Reaction of Organic Sulfides with Singlet Oxygen. A Revised Mechanism

Abstract

On the basis of ab initio calculations we propose a revised mechanism for the reaction of organic sulfides with singlet oxygen, which is more consistent with experimental evidence than previous schemes. In aprotic solvents the reagents initially form a weakly bound peroxysulfoxide, with a small barrier due to entropy. The peroxysulfoxide may decay back to ground state (triplet) oxygen, be trapped by sulfoxides, or rearrange to a S-hydroperoxysulfonium ylide with a barrier of ∼6 kcal/mol. The latter is ∼6 kcal/mol more stable than the peroxysulfoxide, and can be trapped by sulfides or rearrange to a sulfone. In some cases, like five-membered rings or benzylic sulfides, the S-hydroperoxysulfonium ylide may undergo a 1,2-OOH shift to an α-hydroperoxysulfide, which eventually leads to cleavage products. In protic solvents the peroxysulfoxide is rapidly converted to a sulfurane by solvent.

Photooxidation of metal-bound thiolates: reactivity of sulfur containing peroxidic intermediates

“…As previously published by our group, complex 22 reacts with singlet dioxygen to form the corresponding sulfenato complexe [Co(en) 2 …”

“…The reaction of singlet oxygen with organic sulfides proceeds via at least two transient intermediates (1)(2)(3)(4). A large amount of research has focused on the nature of these extremely unstable species, none of which has been directly observed.…”

“…In a seminal paper (1), Liang et al established (2); A cyclic thiadioxirane analogous to the recently observed (6) phosphadioxirane has been ruled out since the barrier of conversion from the persulfoxide to a thiadioxirane would be at least 20 kcal/mol which is incompatible with the experimental observation of the fleeting nature of the persulfoxide (7). The hydroperoxy sulfonium ylide subsequently reacts with starting material to give two equivalents of sulfoxide (usually, this is the major pathway) or intramolecularly collapses to sulfone.…”

Reactive oxygen species (ROS) generation, impacts on tissue oxidation and dietary management of non-communicable diseases: A review

“…The accelerated riboflavin-sensitized destruction of ascorbic acid in the presence of histidine and tyrosine suggesting that the intermediate reaction products of amino acid and 1 O 2 were responsible (Jung et al, 1995 (Kanofsky and Sima, 1991) points to the potential reversibility of O 3 and 1 O 2 from common intermediaries. A potential mechanism can be speculated for cysteine and methionine that alkyl sulfides react with 1 O 2 to form a nucleophilic peroxysulfoxide (RSOO-) (Jensen et al, 1998). Since 1 O 2 is electrophilic, (Min and Boff, 2002), it might easily react with the peroxysulfoxide to form a tetroxysulfoxide RSOOOO-, which could decompose to form ozone and a sulfoxide RSO.…”

“…Since 1 O 2 is electrophilic, (Min and Boff, 2002), it might easily react with the peroxysulfoxide to form a tetroxysulfoxide RSOOOO-, which could decompose to form ozone and a sulfoxide RSO. Notably, sulfoxides are major products of sulfide oxidation (Jensen et al, 1998;Min and Boff, 2002). The sulfoxide can behave as a nucleophile and thus react with 1 O 2 to form RSOOO-, which could decompose to form ozone and regenerate the sulfide.…”