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.