Mild, efficient, and solvent-free synthesis of 4-hydroxy-2-quinolinones

[Display omitted] •Anilines are converted to malonic acid monoanilides by reacting with Meldrum’s acid.•Malonic acid monoanilides are converted to 4-hydroxy-2-quinolinones by MSAA.•Malonic acid monoanilides are prone to decarboxylation above 70 °C.•The reactions require mild conditions (70 °C or lower). Malonic acid monoanilides were obtained in excellent yield from the reaction of anilines with Meldrum’s acid under solvent-free conditions. The malonic acid monoanilide intermediates were then treated with methanesulfonic acid anhydride (MSAA) to produce 4-hydroxy-2-quinolinones in excellent yield. It should be noted that both reactions had to be run under mild conditions to avoid the decarboxylation of the malonic acid monoanilide intermediate.