Base Promoted Synthesis of 4‐Quinolones Fused with Medium‐Sized Rings

Abstract In the presence of cesium carbonate, ynones bearing an ortho‐amino group reacted with cyclic β‐ketoesters through conjugated addition/carbon‐carbon σ‐bond cleavage/nucleophilic aromatic substitution tandem reaction to obtain 4‐quinolones fused with medium‐sized rings in good yields. This is the first example of synthesis of 4‐quinolones through base‐promoted insertion reactions of carbon‐carbon triple bonds into carbon‐carbon σ‐bonds. Notable features of this program are mild and transition‐metal‐free reaction conditions.