Base-Promoted Ring Expansion Reaction of 4-Quinolones To Access Benzazepinones

4-Quinolone derivatives undergo an unexpected ring expansion reaction with α-halo esters/phosphonates/sulfones in the presence of a base, such as NaH, to produce novel benzazepinones. Under these mild and transition-metal-free conditions, most substrates gave moderate to excellent yields. The reaction could be applied in gram-scale synthesis of drug-like molecules that greatly accelerated our structure-activity relationship studies. A plausible mechanism was proposed.