Sustainable Microwave‐Enhanced Synthesis of 2‐Substituted Benzofurans From o‐Alkynylanisoles in Acidic Deep Eutectic Solvents

The research on alternative media for organic transformations remains a highly demanding topic. In this paper, we describe a sustainable, microwave-enhanced approach to 2-substitued benzofurans starting from substituted o-alkynylanisoles. The method involves the use of an acidic deep eutectic solvent that acts simultaneously as reaction medium and catalyst. The optimized reaction conditions are quite mild (100°C) and the process is complete within 3 h. The reaction setup is simple and does not require an inert atmosphere. Under these conditions, seventeen benzofurans were synthesized in yields of up to 90%. A plausible reaction mechanism has been proposed and supported by headspace GC analyses. To evaluate the sustainability of the process Sheldon's simple environmental factor was also calculated.