Novel PdII-mediated cascade carboxylative annulation to construct benzo[b]furan-3-carboxylic acids

Benzo[b]furan-3-carboxylic acid (2) was generated from 1 by forming three new bonds in one step via a Pd-II-mediated cascade carboxylative annulation. The proposed mechanism was supported by the observation of an unusual acetylation of 1 as a side reaction together with an O-18-labeling study.