Electrochemical borylation of carboxylic acids

Abstract

Significance Boronic acids are one of the most useful functional groups in organic chemistry and can be used as intermediates in synthesis or as key motifs in medicines. This work describes an extremely simple and economical way to use electrochemistry to convert carboxylic acids, through the intermediacy of redox-active esters, to boronic acids. The scope of this reaction is broad, the mechanism has been thoroughly studied, and it can be easily scaled up. Finally, application to the synthesis of a complex polycyclopropane natural product is demonstrated. A simple electrochemically mediated method for the conversion of alkyl carboxylic acids to their borylated congeners is presented. This protocol features an undivided cell setup with inexpensive carbon-based electrodes and exhibits a broad substrate scope and scalability in both flow and batch reactors. The use of this method in challenging contexts is exemplified with a modular formal synthesis of jawsamycin, a natural product harboring five cyclopropane rings.