Synthesis of 5‐Hydroxy‐4‐Methoxy‐2‐Methylpyrylium Trifluoromethanesulfonate from Kojic Acid

Abstract

Oxidopyrylium ylides are versatile and reactive species that have been used widely in total synthesis, particularly due to their ability to undergo complexity‐forming [5+2] cycloaddition reactions. Group transfer strategies have been generally limited to intramolecular cycloaddition reactions, however, likely due to the short lifetime of the active ylide. However, in 1992 Wender and Mascarenas found that this limitation can be overcome through the use of methyl triflate based pre‐ylide salt. This article describes the procedure for synthesis of 5‐Hydroxy‐4‐methoxy‐2‐methylpyrylium trifluoromethanesulfonate from Kojic acid. It presents some of the important points to be considered, the conditions that need to be maintained, characterization data, and the reagents required, as well as the techniques used and the equipment setup that are vital to carrying out the process. The article also describes the hazards associated with working with chemicals and the ways to deal with these hazards.