Synthetic studies related to franklinone and acid-catalysed rearrangements of pyronochromanone derivatives

Abstract

Reaction between ββ-dimethylacrylic acid and phloroglucinol in polyphosphoric acid at 100° gave both linear and angular dihydropyronochromanones. Under these conditions the angular isomer can be rearranged to the linear product. Reduction of both products gave dihydropyranochromanones. An attempt to dehydrogenate tetrahydrofranklinone to franklinone was unsuccessful and gave a bromopyranochromene.