Biomimetic Reduction of Sulfuric Acid

Sulfuric acid and sodium sulfate were readily reduced to elemental sulfur and hydrogen sulfide upon treatment with a mixture of either one of polyphosphoric acid derivatives, PPE, PPA, and P4O10, which can form a mixed anhydride having –P–O–S– linkage, and iodide or thiol. Sulfur dioxide, which is undoubtedly one of important intermediates, was trapped by p-tolyllithium to afford p-toluenesulfinic acid which was converted to p-tolyl methyl sulfone upon treatment with methyl iodide, though the yield was low. Sulfur trioxide which has been postulated as the key intermediate in the biological reduction of inorganic sulfate, was also trapped by mesitylene to give mesitylenesulfonic acid in a high yield. The reduction of sulfate to elemental sulfur and hydrogen sulfide is considered to proceed through the course which resembles the biological reaction path involved in the assimilatory metabolism of inorganic sulfate in microorganisms and plants.