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

Simple and practical synthesis of natural benzofuran derivative eupomatenoid-6 via Horner-Emmons type condensation as the key step is described. The umpolung property of aldehyde derivative, α-aminophosphonate was efficiently employed in this reaction. α-Aminophosphonate of anisaldehyde subjected to Horner-Emmons type condensation with 5-bromo-2-methoxybenzaldehyde to yield the deoxybenzoin, which was further methylated and then underwent tandem demethylation-cyclodehydration to afford the benzofuran scaffold in excellent yield. Finally Suzuki coupling with propenyl boronic acid afforded eupomatenoid-6 with an overall yield of 56.8%