Cobalt Single-Atom Catalyst at PPM Level Reduces Sulfonyl Chlorides to Sulfinate Esters

Abstract

The development of green and sustainable synthetic pathways for sulfinate esters is of critical importance to the pharmaceutical and chemical industries. Herein, we present a catalytic strategy that accomplishes this synthesis under mild conditions using an ultra-low catalyst amount (0.01 mol%, 0.42 ppm). The key to this strategy is a cobalt single-atom catalyst (CoSA-N/C), derived from a bimetallic metal-organic framework (MOF) precursor. X-ray absorption fine structure (XAFS) spectroscopy confirmed its Co-N4 coordination structure. This precise atomic dispersion and unique coordination environment are directly responsible for the catalyst's exceptional performance, which achieves a remarkable turnover number (TON) of 6754 and a turnover frequency (TOF) of 1126 h-1 (based on 0.2 mg CoSA-N/C, 2.9×10⁻⁵ mmol Co). Notably, the catalyst and the alcohol reagent can both be easily recovered and reused, highlighting its economic promise. Building on this inherent practicality, integrating the catalysis into a continuous-flow system further amplified its efficiency, which reaction times were shortened, and the TOF increased fourfold. The environmental merits of the overall approach are underscored by green metrics, yielding an EcoScore of 76 and an E-factor of 4.8. Collectively, this atomically precise catalytic platform establishes a powerful and sustainable tool for sulfinate ester synthesis, while also paving the way for broader advancements in sustainable organosulfur chemistry.