The dehalogenative functionalization reaction was accomplished by identifying the particular DHP derivative and its optimal amount that could suppress the hydrodehalogenation pathway.