Recent Advances in Skeletal Editing of Indoles to Prepare N-Heterocycles.

Skeletal editing has emerged as a transformative strategy in modern organic synthesis, enabling direct and precise modification of molecular frameworks to access diverse chemical space. This review summarizes advances in the skeletal editing of indoles over the past five years, a privileged scaffold ubiquitous in bioactive molecules and natural products. We focus on three principal strategies: (i) carbon-atom insertion via cyclopropanation/ring expansion sequences to furnish quinolines, often employing carbene precursors; (ii) nitrogen-atom insertion using nitrene or related reactive amine species to access quinazoline and quinoxaline cores; and (iii) ring-opening and subsequent recombination to construct polycyclic N-heterocycles. These methodologies are summarized in terms of their mechanistic pathways, substrate scopes, and functional group compatibilities. This review highlights skeletal editing as a powerful and step-economical routes to complex and valuable N-heterocycles that are difficult to be obtained through the traditional peripheral functionalization, offering new opportunities for drug discovery and materials science.