Operationally Simple, Efficient, and Diastereoselective Synthesis of cis-2,6-Disubstituted-4-Methylene Tetrahydropyrans Catalyzed by Triflic Acid

A highly efficient (0.01 mol % of TfOH), operationally simple (room temperature, inexpensive, and commercially available catalyst), and diastereoselective (up to >98% de) method for Brønsted acid-catalyzed reaction of enol ethers to form cis-2,6-disubstituted tetrahydropyrans is disclosed.