Degenerative xanthate transfer to olefins under visible-light photocatalysis

Abstract

The degenerative transfer of xanthates to olefins is enabled by the iridium-based photocatalyst [Ir{dF(CF3)ppy}2(dtbbpy)](PF6) under blue LED light irradiation. Detailed mechanistic investigations through kinetics and photophysical studies revealed that the process operates under a radical chain mechanism, which is initiated through triplet-sensitization of xanthates by the long-lived triplet state of the iridium-based photocatalyst.

Photochemical generation of acyl and carbamoyl radicals using a nucleophilic organic catalyst: applications and mechanism thereof

“…The xanthyl radical IIIa has been reported to display a characteristic absorption peak with a maximum at 620 nm. 34 Accordingly, when a freshly prepared authentic sample of intermediate Ia was excited with a laser beam centered at 355 nm, we observed the formation of a transient species absorbing at 620 nm (half lifetime = 0.1 ± 0.01 ms), consistent with the characteristic line shape of xanthyl radical IIIa ( Fig. 7d ).…”

Visible Light Mediated Photocatalyst Free C–S Cross Coupling: Domino Synthesis of Thiochromane Derivatives via Photoinduced Electron Transfer

“…9 The redox potential of xanthate is −1.78, and under visible light condition it undergoes excitation through n−π* electronic transition of the CS bond, which marks its enhanced electron donation tendency. 10 Taking a cue from the literature, we contemplated on developing a metal/photocatalyst free strategy that employs inodorous xanthate as a sulfur surrogate as well as catalyst for in situ generation of thiolate anion for the C−S bond formation.…”

“…Very recently, Melchiorre’s group have extensively studied xanthate as nucleophilic organic catalyst for the preparation of various carbon centered radicals using visible light condition followed by Giese addition to different electrophiles (Scheme c) . The redox potential of xanthate is −1.78, and under visible light condition it undergoes excitation through n−π* electronic transition of the CS bond, which marks its enhanced electron donation tendency . Taking a cue from the literature, we contemplated on developing a metal/photocatalyst free strategy that employs inodorous xanthate as a sulfur surrogate as well as catalyst for in situ generation of thiolate anion for the C–S bond formation.…”

Novel antibacterial therapy : mechanical force and light-activation

“…Ultraviolet (UV)-visible light have conventionally been utilized in photochemistry to either directly excite the reaction substrate or photocatalyst in order to induce reactions (e.g., in aryl cross-coupling reactions) [122][123][124] .…”

“…Controlled conjugation or release of biomolecules plays critical roles in various biological applications 153 . Ultraviolet (UV)-visible light has been extensively used in photocatalysis to induce biochemical conjugation reactions [122][123] . Meanwhile, the utilization of UV light is limited due to its toxicity such as DNA damage and protein degradation, and poor penetration depth [154][155] .…”