Mechanoresponsive Carbamoyloximes for the Activation of Secondary Amines in Polymers

Mechanophores are molecular moieties that are incorporated into polymers and respond to force with constitutional, configurational, or conformational bond rearrangements to enable functionality. Up to today, several chemically latent motifs have been activated by polymer mechanochemical methods, but the generation of secondary amines remains elusive. Here we report carbamoyloximes as mechanochemical protecting groups for secondary amines. We show that carbamoyloximes undergo force-induced homolytic bond scission at the N-O oxime bond in polymers thus producing the free amine, as the reaction proceeds via the carbamoyloxyl and aminyl radicals, analogously to its photochemical counterpart. Eventually, we apply the carbamoyloxime motif in a force-activated organocatalytic Knoevenagel reaction. We believe that this protecting strategy can be universally applied for many other secondary and primary amines in polymer materials.