The addition of thiyl radicals to alkenes and alkynes is well known and utilized in organic synthesis, while the corresponding isomerization reactions definitely require the subsequent elimination of thiyl units from the adduct. Some combinations of substrates with well-designed molecular catalysts having steric bulkiness can achieve the elimination reaction, leading to the catalytic cycle closed. However, efficient catalytic The energies for the non-radical process (green trace) were taken from the literature for maleate isomerase catalyzed isomerization with Cys194 as a nucleophile. (b) Molecular orbitals at the thiyl insertion step.