A quinonoid naphthopyranone as a model for the synthesis of the pigment xylindein

3-Propyl-3,4,5,10-tetrahydronaphtho [2,3-c] pyran-1,5,10(1H)-trione has been synthesized with a view to determining a satisfactory pathway to its 7,9-dihydroxy-analogue, which it is hoped will ultimately provide a route to the extended quinonoid pigment, xylindein. A key step in the reaction sequence is the photo-rearrangement of 1,4-dimethoxy-trans-3-pent-1-enylnaphthalene-2-carboxylic acid into the related delta-lactone having the required ring system. Subsequent silver(II) oxide oxidative demethylation affords the target quinone