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.

Dual‐Responsive Photocatalytic Polymer Nanogels

“…Previously,asimilar reaction was photocatalysed using Mn-(CO) 5 Br;h owever,t he disulfide bridge formation was performed in organic media (cyclohexane or benzene). [16] In ap ure aqueous solution, 1-octanethiol is converted to 1,2dioctyldisulfane and dioctylsulfane by the dual-responsive photocatalytic nanogels at room temperature.F urthermore, this is the first example of disulfide bridge formation utilising ap ure organic photocatalytic system, with over 88 %o fthe thiol groups converted after 20 h ( Table 1, Figures S14 and S15). Conversely,a te levated temperature only 10 %o ft he thiol was converted ( Figure S16).…”

Dual‐Responsive Photocatalytic Polymer Nanogels

“…[16] In ap ure aqueous solution, 1-octanethiol is converted to 1,2dioctyldisulfane and dioctylsulfane by the dual-responsive photocatalytic nanogels at room temperature.F urthermore, this is the first example of disulfide bridge formation utilising ap ure organic photocatalytic system, with over 88 %o fthe thiol groups converted after 20 h ( Table 1, Figures S14 and S15). Theformation of disulfide bridges within cells is one of the most common post-translational modifications of peptides.T om imic this,t he disulfide bridges were formed between molecules of am odel compound, 1-octanethiol.…”

Electrocatalytic proton reduction catalyzed by a dimanganese disulfide carbonyl complex containing a redox-active internal disulfide bond

“…Our group has shown that thiols could be transformed into disulfides and H 2 using Mn(CO) 5 Br or CpMn(CO) 3 under UV-visible light. 9,10 Since enzymes such as glutathione reductase and cysteine reductase can easily reduce the respective disulfides into thiols using proton sources, combining the features of the manganese complexes and the enzymes into one may convert H + into H 2 without sacrificing thiols in the process through the reversible dissociation and formation of the S-S and S-H bonds.…”