An efficient synthesis of novel dibenzofuran derivatives has been achieved via the Diels–Alder reaction of
1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone, named euparin, with acetylenic diesters and
propiolates in the presence of triphenylphosphine as a catalyst in toluene. All products were obtained
by recrystallization from ethanol and did not require column chromatography
