Visible-Light Photoredox in Homolytic Aromatic Substitution: Direct Arylation of Arenes with Aryl Halides

Abstract

Direct arylation of unactivated arenes or heteroarenes with aryl halides could be carried out in the presence of potassium tert-butoxide and dimethyl sulfoxide under visible-light irradiation. Ir(ppy)3 was found to be an effective photoredox catalyst for this reaction. The reactions of aryl iodides occurred at room temperature. Elevated temperature was required for aryl bromides. Homolytic aromatic substitution was proposed to be the operative reaction pathway.

Synthesis of 6‐Alkylated Phenanthridine Derivatives Using Photoredox Neutral Somophilic Isocyanide Insertion

“…[7][8][9][10] The radical 5 adds to 1 to produce the imidoyl radical intermediate 6, which undergoes intramolecular homolytic aromatic substitution to give the radical intermediate 7. [14] The 3 ].…”

“…The photocatalysts B-D were also tested, but none of them gave better results (entries [6][7][8]. The base did not affect this transformation significantly and other bases, such as K 2 CO 3 , NaHCO 3 , and K 2 HPO 4 also gave good yields of the isolated products (entries [9][10][11]. Control experiments verified the necessity of the base, irradiation, and photocatalyst (entries [12][13][14].…”

“…While the palladium-catalyzed isocyanide insertions often require high reaction temperatures and have the tendency to undergo multiple consecutive insertions, [5] the use of isocyanides as somophiles for insertion reactions holds promise for practical synthetic applications under mild reaction conditions. [6] As a convenient approach to generate somophiles, photoredox catalysis, [7] which usually introduces alkenes, [8] alkynes, [9] and aromatic rings [10] as radical acceptors, has been widely used in the synthetic community to construct C À C bonds since 2008. [11] However, none of the reported work has employed photoredox catalysis to initiate isocyanide insertion.…”

Graphitic Carbon Nitride Polymer as a Recyclable Photoredox Catalyst for Fluoroalkylation of Arenes

“…Through the usage of cheap, metal-free and recyclable mesoporous graphitic carbon nitride (mpg-CN) it was possible to fluoroalkylate various arenes by the reductive activation of sulfonyl chlorides with visible light. Thus, we were able to demonstrate the robustness and versatility of mpg-CN as a photoredox catalyst beyond water splitting and the activation of oxygen.Using visible light for photoredox catalysis in organic synthesis has aroused great interest in the last couple of years.[1] In particular, light sensitizers like Ru(bpy) 3 2 + , [2] Ir III complexes, [3] or Eosin Y [4] are often employed to initiate organic reactions.However, the homogeneous nature of these dyes makes their separation from the product as well as their recycling difficult. This is where heterogeneous catalysts show major advantages.…”

“…[1] In particular, light sensitizers like Ru(bpy) 3 2 + , [2] Ir III complexes, [3] or Eosin Y [4] are often employed to initiate organic reactions.…”