Visible Light-Driven Azidation/Difunctionalization of Vinyl Arenes with Azidobenziodoxole under Copper Catalysis

Abstract

Visible light-driven azidation of vinyl arenes with azidobenziodoxole as the azidating agent was investigated in acetonitrile by using Cu­(I)­(phenanthroline)2 complex [Cu­(dap)2]­PF6 as photocatalyst. The reactions generated three types of difunctionalization products, which correspond to reaction patterns of amido-azidation, benzoyloxy-azidation, and diazidation. The electronic nature of the aryl group attached to the olefin moiety was found to play a crucial role in determining the reaction consequence: when the aryl group was electron-rich, the reactions afforded benzoyloxy-azidation products exclusively; for highly electron-deficient vinyl arenes, by contrast, diazidation products were generated in moderate yields. When the aryl group was moderately electron-rich or electron-deficient, on the other hand, a three-component reaction involving acetonitrile as well as azidobenziodoxole took place to give predominantly amido-azidation products. A plausible mechanism is proposed based on the mechanistic studies to rationalize these results. The reactions of electronically less biased vinyl arenes probably proceed via a redox catalysis pathway, while the electron-rich alkenes are believed to be converted through a radical chain process. The present reactions may be of synthetic usefulness as they provide a new means for the amido-azidation of vinyl arenes.

Recent Synthetic Applications of the Hypervalent Iodine(III) Reagents in Visible-Light-Induced Photoredox Catalysis

“…In 2019, the group of Yu has investigated the visible-light-driven azidation of vinyl arenes with Zhdankin reagent as azidating agent in acetonitrile by using [Cu(dap) 2 ]PF 6 as photocatalyst (Wu et al, 2019 ) ( Figure 4E ). It was found that the electronic nature of the aryl group attached to the olefin moiety plays a profound effect on the reaction consequence: when the aryl group was less electronically biased, amido-azidation products were obtained as major products through a three-component reaction involving the solvent acetonitrile as well as Zhdankin reagent.…”

Construction of C-N Bond via Visible-Light-Mediated Difunctionalization of Alkenes

“…Electron-withdrawing and electron-donating group of alkene and cyanopyridine react smoothly to give the product (26). According to the proposed mechanism, irradiation of Ir(ppy) 2 (dtbbpy)PF 6 produce an excited state Ir* which would capture a single-electron from azide to generate the azido radical intermediate (A) and reducing photocatalyst Ir II Recently, Guo et al in 2021 demonstrated a photocatalytic 1,2-diamination of 1,3-dienes (27) in the presence of N-aminopyridinium and TMSNCS to affords 1,2aminoisothiocyanation products (28) in high chemo-and regio-selective manner with broad substrate scope and good functional group tolerance (Figure 18) [22]. According to the proposed mechanism (Figure 18 An elegant method for the synthesis of β-sulfonyl amides ( 30) is reported by Zong et al in 2019 through an acid promoted photochemical reaction of styrenes (29), aryldiazonium tetrafluoroborates, sulfur dioxide, nitriles, and water (Figure 19) [23].…”

“…Wu et al in 2019 depicted (Figure 23) a visible-light-mediated Cu-catalyzed difunctionalization of alkene (37) to give azidation product (38) [27]. Here the azidobenziodoxole acts as an azidating agent in the presence of acetonitrile and [Cu(dap) 2 ]PF 6 complex as the photocatalyst.…”

Iron‐Catalyzed Radical Asymmetric Aminoazidation and Diazidation of Styrenes

“…In spite of the advances in related non‐asymmetric reactions, [21a–k, 23] enantioselective aminoazidation and diazidation are underdeveloped. There is only one example of a successful enantioselective aminoazidation, an intra/ intermolecular aminoazidation leading to structurally diverse substituted piperidines (Scheme 1 c).…”