Switchable Access to 3-Carboxylate-4-quinolones and 1-Vinyl-3-carboxylate-4-quinolones via Oxidative Cyclization of Isatins and Alkynes

An efficient transition-metal-free oxidative cyclization reaction using isatins and alkynes for the facile synthesis of structurally diverse 4-quinolones has been developed. Intriguingly, switchable access to substituted 3-carboxylate-4-quinolones and 1-vinyl-3-carboxylate-4-quinolones could be achieved by choosing a different base in the reaction. The obtained products could undergo further transformations, increasing the application potential of the method in organic synthesis.