Synthesis of new dibenzofuran derivatives via Diels-Alder reaction of euparin with activated acetylenic esters

An efficient synthesis of novel dibenzofuran derivatives has been achieved via the Diels-Alder reaction of 1-(6-hydroxy-2-isopropeny1-1-benzofuran-y1)-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. (C) 2015 Published by Elsevier Ltd.