Reaction development. Considering both iminyl and amidyl radicals are two types of widely-explored N-centered radicals, showing ambiphilic and electrophilic properties, respectively, our investigation commenced with the development of iminyl and amidyl-containing bifunctional nitrogen-radical precursors. As shown in Fig. , various unprecedented oxime ester-based nitrogen-radical precursors were synthesized for the first time, and their reactivities were examined under visible-light-sensitized conditions by using tert-butyl 1H-indole-1-carboxylate H1 as N-centered radical acceptor. We hypothesized that these precursors could undergo a N-O bond fragmentation through photosensitization to their triplet excited state via EnT catalysis, resulting in iminyl and amidyl radicals along with the release of CO 2 and aldehyde/ketone. Indeed, the desired dearomative diamination reactions of H1 with a series of bifunctional nitrogen-radical precursors S1-S10 were observed in the presence of a cheap and commercially available thioxanthone as photosensitizer (5.0 mol %), after irradiation for 12 h with blue LEDs (18 W, λ max = 405 nm) in acetone. To our delight, the desired vicinal diamine product 8 was obtained in 72% isolated yield with excellent regio-and diastereoselectivity when employing Troc-protected bifunctional reagent S8. Reasonably, the monomethyl or α-unsubstituted Troc-protected bifunctional reagents S9 and S10 gave a reduced outcome of product 8, likely because of the fact that the α-substituents may increase the rate of the radical decarboxylation step. Replacement of the benzophenone iminyl with a phthalimidyl unit (S11 and S12), the transformation was shut down completely, suggesting that the benzophenone iminyl radical with a relatively long lifetime played a critical role for the dearomative diamination. In order to further understand the reactivities of these bifunctional reagents, their triplet energies were determined by DFT calculation, ranging from 46.8 to 64.7 kcal mol -1 (Fig. , see Supplementary Information for the details). Given the triplet energy of thioxanthone was previously reported as 65.5 kcal mol -1 , energy transfers from thioxanthone to S1-S12 are all thermodynamically feasible. To explore the lack of reactivity of S11 and S12, the spin density distributions of the triplet states were determined (Fig. , see Supplementary Information for the details). As for both species, the spin density is predominantly localized on the phthalimide functionalities, it is expected that a high energy barrier has to be overcome to enable homolytic N-O bond breaking. In addition, the reaction of H1 with S8 was analyzed by GC-MS measurement to elucidate the composition of reaction mixtures (Fig. , see Supplementary Information for the details). S8 was completely consumed, given its high reactivity to generate a pair of N-centered iminyl and amidyl radicals under the standard reaction conditions. The protonation of both N-centered iminyl and amidyl radicals, as well as the homo-coupling reaction of persistent N-centered iminyl radical were the main side-reactions observed in the reaction. Meanwhile, small amount of 1H-indole was also observed in the reaction mixtures, resulting from the deterioration of H1. Subsequently, the impact of other reaction parameters was also investigated (Fig. ). As expected, this transformation did not proceed in the absence of either thioxanthone or blue light (Fig. , entries 1-2). Satisfactorily, product 8 could be obtained in 48% yield when reducing the loading of thioxanthone to 1.0 mol % (Fig. , entry 3). The reaction appeared to be less sensitive to the solvents, as replacing acetone with EtOAc, CH 2 Cl 2 , or THF as solvent still furnished 8 in moderate to good yields (Fig. , entries 4-6). Moreover, different photocatalysts were screened, and the [Ir(dF(CF 3 )ppy) 2 (dtbbpy)](PF 6 ) complex was also proven to be a suitable catalyst for this dearomative diamination without diminishing the outcome. Furthermore, screening of the ratio of H1 and S8 were conducted under the standard conditions (Table , see Supplementary Information for the details). Either reducing the dosage of H1 or switching the stoichiometry of H1 and S8 led to diminished yields of 8 (Table , entries 1-5), likely because of the deterioration of H1 in the reaction. Finally, a conditions-based sensitivity screening suggested that this protocol was less sensitive towards the concentration of substrates, moisture, and scale-up, only suffering from slightly diminished yields at high oxygen concentration or low light intensity (see Supplementary Information for the details). 60 Mechanistic investigations. To get some insights into this dearomative diamination, a series of mechanistic studies were performed. Firstly, the reaction of H1 and S8 was completely inhibited by adding 2.0 equivalent of TEMPO as a radical scavenger, and the TEMPO-adduct 9 and radical-radical cross-coupled product 10 were detected by HRMS measurement, and products 11-13 were observed as the major byproducts by GC-MS measurement (Fig. and S10, see Supplementary Information for the details). These results clearly hinted towards the radical nature of the reaction, and also demonstrated the generation of iminyl and amidyl radicals (Fig. ). Secondly, the reaction of S8 with A38 under standard conditions formed a cyclic product 14 in 22% yield, further suggesting the involvement of two N-centered radicals (Fig. ).