Domino Synthesis of 3-Alkyliden-2,3-Dihydro-4-Quinolones

The synthesis of 3-alkyliden-2,3-dihydro-4-quinolones has been accomplished in a domino fashion through a three-step sequence that comprised an initial aza-Baylis-Hillman reaction, followed by a 1,3-rearrangement and an intramolecular amination. Starting from readily available aryl vinyl ketones and N-tosyl imines, the reaction with PPh3, CsOAc and CuI in CH3CN gave rise, in good overall yields, to final 3-alkyliden-4-quinolone derivatives, valuable scaffolds in medicinal chemistry. The simultaneous addition of two bases, PPh3 and CsOAc, was found to be crucial for the success of the process. While PPh3 promoted the reversible aza-Baylis-Hillman reaction, CsOAc triggered the subsequent 1,3-rearrangement, which shifted the initial equilibrium and allowed to complete the synthetic sequence upon the addition of CuI.