NaSH-HCl mediated reduction of sulfoxides into sulfides under organic solvent-free reaction conditions

NaSH·H₂O and 37% aqueous solution of HCl were employed in reduction of sulfoxides to sulfides at room or elevated temperature in the absence of organic reducing agent and solvent-free reaction conditions. Operationally simple transformation took place in the presence of air and in the absence of heavy metals and organic reagents, yielding sodium chloride and sulfur as non-hazardous waste. Heterogeneous reaction conditions proved challenging, particularly in the cases of more hydrophobic substrates, requiring elevated amount of reactants and temperature. Products were isolated by extraction with <i>tert</i>-butyl methyl ether and “filtered” over a short pad of silica gel. Scale-up reaction was demonstrated, including completely solvent-free isolation and purification of the product. A potential reaction course was proposed.

一水合硫氢化钠（NaSH·H₂O）与37%氯化氢水溶液可用于将亚砜还原为硫醚，反应可在室温或升温条件下进行，无需有机还原剂，且采用无溶剂体系。该转化操作简便，可在空气氛围中进行，无需使用重金属与有机试剂，副产物仅为氯化钠与单质硫，均属于无危害废弃物。非均相反应体系存在一定挑战，尤其针对疏水性较强的底物时，需提高反应物用量与反应温度。产物通过甲基叔丁基醚（tert-butyl methyl ether）萃取，并经短硅胶柱过滤分离。本研究验证了该反应的放大可行性，包括完全无溶剂的产物分离与纯化工艺，并提出了可能的反应历程。