THE SYNTHESIS OF SOME PYRANO[2,3-G]CHROMENE-2,7-DIONES AND FURO[2,3-G]CHROMEN-6-ONES

The o-hydroxyformylcoumarin 5b, easily prepared from compound 1, is fu rther transformed to the title coumarin derivatives 7, 10, 19a-c via i ts initial Wittig olefination with ylides 2b, 8, 18a-c respectively. C oumarins 16a,b were also formed by treatment of 5b with compounds 15a, b. The preparation of the interesting furocoumarin derivatives 11, 14, 20b,c as well as of compound 13 is also described.