Nitrogen editing of aromatic rings: from skeletal editing to fragment editing

Direct conversion of aromatic rings into heteroaromatic frameworks represents an attractive strategy for tuning molecular properties in pharmaceuticals and functional materials. In recent years, the concept of molecular editing has emerged as a powerful approach that enables such transformations without reconstructing the entire aromatic framework. In this Feature Article, we discuss two complementary strategies for nitrogen incorporation into aromatic systems based on different editing units: atom-level skeletal editing and aromatic-unit fragment editing. Skeletal editing modifies aromatic frameworks through single-atom transformations such as carbon-to-nitrogen transmutation and ring-expansion-type nitrogen insertion. In contrast, fragment editing reorganizes molecular structures through exchange of aromatic fragments enabled by reversible bond activation processes, including single-bond metathesis-type reactions, shuttle-type reactions, and heteroaromatic swapping reactions. By comparing these approaches from the perspective of molecular design, this review highlights how aromatic identities can be reorganized through distinct editing units and discusses future opportunities for fragment-level editing of heteroaromatic frameworks.