Transition‐Metal‐Free Deconstructive Lactamization of Piperidines

One of the major challenges in organic synthesis is the activation or deconstructive functionalization of unreactive C(sp 3 )–C(sp 3 ) bonds, which requires using transition or precious metal catalysts. We present here an alternative: the deconstructive lactamization of piperidines without using transition metal catalysts. To this end, we use 3‐alkoxyamino‐2‐piperidones, which were prepared from piperidines through a dual C(sp 3 )–H oxidation, as transitory intermediates. Experimental and theoretical studies confirm that this unprecedented lactamization occurs in a tandem manner involving an oxidative deamination of 3‐alkoxyamino‐2‐piperidones to 3‐keto‐2‐piperidones, followed by a regioselective Baeyer–Villiger oxidation to give N ‐carboxyanhydride intermediates, which finally undergo a spontaneous and concerted decarboxylative intramolecular translactamization.