McLafferty-type β-fragmentation, formaldehyde is released and radical anion II is formed. Following a final SET process, a secondary amide is generated with concomitant regeneration of DIPEA: this is consistent with the observation that DIPEA can be used in substoichiometric amounts (Table , entry 10). The possibility of intermediate II directly reducing excited-state anthracene cannot be discounted. To establish that the process is redox neutral and that an aldehyde is generated, a Weinreb amide derivative with a modified (non-volatile) alkoxy group was exposed to the reaction conditions. The generation of the aldehyde in 69% is in line with the working hypothesis (Figure , part 1). To exclude the possibility of aldehyde formation via in-situ oxidation of the corresponding alcohol, various alcohols were exposed to the reaction conditions but no oxidation was observed (see ESI). To further support the involvement of a fragmentation mechanism, thereby distinguishing this from homolytic N-O bond cleavage, 21-24 a series of control experiments were performed. To exclude the possibility of alkoxy radical formation, a modified Weinreb amide with a pendant alkene was exposed to the standard conditions: both the product amide and aldehyde were formed in 73% and 56%, respectively with no cyclization product observed (Figure , part 2). The rates of such 5-exo-trig processes are known to be of the order of 6 x 10 8 s -1 . Furthermore, a control substrate that would enable an amidyl radical 23 to be intercepted was exposed to the general conditions (Figure , part 3) but heterocycle formation was not observed. Collectively, these experiments, together with example 2n (Figure ), support the postulated catalytic cycle. To exclude the involvement of a 1,5-HAT process, a cyclopropyl radical clock experiment was conducted but after subjecting this material to the standard conditions, no stereomutation was observed and the corresponding aldehyde was obtained (please see the ESI for full details). In addition, UV-measurements indicate that neither EDA complex formation nor the in situ formation of an organic dye 39 is a causative factor in the catalysis (see ESI). Since the reaction also proceeds without the use of DIPEA (table 1, entry 1), an alternative oxidative quenching cycle cannot be excluded (see ESI). Stern-Volmer fluorescence quenching studies indicate that the photocatalyst can be quenched by both DIPEA and the substrate Weinreb amide with similar levels of efficiency (see ESI), and thus this possibility cannot be discounted. To further expand the scope of photoinduced single electrontransfer process (PET) to include electron rich substrates, it was necessary to confront the current redox limitations of anthracene. To complement the existing bandwidth, a CV investigation of electronically distinct Weinreb amides was conducted (Figure ).