Benzopyrans. Part 30. Synthesis of substituted xanthones from 3-acyl-2-methyl-1-benzopyran-4-ones

Article abstract of DOI:10.1016/S0040-4020(01)89924-5

The xanthone 8 results from the base catalysed self-condensation of the chromone 1. The chromone 2 gives the xanthones 9 and 11 with sodium and DMF-POCl₃ respectively, phenol 14 with NaOMe, and the pyran 22 with 2-thiomethylchromone 6. The enamine 16 on Vilsmeier-Haak reaction affords the chloroxanthone 12. The pyran 15, isolated as a byproduct from the reaction of ω-acetyl-2-hydroxyacetophenone with HC(OEt)₃-Ac₂O, affords the xanthone 13 by refluxing with NaOMe in MeOH.