REACTION OF BENZO-4-PYRONES WITH DIMETHYLSULPHOXONIUM METHYLIDE

The reaction of benzo-4-pyrones with dimethylsulphoxonium methylide gives three types of products, 2,3-dihydro-2,3-methanobenzo-4-pyrones(V),2- vinylcoumaran-3-ones (VI), and 1-(2-hydroxyaryl)butane-1,4-diones (VII). The 2,3-dihydro-2,3-methanobenzo-4-pyrones (V) are readily hydrolysed to the butane-1,4-diones (VII), and this reaction may occur during the isolation of the latter products. The structural relation between these products is discussed in terms of reaction mechanism, and the effects of substituents upon product ratios are also considered.