Expeditious Synthesis of Natural Benzofuran, Eupomatenoid-6 by Umpolung of α-Aminophosphonates

E-mail: jgjun@hallym.ac.krReceived September 5, 2014, Accepted September 25, 2014Simple and practical synthesis of natural benzofuran derivative eupomatenoid-6 via Horner-Emmons typecondensation as the key step is described. The umpolung property of aldehyde derivative, α-aminophosphonatewas efficiently employed in this reaction. α-Aminophosphonate of anisaldehyde subjected to Horner-Emmonstype condensation with 5-bromo-2-methoxybenzaldehyde to yield the deoxybenzoin, which was furthermethylated and then underwent tandem demethylation-cyclodehydration to afford the benzofuran scaffold inexcellent yield. Finally Suzuki coupling with propenyl boronic acid afforded eupomatenoid-6 with an overallyield of 56.8%.Key Words : α-Aminophosphonate, Kebachnik-Fields reaction, Horner-Emmons type condensation, Suzukicoupling, Eupomatenoid-6IntroductionSubstituted benzofurans are attractive targets of organicsynthesis because of their physiological, pharmacologicaland therapeutic properties.