A versatile three-step procedure to annulate a γ-pyrone onto a methylene ketone was developed involving (i) aldol reaction with a dithiolane-protected β-ketoaldehyde,(ii) oxidation of the aldol adduct to a β-diketone, and (iii) treatment of the resulting dithiolane- protected 1, 3, 5-trione with 2-iodoxybenzoic acid (IBX) and trifluoromethanesulfonic acid (triflic acid; TfOH) in acetonitrile at ambient temperature to give the corresponding γ- ...
