Transition-Metal-Free Cascade Synthesis of 4-Quinolones: Umpolung of Michael Acceptors via Ene Reaction with Arynes

A novel one-pot aryne transformation is described that affords various 4-quinolone derivatives without recourse to transition-metal catalysis. Arynes react with aza-Morita-Baylis-Hillman (AMBH) adducts through a cascade sequence involving an insertion/cyclization/ene reaction process to afford 4-quinolones in high yields with a broad substrate scope under mild reaction conditions. Essentially, an umpolung of reactivity at the beta carbon of alpha,beta-unsaturated ketone has been achieved by an inverse electron demand aryne-ene reaction to provide a C-arylated product.