From the UV-Vis, cyclic voltammetry (CV), and emission experiments, it was estimated that *BASNs 2a - and 2b -can reach excited state redox potentials of -2.45 V and -2.31 V versus SCE respectively (see section 6.5 of SI). A quantum yield measurement of less than 0.5% suggests a radical chain mechanism is unlikely . From these experiments, we propose the following photoredox autocatalytic cycle (Figure ). After deprotonation of the starting material i, a mildly photo-absorbing anionic intermediate i -is excited by light. A concerted dissociative SET from DMEA or another equivalent of i -generates aryl radical intermediate ii, followed by de-aromative ortho cyclization to form iii. Rearomatization by SET and deprotonation or by HAT affords a deprotonated BASN -product, marking the end of a slow initiation phase. Once the BASN -is present in the system, this acts as an autocatalyst for a redox-neutral cyclization of another equivalent of i -, intercepting the catalytic cycle again after aryl radical generation and re-aromatization. This autocatalytic phase is faster as i) BASN -has the most efficient absorption at the blue region, ii) packs the highest reductive redox power in its excited state, and iii) the photocatalyst concentration increases with every turnover.