Metal-free Intermolecular Hydrophenoxylation of Aryl Alkynes

Base-mediated anti-Markovnikov additions of phenols onto terminal alkynes have been achieved. This paper presents insights into the role of DMSO in superbase-mediated chemo-, regio-, and stereoselective nucleophilic addition reactions of phenols onto aryl alkynes. Deuterium-labeling experiments uncover that the source of styryl protons in the products comes from the DMSO, not from the substrate (nucleophile) nor from the water workup. Competitive nucleophilic additions and the mechanistic pathway was corroborated by control experiments and computational calculations.