Prompted by the observed catalytic activity differences between CD-1 and CD-2, we conducted further mechanistic investigations. Both the radical addition and cyclization reactions were completely suppressed in the presence of the radical quencher TEMPO (5 mol%), confirming their highly dependence on radical-mediated HAT processes (Fig. ). Notably, CD-1 and CD-2 retained their respective reactivity preferences and exhibited only a slight reduction in yields when 5 mol% tetramethyl ammonium chloride adduct was introduced (Fig. ), suggesting that presence of molecular alkyl ammonium cations in the solution phase does not alter the photoredox property of CDs photocatlysts, and therefore would not influence the catalytic behavior.