Switchable skeletal editing of quinolines enabled by cyclizative sequential rearrangements.

The rapid diversification of core ring structures in complex molecules through switchable skeletal editing is valuable in the drug discovery process. However, controllable methods for chemically divergent modifications of azaarene frameworks using common substrates are challenging, despite the potential to maximize structural diversity and complexity. Here we report the tunable skeletal editing of quinolines through Brønsted acid-catalysed multicomponent reactions of quinoline N-oxides, dialkyl acetylenedicarboxylates and water to generate nitrogen-containing heteroaromatic compounds together with linear compounds in a modular fashion. Specifically, in a one-pot procedure, after cyclization and sequential rearrangement processes, the quinoline N-oxides are easily converted into unique 2-substituted indolines. These then undergo acid-promoted fragmentation to give indoles, base-facilitated ring-opening to afford 2-alkenylanilines and oxidative cyclization to yield isoquinolinones. Catalytic asymmetric skeletal editing of quinolines is also realized, providing enantioenriched benzazepines bearing quaternary stereocentres, and late-stage skeletal modification of quinoline cores in several drugs is demonstrated.