Merging photocatalysis with C-H insertions enabled switchable synthesis of indoles and indolines

C-H insertion offers a powerful route to C-C bond formation, yet it has often proven challenging to integrate into cascade synthetic sequences for further molecular elaboration. This limitation stems primarily from the aggressive conditions required for carbene generation and the high sensitivity of carbene species, which lead to premature termination and incapability with downstream transformations. Although intramolecular C-H insertion provides direct access to indolines, conventional approaches tend to produce ungoverned mixtures of indolines and indoles, owing to harsh conditions. To address these limitations, we develop a switchable synthetic platform that enables tunable access to either scaffold. By leveraging energy transfer, C-H insertions, and consecutive photoredox dehydrogenation, triplet carbene is accommodated in cascade reactions to afford N-fused indoles selectively. Conversely, the strategy can be switched to access indolines via singlet carbene-mediated C-H insertion. The incorporation of both motifs into drug scaffolds and natural products demonstrates their practical applicability. Based on the construction of a pseudo natural product (PNP) library featuring novel indole and indoline derivatives, tetracyclic indole alkaloid 5b is identified as a promising ferroptosis inhibitor after comprehensive pharmacological studies, underscoring the potential of PNP synthesis in drug discovery.