Development of a Robust Protocol for the Synthesis of 6‑Hydroxybenzofuran-3-carboxylic Acid

Benzofuran scaffolds are fundamental moieties found in a variety of biologically active natural products and synthetic drugs. In the course of one of our development programs, we needed to develop a practical and cost-effective manufacturing approach to such a benzofuran scaffold. Here we report a highly robust four-step, one-pot process that provides access to a 6-hydroxybenzofuran-3-carboxylic acid structure. An 1H NMR monitoring study allowed a better understanding of the overall sequence of events and the nature of the detected intermediates. After six steps, including the optimized tandem process, the desired hydroxylated benzofuran was obtained in 40% yield with a purity above 99%.