HFIP-Assisted Electrochemical Annulation of Enaminones with Phenols for the Selective Synthesis of 7-Aryloxy and 5-Hydroxy Benzofurans.

The electrochemical annulation reactions between enaminones and phenol derivatives have been achieved for the selective synthesis of 7-aryloxy benzofurans and 5-hydroxy benzofurans. With an electron-donating group (EDG), such as alkoxy or amino-functionalized phenols as reaction partners, the 7-aryloxy benzofurans have been furnished via benzofuran annulation and aryl C-H aryloxylation. On the other hand, using hydroquinone as a reaction partner under slightly modified conditions allows the selective synthesis of 5-hydroxy benzofurans. Importantly, the cyclic voltammetry (CV) experiments confirm that hexafluoroisopropanol (HFIP) plays a crucial role in the titled reaction by lowering the oxidation potential of phenol substrates.