Among 344 reactions of acetone α-arylation in a database, none is cobalt-initiated. Due to a unique confining environment, we stabilised a reactive metal centre and observed the αactivation of a series of ketones and their transfer from the cobalt centre onto the inner carbon atom of the two wellknown carbaporphyrins. The formation of a new C(sp 2 )-C(sp 3 ) bond within a macrocyclic crevice was possible due to the lability and reactivity of possible cobalt intermediates. The same bond could be cleaved while reacting with rhodium with a transfer of the acetone fragment on the metal centre. Functionalised macrocycles demonstrated peculiar keto-enol tautomerism with reversible formation of nonaromatic macrocyclic species after enol oxygen atom nucleophilic attack on the porphyrin's meso position. Simultaneously, they formed unique structural motifs, i.e., azuleno[1,2-c]pyran and 2,4dihydropyrano [3,4-c]pyrrole. The results not only offer a new paradigm for cobalt-induced chemistry in the macrocyclic confinement but also pave the way for exploring a broader spectrum of substrate activations and designing novel catalytic systems with tailored reactivity.