Figure 1: Activation modes in carbene organic catalysis.

(a) Previous studies mainly dealt with carbon atom activation for acyclic non-aromatic carbonyl compounds. (b) Our earlier studies realized indole-type heteroaryl aldehyde benzylic carbon activation. (c) Addition of carbene catalyst eventually leads to simple phenyl aldehyde activation which induces phenol oxygen atom functionalization via a new azolium-bound intermediate (II).