Dioxygen-Triggered Oxidative Radical Reaction: Direct Aerobic Difunctionalization of Terminal Alkynes toward β-Keto Sulfones

An unprecedented dioxygen-triggered oxidative radical process was explored using dioxygen as the solely terminal oxidant, realizing aerobic oxidaitve difunctionalization of terminal alkynes toward β-keto sulfones with high selectivity. Operando IR experiments revealed that pyridine not only acts as a base to successfully surpress ATRA (atom transfer radical addition) process, but also plays a vital role in reducing the activity of sulfinic acids.