3-Methyl-2-buten-2-yl triflate (CAS NO.: ), which is known as sulfonic acid, trifluoro-, 1,2-dimethyl-1-propenyl ester, could be produced through the following synthetic routes.

A. . A dry, 100-ml., round-bottomed flask is charged with 36.3 g. (0.242 mole) of trifluoro and 27.3 g. (0.192 mole) of phosphorus pentoxide. The flask is stoppered and allowed to stand at room temperature for at least 3 hours. During this period the reaction mixture changes from a slurry to a solid mass. The flask is fitted with a short-path distilling head and heated first with a stream of hot air from a heat gun and then with the flame from a small burner. The flask is heated until no more trifluoromethanesulfonic anhydride distills, b.p. 82–115°, yielding 28.4–31.2 g. (83–91%) of the anhydride, a colorless liquid. Although this product is sufficiently pure for use in the next step, the remaining acid may be removed from the anhydride by the following procedure. A slurry of 3.2 g. of phosphorus pentoxide in 31.2 g. of the crude anhydride is stirred at room temperature in a stoppered flask for 18 hours. After the reaction flask has been fitted with a short-path distilling head, it is heated with an oil bath, yielding 0.7 g. of forerun, b.p. 74–81°, followed by 27.9 g. of the pure trifluoromethanesulfonic , b.p. 81–84°.

B. 3-Methyl-2-buten-2-yl triflate. A solution of 2.58 g. (0.0300 mole) of 3-methyl-2-butanone and 2.78 g. (0.0352 mole) of anhydrous pyridine in 10 ml. of anhydrous n-pentane is placed in a dry, 50-ml. Erlenmeyer flask, and the flask is stoppered with a rubber septum. After the solution has been cooled in an acetone–dry ice cooling bath, 9.72 g. (5.80 ml., 0.0395 mole) of trifluoromethanesulfonic anhydride is added with a hypodermic syringe, dropwise and with swirling over 2–3 minutes. The resulting mixture, from which a white solid separates initially, is allowed to warm to room temperature over 22–24 hours. During this period the reaction mixture becomes red in color, and a viscous, red semisolid separates. The supernatant pentane solution is decanted, and the residual viscous semisolid is washed with two 10-ml. portions of pentane. While the combined pentane solutions are stored over anhydrous potassium carbonate, the remaining red semisolid is dissolved in 5 ml. of saturated aqueous sodium bicarbonate and extracted with three 5-ml. portions of pentane. The combined pentane solutions (including the solid potassium carbonate) are washed rapidly (Note 8) with 5 ml. of cold saturated aqueous sodium hydrogen carbonate and dried over anhydrous potassium carbonate. After the orange pentane solution has been concentrated to a volume of approximately 10 ml. with a rotary evaporator, it is transferred to a small distilling apparatus. The remaining pentane is removed by distillation at atmospheric pressure. The residual liquid is fractionally distilled under reduced pressure, yielding 2.94–2.97 g. (45%) of a colorless, liquid fraction containing 3-methyl-2-buten-2-yl triflate and a lesser amount of 3-methyl-1-buten-2-yl triflate, b.p. 58–66° (22 mm.),  n²⁵D 1.3832–1.3898. Fractional distillation of this mixture with a 40-cm. spinning band column separated higher boiling fractions, b.p. 45–47° (12 mm.), that contained 98% of the 3-methyl-2-buten-2-yl triflate as a colorless liquid, n²⁵D 1.3838.