Considering cost and ease of reaction, we planned to synthesize BASN starting with simple condensation of readily-accessible iodoanilines and aryl sulfonyl chlorides, followed by radical cyclization (see section 5.1 of Supporting Information, SI, for retrosynthesis and cost analysis). At the onset of the study, we investigated the reductive radical cyclization of tosylated o-iodoaniline 1a induced by SET reduction of the aryl iodide by a radical anionic organophotocatalyst generated upon visible light irradiation (Figure ). Catalytic loadings of 4CzIPN or NpMI gave BASN product 2a in 52% and 50% respectively. However, we were surprised that the reaction worked even without a photocatalystaffording 2a in 34%. Even more so, the yield of 2a improved (to 40%) by irradiation of the reaction mixture containing only 1a and tributylamine (i.e., in the absence of a photocatalyst and an inorganic base). After design of experiment (DoE) optimization and further screening of conditions (see section 5.2 of SI for full details), we identified that the use of N,N-dimethylethanolamine (DMEA) under blue light irradiation (h = 450 nm) afforded 2a in a high yield (84%) within short reaction time of 3 h. Furthermore, fluorine-containing BASN 2b, was accessed in excellent yield (91%) under these conditions. Control reactions confirmed that both light and DMEA are crucial for this transformation. Intrigued by the efficiency of this reaction and the fact that exogenous photocatalyst is not required, the mechanism was then probed (see section 6 of SI for full mechanistic analysis). The reaction profile for the consumption of 1b / formation of 2b (monitored using F-NMR) displayed a sigmoidal shape (Figure ) and its second derivative fits a parabolic trend (see SI, Figure ). This establishes that the reaction has three phases: slow initiation, acceleration (with the maximum rate reach when [1b] = [2b]), and a saturation phasehallmarks of an autocatalytic process . To check this, we performed the unequivocal test for autocatalysis which involves the effect of the adding product on the initial rates . Therefore, 2a was added at increasing catalytic loadings: 0 mol%, 10 mol%, and 20 mol% (Figure ). Indeed, the initial rate for formation of 2b (i.e., slope of the yield as a function of time) increases as the loading of BASN 2a. UV-Vis spectroscopy revealed that the deprotonated product is the most light absorbing species at the blue region tailing until ca. 450 nm, catching the tail end of the emission of the 450 nm LED employed(Figure ). H-NMR studies confirmed that the sulfonamide moieties of 1 and 2 are deprotonated under the reaction conditions, consistent with the pKas of arylsulfonamides (pKa of 1a = 8.1 and pKa of 2a = 8.9,) and DMEA (pKaH = 9.23) . Taken together, we propose that deprotonated 2 is the active photocatalyst in its own autocatalytic synthesis that engages 1 in electron transfer. Consistent with this proposal, testing an N-methylated sulfonamide that cannot be deprotonated afforded 3a (vide infra) only in trace amounts.