The first general method for the synthesis of 4H-1,3-benzodioxin-2-one derivatives has been developed. Treatment of t-butyl 2-vinylphenyl carbonates with iodine in the presence of sodium hydrogencarbonate gave 4-iodomethyl-4H-1,3-benzodioxin-2-one derivatives in moderate to good yields. These iodides were reduced with tributyltin hydride to give the corresponding 4-methyl-4H-1,3-benzodioxin-2-one derivatives.