Thiyl Radicals: From Simple Radical Additions to Asymmetric Catalysis

Abstract

asymmetric catalysis · enantioselectivity · radicals · synthetic methods · thiols Radicals derived from thiols, often termed as thiyl radicals,

Regio- and Stereoselective Photoredox-Catalyzed Atom Transfer Radical Addition of Thiosulfonates to Aryl Alkynes

“…Photocatalytic cycle begins with oxidative quenching of the excited-state eosin Y* by thiosulfonates 2a to yield the thiyl radical I and Ts anion II . The thiyl radical I is added to phenylacetylene to afford the α-alkenyl carbon radical ( III ), which is then single-electron oxidized by eosin Y • + to deliver the benzyl alkenyl cation IV , and regenerate the ground-state Eosin Y to close up the photocatalytic cycle at the same time. Finally, the target product 3aa was produced from the nucleophilic attack of Ts anion ( II ) to alkenyl cation III .…”

Expanding the Repertoire of Molecular Linkages to Silicon: Si–S, Si–Se, and Si–Te Bonds

“…The third route to formation of Si· is removal of the silicon-bound H· by a chalcogenyl radical, shown in Scheme c. ,, The thiyl, selenyl, and telluryl radicals would result from homolysis of the weak S–S, Se–Se, or Te–Te bond, which have bond dissociation energies of 53–57, ∼40, and ∼30–35 kcal/mol, respectively, under these high-temperature conditions (Scheme d) . Thiyl and selenyl radicals are known radical propagators, and presumably telluryl radicals would play a similar role, plucking hydrogen atoms from the silicon surface to produce silyl surface radicals, particularly under high concentrations of reagents. − …”

Thiol- and Disulfide-Based Stimulus-Responsive Soft Materials and Self-Assembling Systems

“…Alkanethiols and thiophenols have homolytic S-H bond dissociation energies of ca. 87 and 79 kcal/mol, respectively [ 21 ]. Disulfides generally have lower homolytic S-S bond dissociation energies, ranging from 50-65 kcal/mol [ 21 ].…”

“…87 and 79 kcal/mol, respectively [ 21 ]. Disulfides generally have lower homolytic S-S bond dissociation energies, ranging from 50-65 kcal/mol [ 21 ]. Aryl thiols, such as thiophenol, generally have the lowest homolytic S-H bond dissociation energies, especially when an electron donating aryl substituent is present at the para position [ 22 ].…”