Catalyst and Sensitizer‐Free Visible‐Light‐Induced C(sp²)−H Chalcogenation of Arenes/ Heteroarenes with Dichalcogenides

Abstract

A direct selenation of arenes and heteroarenes at room temperature has been accomplished. This protocol was enabled by a visible‐light‐promoted single‐electron‐transfer (SET) pathway without a directing group. An array of arenes and heteroarenes, such as indoles, pyrroles, and functionalized aryl substrates could go through this selenation with high yields and regioselectivity. The salient feature of this protocol is the SET achieved by irradiating one of two organic molecules thereby avoiding a sensitizer to form a radical ion pair.

Recent Developments in Photo‐Catalyzed/Promoted Synthesis of Indoles and Their Functionalization: Reactions and Mechanisms

“…Vijaykumar and co‐workers discovered a visible light‐induced direct regioselective C( sp 2 )‐H chalcogenation of indoles with dichalcogenides under neutral conditions without the addition of catalyst and sensitizer (Scheme 116). [179] The possible mechanism is shown in Scheme 116. Firstly, diphenyl diselenide is converted into excited‐stage intermediate 341 under visible‐light irradiation.…”

“…[178] Vijaykumar and co-workers discovered a visible light-induced direct regioselective C(sp 2 )-H chalcogenation of indoles with dichalcogenides under neutral conditions without the addition of catalyst and sensitizer (Scheme 116). [179] The possible mechanism is shown in Scheme 116. Kumar and co-workers also developed a photocatalyst-/base-/metal-free visible light-induced protocol for the synthesis of 3-organochalcogenyl indoles through the construction of C-chalcogen (S, Se, Te) bond using O 2 as an oxidant (Scheme 117).…”

Visible Light‐Mediated Functionalization of Selenocystine‐Containing Peptides

“…Notably, photocatalyst‐free selenylation of indole can be performed by prolonged irradiation in ethanol [22] or in methanol under flow conditions [23] . Another green method for selenylation of allenes [24] and (hetero)arenes [25] has been established using LiCl as an additive and a household white LED lamp (λ=430–730 nm) as the light source. The abovementioned methods were limited solely to the use of diorganyl diselenides, whereas photocatalyst‐ and additive‐free methods for the synthesis of 3‐selenyl‐, 3‐tellanyl‐, 3‐sulfenyl‐ and 3‐thiocyanoindoles were achieved by employing 26 W CFL bulbs or sunlight, resulting in similar reaction yields [26] .…”

Base‐Promoted Direct Chalcogenylation of 2‐Naphthols

“…Although many useful methods for regioselective sulfanylation of naphthols have been reported, selanylation has been less studied, and these reactions mainly involve electrophilic aromatic substitutions . Additionally, some of them are photoinduced methods, which use expensive, complex molecules as photosensitisers or stoichiometric amounts of mediators …”