Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• group with a less hindered portion is observed. The mechanism revealed the reaction undergoes the homolytic cleavage of the diaryliodonium salt to produce an iodoaryl radical cation, which further reacts with the amine to acquire the corresponding diaryl amines. Moreover, a similar reaction tried with a

• benzyl ester generated rather than the corresponding methyl esters. The reaction was also performed with a 6-membered cyclic diaryliodonium salt, which proceeded successfully and produced the respective iodo-containing arylated product in 59% yield with 76% ee after 24 h. Using the same reaction

• trifluoromethanesulfonate (TMSOTf). This synthesis was conducted in a mixture of 2,2,2-trifluoroethanol (TFE) and dichloromethane [78]. The synthesized naproxen-containing diaryliodonium salt 67 was further used to modify the aromatic ring of naproxen methyl ester 68 (Scheme 27). Various functionalization reactions which

Ortho-ester-substituted diaryliodonium salts enabled regioselective arylocyclization of naphthols toward 3,4-benzocoumarins

• Ke Jiang,
• Cheng Pan,
• Limin Wang,
• Hao-Yang Wang and
• Jianwei Han

Beilstein J. Org. Chem. 2024, 20, 841–851, doi:10.3762/bjoc.20.76

• investigations demonstrated the ability of diaryliodonium salts for selective mono-arylation of 2-naphthols [34]. In this context, we embark on a strategy to modify the neighbouring position of the diaryliodonium salt with an ester group, presenting a novel copper-catalysed regioselective arylocyclization of

• naphthols and substituted phenols. This method represents an efficient approach to access 3,4-benzocoumarin derivatives (Scheme 1c). Results and Discussion To start the study, we used 2-naphthol (1a) and 1.1 equivalents of ortho-methyl formate-substituted diaryliodonium salt 2a as template substrates. The

• diaryliodonium salt 2a. Naphthol 1a forms intermediate B with A after participation with the Cu(II) catalyst. Intermediate B generates C by radical substitution. A final intramolecular transesterification yields the benzocoumarin product 3aa. Conclusion In summary, we have employed ortho-ester-substituted

Synthesis of N-acyl carbazoles, phenoxazines and acridines from cyclic diaryliodonium salts

• Nils Clamor,
• Mattis Damrath,
• Thomas J. Kuczmera,
• Daniel Duvinage and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 12–16, doi:10.3762/bjoc.20.2

• [33][34]. Results and Discussion Initially, we investigated the synthesis of N-acyl carbazole by treatment of diaryliodonium salt 1a with valeramide using Cu(I) catalysts [18]. The results are shown in Table 1. In the first experiments in p-xylene at 120 °C with DMEDA as N,N-ligand, only modest

• lower 25% and 26% yields. Lastly, we synthesized 3f using the standard procedure for iodoliums with more sophisticated benzimidazole-containing diaryliodonium salt, but we only observed a reproducible yield of 8%. The analysis of its solid-state structure showed the desired connectivity [36]. Conclusion

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• authors noted the use of the diaryliodonium salt Ph2IOTf was critical, with no reaction being observed in its absence. In 2020, Li and Shen reported a similar transformation for the synthesis of chloro-containing oxindoles 141 (Scheme 28) [122]. Interestingly, the authors reported the reaction was able to

• operate in the absence of any external oxidants under an inert atmosphere. Although not investigated, Loh’s transformation most likely begins with the generation of an aryl radical from the reduction of the diaryliodonium salt with Fe(II) which subsequently abstracts a hydrogen from CH2Cl2 to generate an

Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

• Andreas Boelke,
• Yulia A. Vlasenko,
• Mekhman S. Yusubov,
• Boris J. Nachtsheim and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223

• cyclic (33) diaryliodonium salt. Pseudocyclic salt 25 was heated to 185 °C and the resulting oily residue was analyzed by GC–MS (Scheme 1a). Besides dearylation to aryl iodide 25a we observed the formation of an N-arylated product 25b in significant amounts. In a similar experiment compound 33 was heated

• diaryliodonium salt 25. TGA/DSC curves for the cyclic triazole 32. The thermal decomposition of (pseudo)cyclic N-heterocycle-stabilized mesityl(aryl)-λ3-iodanes 25 and 33. Supporting Information Supporting Information File 246: Synthetic procedures as well as TGA/DSC curves and NMR spectra for all investigated

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• economy is quite low, since a half of the diaryliodonium salt 87 is lost in the process. Replacing the arene substrate 86 by ketones, and keeping nearly equal reaction conditions, the same authors have achieved an efficient synthesis of 3-(2-oxopropyl)- or pentacyclic isoindolinones 90 or 92 (Scheme 26

• ketones 89 and 91, seem to happen through an N-aryl nitrilium cation intermediate 93, resulting from the reaction between formylbenzonitrile 85 and diaryliodonium salt 87 (Scheme 27). Intramolecular nucleophilic attack of the carbonyl group onto the nitrilium species would furnish cyclic intermediate 94

Metal-free formal synthesis of phenoxazine

• Gabriella Kervefors,
• Antonia Becker,
• Chandan Dey and
• Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

• a high-yielding O-arylation of a phenol with an unsymmetrical diaryliodonium salt to provide an ortho-disubstituted diaryl ether. This species was cyclized to acetylphenoxazine in moderate yield. The overall yield in the three-step sequence is 72% based on recovered diaryl ether. An interesting

• , unusually stable iodine(III) intermediate in the O-arylation was observed by NMR and could be converted to the product upon longer reaction time. Keywords: arylation; cyclization; diaryl ether; diaryliodonium salt; phenol; Introduction Phenoxazine (1) is a tricyclic compound consisting of an oxazine ring

• phenol 6 with unsymmetrical diaryliodonium salt 7a provided the desired diaryl ether 3 in modest yield and limited chemoselectivity (Scheme 5). Competitive N-arylation of the amide moiety [31][32] was not observed. Preliminary attempts to employ the bisiodonium salt 11 in the arylation of 6 were

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• waste. Examples for their atom-economical utilization, in which at least both aryl ligands are transferred, are still rare. A general approach would involve at first a metal-catalysed or metal-free arylation step of a suitable substrate A with the diaryliodonium salt 1 to give monoarylated intermediate

• diaryliodonium salt 1. It is worth to mention, that the AE of 51% (for Ar1 = Ar2 = Ph, X = TfO–, R = Me) is only valid if both dithiocarbamates 7 and 7’ are defined as desired reaction products. If symmetrical diaryliodonium salts are used, as also demonstrated, only one arylation product is formed. The proposed

• reaction mechanism starts with the oxidative addition of the diaryliodonium salt 1 to copper(I) iodide affording the Cu(III) species A, releasing aryl iodide 2. Coordination of the disulfide 6 to the metal centre leads to complex B, followed by the base-induced formation of arylcopper sulfide complex C and

One-pot synthesis of diaryliodonium salts from arenes and aryl iodides with Oxone–sulfuric acid

• Natalia Soldatova,
• Pavel Postnikov,
• Olga Kukurina,
• Viktor V. Zhdankin,
• Akira Yoshimura,
• Thomas Wirth and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 849–855, doi:10.3762/bjoc.14.70

• previously described reaction conditions [37][38], initial optimization studies were performed using iodobenzene and toluene as reactants for the synthesis of diaryliodonium salt 3a (Table 1). A simple mixing of the starting materials with finely ground Oxone and sulfuric acid leads to the formation of a

Synthesis of fluoro-functionalized diaryl-λ³-iodonium salts and their cytotoxicity against human lymphoma U937 cells

• Prajwalita Das,
• Etsuko Tokunaga,
• Hidehiko Akiyama,
• Hiroki Doi,
• Norimichi Saito and
• Norio Shibata

Beilstein J. Org. Chem. 2018, 14, 364–372, doi:10.3762/bjoc.14.24

• arylation reactions in synthetic organic chemistry, but their biological properties are not fully understood. Herein, after initially investigating 18 fluoro-functionalized reagents, we discovered that the ortho-fluoro-functionalized diaryliodonium salt reagents showed remarkable cytotoxicity in vitro

• )phenyl)iodonium exhibited the greatest potency in vitro against U937 cells. Evaluation of the cytotoxicity of selected phenylaryl-λ3-iodonium salts against AGLCL (a normal human B cell line) was also examined. Keywords: biological activity; diaryliodonium salt; fluorine; hypervalent iodine; lymphoma

• SF5-diaryliodonium salts 3p, 4b, 5a and 6a were characterized spectroscopically. The single crystal X-ray structure of 3p was also analysed. The SF5-diaryliodonium salt 3p has a T-shaped geometry at the iodine centre, consistent with the general structure of diaryliodonium salts [33] (Figure 3

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• respective sulfides when it is conducted under inert atmosphere, whereas aerobic conditions selectively lead to the respective sulfoxides. They propose a mechanism where first the diaryliodonium salt is photoreduced by the excited-state of Eosin Y, yielding an aryl radical and Eosin Y radical cation

Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

• Stefan Riedmüller and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2013, 9, 1202–1209, doi:10.3762/bjoc.9.136

• decomposition pathways of the diaryliodonium salt (2-iodobiphenyl, 2,2'-diiodobiphenyl, and 2-(2,5-dimethylphenyl)-2'-iodobiphenyl) [29][30][31]. To further verify these observations, we reacted 1 in the presence of aniline (2a) for three days at elevated temperature without adding a Pd catalyst. Again, after

• reacted 6 with p-fluoroaniline (2f) according to our previously described optimized conditions (Scheme 4). However, 3f was obtained in only 25% yield (Scheme 4), compared to 71% when using the corresponding diaryliodonium salt 1 (Figure 3). Apart from the desired product, we were able to isolate two

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• deficient nature and high dissociation rates that make them excellent leaving groups. Symmetric salts are usually more desirable than asymmetric compounds purely for the reason that this avoids problems that can occur with selectivity in aryl-transfers. If a diaryliodonium salt is asymmetric it is usually