A facile and general synthesis of 2, 2-dimethyl-1, 3-dioxin-4-one derivatives (1) is reported. Treatment of β-keto acids with a mixture of acetone, acetic anhydride, and conc. sulfuric acid or with a mixture of isopropenyl acetate and conc. sulfuric acid gave 2, 2-dimethyl-1, 3-dioxin-4-ones (1). Similar treatment of tert-butyl esters of β-keto acids also gave 1.