Naphthopyranone synthesis via the tandem Michael–Dieckmann reaction of ortho-toluates with 5,6-dihydropyran-2-ones

The tandem Michael–Dieckmann reaction between a series of ortho-toluates and the α,β-unsaturated lactone 25 is described. The tandem reaction delivers substituted naphthopyranones in moderate (20–49%) yields, whilst limitations in the tolerance of this reaction for different substituents on the ortho-toluate are identified.