Synthesis of Benzofurans from Ketones and 1,4‐Benzoquinones

Abstract Benzofuran derivatives can be synthesized through the sequential Michael addition and cyclization of 1,3‐dicarbonyl compounds with 1,4‐benzoquinones. However, ketones are rarely used in this reaction because of their low nucleophilicities. In this study, this problem was solved by utilizing triethyl orthoformate, which enabled the formation of a vinyl ethyl ether as an additive. As a result, the nucleophilicity of ketones increased. Many important 5‐hydroxybenzofuran derivatives, which were not readily available by synthesis in the past, were also prepared via these newly established reactions. magnified image