Photocatalytic transformation of organic and water-soluble thiols into disulfides and hydrogen under aerobic conditions using Mn(CO)5Br

Abstract

The photolysis of Mn(CO)5Br with thiols under aerobic conditions at room temperature produces the corresponding disulfides in high yields, accompanied by the evolution of hydrogen as the only other product. This transformation is a greener route toward the synthesis of disulfides and exhibits 100% atom economy. The catalytic system possesses high chemoselectivity, as evidenced by high disulfide yields even in the presence of numerous functional groups. A mechanism has been proposed to involve free radical species and is based on fac-Mn(CO)3(RSH)2Br being an important catalytic intermediate. Mn(CO)5Br is also able to catalyze the conversion of naturally occurring water-soluble thiols such as cysteine and glutathione. Coupled with suitable enzymes that regenerate thiols from disulfides using proton sources, it is possible to envisage a combined catalytic cycle that is able to reduce protons to hydrogen efficiently. © 2011 American Chemical Society.