In a model experiment, a 0.1 M solution of 1a and 1 mol% of a PC were charged into a 5-mm NMR tube (Figure , extended optimization in the SI). The mixture was degassed by freezepump-thaw and then irradiated with a household blue LED strip. The consumption of 1a required 168 hours (entry 1). A meagre 22% yield of 2a was observed and the product partially decomposes through time in the presence of light and the photosensitizer. No improvement was achieved by varying the solvent, the catalytic charge, and/or the concentration of the mixture. However, the full conversion of 1a was obtained upon a halved irradiation time in the presence of 30 mol% of a N derivative (entries 2-5). A higher yield of 2a was observed using N4, which had a flexible tether between its two naphthyl groups. Different Ir(III) complexes (entries 6-7) and organic photosensitizers did not improve the outcome. The substrate was fully converted upon 36 hours of irradiation using the commercially-available PC4 in combination with purple LEDs (entry 8). The best result was achieved combining N4 and PC5, which we easily synthesized (entries 9-10). The complex has not been previously used in EnT methods despite its high ET, due to electron-poor C,N ligands and an electron-rich N,N one, and its long-lived (t) triplet state, together, suggest that it could be a more powerful tool than the popular PC4. No traces of 2a were formed without the PC or the light source. The conversion of 1a was slightly slower in the presence of oxygen. 20 Allenamides were prepared by sequential reductive amination, acylation and isomerization. This route tapped into an ample reservoir of readily-available aldehydes and acylating species. Either azetidines or b-lactams could be thus accessed in a Lego-like fashion (Figure ). The acetyl unit of 2a could be replaced by a methacryloyl fragment with minimal loss of efficiency (2b), and no polymerization took place. A strained cyclopropyl arm and terminal aolefins were similarly tolerated (2c-d). The presence of an arylamide did not hamper the reaction (2e-h). Best results were achieved with electron -neutral and -rich (hetero)aryl rings, while a slightly lower yield was observed with electron-poor systems. The amido group could be replaced by a carbamate one (2i), which could be easily cleaved. The product was retrieved in a synthetically useful yield and the reaction could be scaled up to 1 mmol. The variation at the b-carbon was then assessed. A tertiary C(sp 3 )-H bearing one aryl substituent can undergo the functionalization despite a higher BDE (2j). The steric demand of the acyl group was more relevant in this case (2k). The presence of substituents on the aryl ring led to the formation of products in moderate yield (2l-2o).