Monoalkylation of dihydroxycoumarins via Mitsunobu dehydroalkylation under high intensity ultrasound. The synthesis of ferujol

Monoalkylation of natural dihydroxycoumarins was carried out by Mitsunobu dehydroalkylation under sonochemical conditions. Aesculetin (6,7-dihydroxycoumarin) was selectively alkylated in good yield with prenyl alcohols at position 7, as clearly shown by NOESY experiments; though less selectively, position 7 was also the most reactive in daphnetin (7,8-dihydroxycoumarin). The synthesis of the phytoestrogen ferujol is also reported for the first time.