Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

Synthesis and reactivity of azole-based iodazinium salts

• Thomas J. Kuczmera,
• Annalena Dietz,
• Andreas Boelke and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 317–324, doi:10.3762/bjoc.19.27

• protocol that allowed us to synthesize these novel cyclic iodonium salts in their mono- and dicationic forms, we gained in-depth structural information through single-crystal analysis and demonstrated the ring opening of the heterocycle-bridged iodonium species. For an exclusive set of dicationic

• imidazoiodaziniums, we show highly delicate post-oxidation functionalizations retaining the hypervalent iodine center. Keywords: building block; heterocycles; hypervalent compounds; iodonium salts; one-pot synthesis; Introduction The chemistry of hypervalent iodine compounds, in particular aryl-λ3-iodanes, is

• potential in organic synthesis and catalysis, their structural variation is still limited. In particular, heteroarene-bridged cyclic iodonium salts are rare. Examples include the benzisoxazole-containing iodonium salt 1 described by Lisichkina and Tolstaya (Figure 1) [24][25]. Our group is interested in the

Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• activation/annulation cascade of readily available enaminones with iodonium ylides towards the convenient synthesis of isocoumarins. This coupling system proceeds in useful chemical yields (up to 93%) via a cascade C–H activation, Rh-carbenoid migratory insertion and acid-promoted intramolecular annulation

• . The success of gram-scale reaction and diverse functionalization of isocoumarins demonstrated the synthetic utility of this protocol. Keywords: C–H activation; enaminone; iodonium ylide; isocoumarin; rhodium catalysis; Introduction Isocoumarins are an important structural motif in many naturally

• ]. Compared with highly sensitive diazo compounds, iodonium ylides are known to show ready availability and good stability [29][30]. Our group has recently demonstrated that iodonium ylides can be used as carbene precursors in the Rh-catalyzed [4 + 2] cyclization of pyrazolidinones [31]. During the

Two-step continuous-flow synthesis of 6-membered cyclic iodonium salts via anodic oxidation

• Julian Spils,
• Thomas Wirth and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 27–32, doi:10.3762/bjoc.19.2

• Friedel–Crafts alkylation followed by an anodic oxidative cyclization yielded a defined set of cyclic iodonium salts in a highly substrate-dependent yield. Keywords: electrochemistry; flow chemistry; hypervalent compounds; iodine; oxidation; Introduction Hypervalent iodine compounds (HVI) are well

One-pot synthesis of 2-arylated and 2-alkylated benzoxazoles and benzimidazoles based on triphenylbismuth dichloride-promoted desulfurization of thioamides

• Arisu Koyanagi,
• Yuki Murata,
• Shiori Hayakawa,
• Mio Matsumura and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 1479–1487, doi:10.3762/bjoc.18.155

• cyclopropanes with arenes [29]. They have also been used in Pd-catalyzed cross-coupling reactions to react with hypervalent iodonium salts, organostananes, and vinyl epoxides [30][31][32]. Moreover, there are reports of them serving as oxidizing agents for alcohols [33]. Two papers have recently reported

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• ). However, an iodonium ion 6 was formed as a key intermediate in I2-mediated aza-annulations. Subsequently, the iodonium ion 6 proceeds through a 6-endo-dig cyclization to form the 5-iodopyridine 3. On the other side, the iodonium ion 6 may undergo 5-exo-dig cyclization to yield the 2-acylpyrrole 4

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• abilities were found for some reported dyes when used in combination with iodonium salt and amine. Markedly, photothermal effects with a huge heater behavior were also observed for different NIR dye structures. Interestingly, the synthesis of interpenetrating polymer networks (IPNs, e.g., for the

• ) to generate initiating radicals. In this work, a large series of 17 NIR dyes mainly based on a well-established cyanine scaffold is proposed (Scheme 1). Markedly, eleven of them were never synthesized before. These NIR dyes are studied in three-component systems in combination with an iodonium salt

• combination with an amine and an iodonium salt, iod, for the free radical polymerization of a benchmark acrylate monomer and compared to a reference initiating system based on IR 813 (Scheme 2) [7]. As the different dyes presented above exhibit good absorption properties at 785 nm, the photoinitiating

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• 129b via double iodonium-induced electrophilic cyclization. The terphenyl 130 was converted to the diiododibenzo[a,j]anthracene derivative 132 in two steps comprising cyclization and further treatment of intermediate 131 with sulfuric acid [64]. Watanabe and co-workers investigated the oxidative

• . AuCl-catalyzed double cyclization of diiodoethynylterphenyl compounds. Iodonium-induced electrophilic cyclization of terphenyl derivatives. Oxidative photocyclization of 1,3-distyrylbenzene derivatives. Oxidative cyclization of 2,3-diphenylnaphthalenes. Suzuki-Miyaura/isomerization/ring closing

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom

• Giovanna Zanella,
• Martina Petrović,
• Dina Scarpi,
• Ernesto G. Occhiato and
• Enrique Gómez-Bengoa

Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255

• acid, as previously reported [45]. In the next step, the electrophilic addition of iodine monochloride to the double bond of the enesulfonamide 10, followed by a nucleophilic attack of methanol on the formed iodonium ion afforded the α-methoxy-β-iodopiperidine 11 as a single stereoisomer (91% yield

Copper-based fluorinated reagents for the synthesis of CF₂R-containing molecules (R ≠ F)

• Louise Ruyet and
• Tatiana Besset

Beilstein J. Org. Chem. 2020, 16, 1051–1065, doi:10.3762/bjoc.16.92

• reactivity of the complex was then studied in stoichiometric reactions with aryl iodides and iodonium salts. The difluoromethylation reaction was smoothly carried out at 90 °C with electron-rich and electron-poor aryl iodides. However, the reaction was more efficient with electron-poor aryl iodides (Scheme 1

Copper-catalyzed O-alkenylation of phosphonates

• Nuria Vázquez-Galiñanes,
• Mariña Andón-Rodríguez,
• Patricia Gómez-Roibás and
• Martín Fañanás-Mastral

Beilstein J. Org. Chem. 2020, 16, 611–615, doi:10.3762/bjoc.16.56

• /bjoc.16.56 Abstract Copper catalysis allows the direct oxygen alkenylation of dialkyl phosphonates with alkenyl(aryl)iodonium salts with selective transfer of the alkenyl group. This novel methodology proceeds with a wide range of phosphonates under mild conditions and gives straightforward access to

• (alkenyl)iodonium salts, which are air- and moisture-stable, nontoxic and easy to prepare compounds, have become efficient reagents for mild and selective arylation and alkenylation reactions in organic synthesis [16][17][18]. In particular, the use of these hypervalent iodine reagents in copper catalysis

• copper catalyst on an alkenyl(aryl)iodonium salt [33][34] would generate an alkenyl–copper(III) species which might undergo nucleophilic attack of the Lewis-basic oxygen of a dialkyl phosphonate. The resulting phosphonium-like intermediate would evolve by Arbuzov-type substitution of one of the alkyl

Copper-catalyzed remote C–H arylation of polycyclic aromatic hydrocarbons (PAHs)

• Anping Luo,
• Min Zhang,
• Zhangyi Fu,
• Jingbo Lan,
• Di Wu and
• Jingsong You

Beilstein J. Org. Chem. 2020, 16, 530–536, doi:10.3762/bjoc.16.49

• )iodonium triflate (2a, for detailed optimization, see Table S1, Supporting Information File 1). Initially, the reaction was performed in 1,2-dichloroethane (DCE, 1 mL) at 80 °C for 24 h in the presence of Cu(OTf)2 (10 mol %) as a catalyst. The direct C7–H arylation product N-(tert-butyl)-7-phenyl-1

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• , and no significant selectivity was observed when nonsymmetrical iodonium salts were reacted under the optimized reaction conditions. Later in 2015, Greaney and co-workers described the copper-photocatalyzed azidation of styrene olefins and the concomitant introduction of a nucleophile (Scheme 9) [26

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• imaging applications. This would definitively decrease the efficiency of electron back transfer. Nowadays, typical electron acceptors (AC) applied in such systems related to either iodonium salts or triazines also possess a high capability of electron back transfer resulting in a decrease of the overall

• often no reaction between a cationic sensitizer and an electron acceptor; i.e. an iodonium salt [5]. However, the use of stronger emitting LEDs resulted sometimes in successful PET [67]. Particularly, light sources with low emission intensity arose these issues. This supports the idea that the system

• the outer sphere coordinates (λo) while geometric changes of the starting materials responsible tune inner-sphere coordinates λi (λ = λo + λi) [72]. Many NIR sensitive systems possess an internal activation barrier although ΔGet < 0 using either the positively charged iodonium compound 88 (Ered

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• nitriles [21], carbonyl or imine species [22], iodonium or diazonium salts [23], or halide species [24]. The formation of radicals from halide species by photoredox catalysis has been widely studied. It has been applied as a mild method for the dehalogenation of several compounds [25][26][27]. In the light

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• resulted in the generation of 10 (Figure 1d). Changes in the resonances for the phenyl protons, H-8, H-9, and H-10, if any, were indiscernible. To increase the lifetime of the intermediate 9 so that more detailed analyses could be performed, the iodonium source was changed from I2 to ICl (Figure 1c). The

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• ) [119]. In this reaction, iodine promoted the formation of iodo-intermediate 98 with a carbonyl compound that underwent nucleophilic substitution with 2-AP 3. CuO played multiple roles in this reaction. Firstly it acts as an oxidizing agent to convert molecular iodine to the reactive iodonium ion (I

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• -one (4S,5S)-20 after reduction of the carbon–iodine bond formed in the primary products of cyclization (via iodonium ion 22). Hydrogenolytic debenzylation preceded oxidation of the hydroxymethyl group to afford diester (4R,5S)-21 which after hydrolysis gave (2R,3S)-2 as the hydrochloride (Scheme 5

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• (TMS)3SiH), amines such as ethyl 4-(dimethylamino)benzoate (abbreviated EDB) or carbazole derivatives such as 9-vinylcarbazole (NVK) are presented. As oxidizing agent, it is possible to use a iodonium salt such as diphenyliodonium (Ph2I+). With these additives, three systems involving catalytic cycles

• triplet excited state through metal to ligand charge transfer (Scheme 3, reaction 1). As described in Table 2, the irradiation must be around 450 nm. Thus, as the triplet excited state is long enough and thanks to the values of oxidation potentials, a single electron transfer (SET) to the iodonium salt

• absorption and redox properties through well selected ligands [52]. This Ir-based complex reacts in the photoredox catalytical cycle with iodonium salt and (TMS)3SiH as the Ru-based complex in reactions 1, 2 and 3. Moreover, Iridium complexes can be interesting for applications in ring-opening

Determining the predominant tautomeric structure of iodine-based group-transfer reagents by ¹⁷O NMR spectroscopy

• Nico Santschi,
• Cody Ross Pitts,
• Benson J. Jelier and
• René Verel

Beilstein J. Org. Chem. 2018, 14, 2289–2294, doi:10.3762/bjoc.14.203

• HCl compound 4a afforded an isolable iodonium-type structure [20]. Although this activation can be conveniently followed by 19F NMR spectroscopy with 4a resonating at −40.1 ppm and the fully protonated “iodonium” congener 4c at −20 ppm [1], this technique provides no indication on how to best

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• hypervalent iodine-mediated reactions to achieve the intermolecular oxycarbonylation [79], azidocarbonylation [80] and fluorocarbonylation [81] of alkenes. Mechanistic studies showed that PhI(OAc)2 is activated by the aid of BF3·OEt2 and then reacts with an alkene to form a three-membered iodonium ion

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• iodonium diacetate 132 in 2,2,2-trifluoroethanol/DCM at −10 °C (Scheme 51). Additionally, the synthesized functionalized spirodienone 140 was used as precursor for the synthesis of (+)-plicamine (141). In 2002, Quideau and co-workers [131] developed the synthesis of marine sesquiterpenoid (+)-puupehenone

DFT calculations on the mechanism of copper-catalysed tandem arylation–cyclisation reactions of alkynes and diaryliodonium salts

• Tamás Károly Stenczel,
• Ádám Sinai,
• Zoltán Novák and
• András Stirling

Beilstein J. Org. Chem. 2018, 14, 1743–1749, doi:10.3762/bjoc.14.148

• the basis of the mechanism the origin of the stereoselectivity is ascribed to the interaction of the Cu ion with the oxazoline oxygen driving the ring-closure step selectively. Keywords: catalysis; DFT calculation; iodonium salts; reaction mechanism; tandem arylation–cyclisation; Introduction

• Recently a very efficient synthetic strategy has been developed where diaryl iodonium salt 1 [1][2][3][4][5][6][7][8] and copper(I) catalyst 2 are employed together to produce in situ Ar–Cu(III) species 3 for the carbofunctionalisation of appropriate substrates 4 [9][10][11][12][13][14][15][16][17][18][19