The synthesis and utility of unprecedented fluorenofurans 7 and oxa-s-indacenones 8 as key intermediates for synthesis of methoxsalen 1 is described, illustrating a novel synthetic approach to furocoumarins.
respectively in good yields (≥70%). Flash vacuum pyrolysis of O-methyl derivatives 9b and 21b at ∼ 500° C/. 1 mm provide furoindacenones 16b and 22b respectively, which in turn are convertible to furocoumarins 1 and 3.