Base-Catalyzed Hydroarsination at Ambient Temperature: Synthesis in Green Solvent

A practical, transition-metal-free hydroarsination protocol using commercially available, air-stable catalytic NaOH in DMSO is described. Hydroarsination has been sorely underdeveloped, and these conditions enable the regioselective anti-Markovnikov addition of diphenylarsine to vinylarenes, Michael acceptors, and alkynes at ambient temperature, affording previously unknown tertiary arsines in good to quantitative yields. Deuterium labeling studies support a nucleophilic mechanism initiated by arsine deprotonation. Because NaOH is not fully soluble in DMSO under the conditions screened, the insoluble component provides water management during the reaction as well as additional base to (re)activate arsine, which explains the high activity relative to reported catalysts. This simple methodology expands access to previously inaccessible substrates and therefore structurally diverse tertiary arsines with a substantial improvement in activity and scope over prior catalysts while reducing cost, simplifying purification, and improving green aspects of the reaction.