Together with UV-Vis absorption spectra, fluorescent quenching study, light on-0ff experiments (see Supplementary Section S5) and literature precedence, plausible mechanisms were proposed as shown in Scheme 3D. First, upon light irradiation, the photocatalyst (PC, Ir(p-Me-ppy)3) is promoted to the excited state and engages in a single electron transfer with 2iodobenzoyl protected amine, affording PC •+ and transient aryl radical A after the loss of an iodide ion. Facile 1,5-HAT process translocates the radical to the -amino position, giving the key intermediate alkyl radical B. Then, PC •+ promotes the radical polar crossover through SET, delivering iminium intermediate C, along with the regeneration of the ground state photocatalyst. 14b Iminium C is readily captured by trialkyl phosphite through nucleophilic attack, giving phosphonium D, which is then dealkylated by iodide through an Arbuzov-type process to give the targeted -aminophosphonate (methyl iodide was observed as a byproduct, see Supplementary Section S5.4).