A concise and efficient synthesis of benzimidazo[1,2-c]quinazolines through CuI-catalyzed intramolecular N-arylations

• Xinlong Pang,
• Chao Chen,
• Ming Li and
• Chanjuan Xi

Beilstein J. Org. Chem. 2015, 11, 2365–2369, doi:10.3762/bjoc.11.258

• : benzimidazo[1,2-c]quinazoline; (bromophenyl)iodonium salt; copper catalyst; o-cyanoaniline; quinazolin-4(3H)-imine; Ullmann N-arylation; Introduction Nitrogen-containing heterocycles are ubiquitous backbones in natural products, medicine and organic materials. In addition, they are also important ligands for

• diaryliodonium salts 2 to produce quinazolin-4(3H)-imine derivatives 3 with Cu(OTf)2 as the catalyst [13]. Encouraged by this finding, we initially attempted the reaction of o-cyanoaniline (1a) with di-(o-bromophenyl)iodonium salt 2. The reaction of 2 equiv of o-cyanoaniline (1a) with 2 in DCE at 110 °C for 6 h

• nitriles. The reaction of o-cyanoaniline (1a), benzonitrile (1g) and di-(o-bromophenyl)iodonium salt 2 in the presence of Cu(OTf)2 gave the desired imine 3g together with imine 3a. After isolation of 3g it was further treated with 10 mol % of CuI in DMSO for 50 min to give product 4g in quantitative yield

Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• excess of KI) [14]. The side-product in the iodination of 3 was bis(pyridine)iodonium tetrafluoroborate, which can be easily isolated from the reaction mixture by precipitation upon addition of diethyl ether. This iodonium salt was first synthetized by Barluenga [85] and later used for mild iodination of

Switching the reaction pathways of electrochemically generated β-haloalkoxysulfonium ions – synthesis of halohydrins and epoxides

• Akihiro Shimizu,
• Ryutaro Hayashi,
• Yosuke Ashikari,
• Toshiki Nokami and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2015, 11, 242–248, doi:10.3762/bjoc.11.27

• . Keywords: DMSO; electrosynthesis; epoxides; halohydrins; halogen cations; Introduction Alkene difunctionalization through three-membered ring halonium ion intermediates [1] is an important transformation in organic synthesis. Usually the halonium ions such as bromonium or iodonium ions are generated by

• three-membered ring bromonium ion or iodonium ion. The reaction of 1-X with alkenes followed by the treatment with NaOMe gave the corresponding epoxides as shown in Table 3. Alkenes having an alkoxycarbonyl group gave the corresponding epoxides in moderate yields (Table 3, entries 11–14). Diene 2f

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• and pyran derivatives under indirect electrochemical conditions generating selenium or iodonium cations. The reactions proceed in good yields and regioselectivities for the formation of single diastereomers. Keywords: cyclic ethers; cyclisation; 1,4-dienes; electrochemistry; iodonium; selenium

• the halonium source. Several reactions using bromonium- and iodonium cations such as iodo-etherification, lactonisation or Friedel–Crafts alkylation reactions can be found in literature. However, these procedures often use expensive or toxic halonium sources like molecular bromine [10][28][29] or

• organic trihalide salts [30], N-bromosuccinimide or N-iodosuccinimide and its derivatives [31][32][33][34][35][36], or more specialised reagents such as bis(pyridinium)iodonium(I) tetrafluoroborate [37][38][39]. Next to those, the in situ oxidation of halogenide ions with strong oxidants such as oxone, Pb

Synthesis of the pentasaccharide repeating unit of the O-antigen of E. coli O117:K98:H4

• Pintu Kumar Mandal

Beilstein J. Org. Chem. 2014, 10, 2724–2728, doi:10.3762/bjoc.10.287

•  2). Some of the notable features of this synthetic strategy are (a) application of iodonium ion mediated general glycosylation conditions; (b) nitrosyl tetrafluoroborate (NOBF4) mediated activation of glycosyl trichloroacetimidate donor; (c) the attachment of an aminopropyl linker at the anomeric

• . Compound 10 was reacted with 3-O-PMB protected L-rhamnosylthioglycoside donor 4 and NIS/TfOH [26][27] to yield the trisaccharide derivative by an iodonium ion catalyzed glycosylation. Participation of the 2-O-acetyl group in donor 4 ensured the α-selectivity of the glycosylation. Following an earlier

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• ]. Hydrogen donor coinitiators could be amines [33][34][35][36][37][38], ethers [39][40], sulfides [41][42][43] or thiols [43][44][45]. Electron transfer coinitiators could be borate salts [46][47], iodonium [48][49] or triazine [32] derivatives. However, if Type II PIS gain sensitivity in the visible part of

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• . These PICs are typically used (see below) in combination with various additives (see Figure 3 below) in three-component photoinitiating systems, e.g., based PIC/iodonium salt (or sulfonium salt)/tris(trimethylsilyl)silane (or N-vinylcarbazole) or PIC/amine/alkyl halide. Also, relatively high intensity

• ]. Oxidizable photoinitiator catalysts The oxidation of a PIC is quite easily realized. For example, the excitation of Ru(bpy)32+ (with bpy = bipyridine) in the presence of an iodonium salt (e.g., Ph2I+) as eA leads to Ru(bpy)33+. However, very few systems involving a E-Z structure or a E-Z anion (as suggested

• radical Ph• is formed (Scheme 3). Unfortunately, the oxidation reaction of Ph• by PIC•+ is rather hard [45][46][47][48][49][50][51][52] and such a system does not work. Sulfonium salts were also used as eA but the reactivity is lower than that for iodonium salts (see below) [56]. A typical efficient

Convergent synthesis of a tetrasaccharide repeating unit of the O-specific polysaccharide from the cell wall lipopolysaccharide of Azospirillum brasilense strain Sp7

• Pintu Kumar Mandal,
• Debashis Dhara and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2014, 10, 293–299, doi:10.3762/bjoc.10.26

• orthoester intermediate [38] resulted in the formation of 2-azidoethyl 2,4,6-tri-O-acetyl-β-D-galactopyranoside (2) in 74% yield (Scheme 1). D-Galactosyl acceptor 2 and 3-O-PMB-protected L-rhamnosyl donor 3 were coupled with a stereoselective glycosylation promoted by iodonium ions in the presence of a

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• hydroperoxide group. The treatment of unsaturated monoperoxyketals 257, 260, and 263 (prepared by ozonolysis of 256, 259, and 262 in methanol, respectively) with such donors of halonium ions such as N-iodosuccinimide (NIS), I2/t-BuOK, or bis(sym-collidine)iodonium hexafluorophosphate gave iodine-containing 1,2

• hydroperoxyalkenes 265a–c, 267, and 269a,b with bis(sym-collidine)iodonium hexaflulorophosphate (BCIH) in the cyclization step (Scheme 74). 3.9. Pd(II)-catalyzed cyclization The palladium-catalyzed cyclization of δ-unsaturated hydroperoxides 271 represents a new route to 1,2-dioxane cyclic compounds 272 (Scheme 75

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• bond cleavage of Togni's reagent in presence of the copper catalyst to produce a highly electrophilic species (intermediate A). Then, the acrylate derivative coordinates to the iodonium salt A leading to intermediate B with generation of hydrogen fluoride, followed by an intramolecular reaction between

• the double bond and the iodonium ion to provide intermediate C. The presence of HF in the reaction medium promotes the decarboxylation step in intermediate C, and subsequent reductive elimination leads to the formation of the thermodynamically stable E-alkene. Finally, protonation of intermediate E

Straightforward synthesis of a tetrasaccharide repeating unit corresponding to the O-antigen of Escherichia coli O16

• Manas Jana and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2013, 9, 1757–1762, doi:10.3762/bjoc.9.203

• iodonium ion mediated glycosylation conditions; (c) the use of p-methoxybenzyl (PMB) ether protection as an in situ removable protecting group in a one-pot glycosylation reaction and its removal [17] and (d) the use of galactofuranosidic thioglycoside as a glycosyl donor. The iodonium ion promoted

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

• The direct synthesis of N-arylated carbazoles through a palladium-catalyzed amination of cyclic iodonium salts with anilines is described. In particular, electron-poor aniline derivatives reacted smoothly with only 5 mol % of Pd(OAc)2 as catalyst to give the desired products in up to 71% yield

• . Furthermore, the reactivity of cyclic iodonium salts is compared with the reactivity of the corresponding cyclic bromonium analogues. Keywords: amination; carbazoles; hypervalent; iodine; iodonium salts; Introduction Carbazoles play an important role as core structural elements in natural products (e.g

• ] or the direct arylation [14][15] of the free NH-functionality of carbazole (path B). In the past decade, hypervalent iodine chemistry has undergone a renaissance and has developed to become a powerful area in synthetic organic chemistry. Open-chained iodonium salts are well explored in transition

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• application of two- and three-component photoinitiating systems (different Co_Pys with the addition of iodonium or sulfonium salts, alkyl halide or amine) was investigated in detail for cationic and radical photopolymerization reactions under near-UV–vis light. The proposed compounds can behave as new

• polymerization (ROP) under exposure to the near-UV–vis light delivered by a Hg–Xe lamp (~30 mW cm−2) and the visible light of a halogen lamp (soft irradiation conditions; ~10 mW cm−2) is investigated. The Co_Pys are used in combination with additives: iodonium or sulfonium salts for ROP and amine or/and alkyl

• Co_Py/phenacyl bromide PBr (or the iodonium salt, Iod) interaction is very favorable (ΔG << 0). Py_2 exhibits the most favorable ΔGs: −2.45 eV (Iod) and −1.87 eV (PBr). MO calculations show that the calculated and experimental values (Table 1) are approximately the same, e.g., a difference of 5 to 10 nm

Convergent synthesis of the tetrasaccharide repeating unit of the cell wall lipopolysaccharide of Escherichia coli O40

• Abhijit Sau and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2012, 8, 2053–2059, doi:10.3762/bjoc.8.230

• glycosylation” concept [19][24] (Scheme 2). Iodonium ion promoted [2 + 2] stereoselective glycosylation of compound 8 and compound 9 in the presence of NIS and HClO4–SiO2 [17] furnished tetrasaccharide derivative 10 in 71% yield. Formation of compound 10 was confirmed by its spectral analysis [signals at δ

2-Allylphenyl glycosides as complementary building blocks for oligosaccharide and glycoconjugate synthesis

• Hemali D. Premathilake and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2012, 8, 597–605, doi:10.3762/bjoc.8.66

• of both aryl and pentenyl glycosides, they should offer a more versatile activation profile than either class of the leaving group. Our working hypothesis is that activation of the AP leaving group with I+ takes place by the formation of an epi-iodonium ion, which is then opened with the anomeric

• activated for chemical glycosylation under a variety of conditions including Lewis acid and iodonium ion mediated pathways. The two activation pathways were confirmed by a mechanistic study. We also demonstrated that the application of the AP moiety allows executing oligosaccharide assembly by an orthogonal

Multistep flow synthesis of vinyl azides and their use in the copper-catalyzed Huisgen-type cycloaddition under inductive-heating conditions

• Lukas Kupracz,
• Jan Hartwig,
• Jens Wegner,
• Sascha Ceylan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2011, 7, 1441–1448, doi:10.3762/bjoc.7.168

• reactor at the given flow rates are between 1.5 h to 3.5 h. Mechanistically the good regioselectivity is based on the generation of the more stable carbenium ion after electrophilic attack of the iodonium species on the olefinic double bond. In cases of aliphatic alkenes without aryl substituents

Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

• Abhishek Santra and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2011, 7, 1182–1188, doi:10.3762/bjoc.7.137

• thioethyl group acts as an orthogonal anomeric protecting group since it acts as a glycosyl acceptor in the case of compound 4 whereas compound 7 has been used as the glycosyl donor in the next step. Iodonium ion promoted stereoselective glycosylation of the disaccharide thioglycoside donor 7 with the

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

• syntheses as mild, non-toxic and highly selective reagents. Iodine(III) reagents with two carbon ligands are known as iodonium salts. These salts are attractive alternatives to oxidants and catalysts based on heavy metals, as they have similar properties to those of heavy metal complexes and can, therefore

• , be used in similar reaction pathways, and are beneficial for organic synthesis due to their low toxicity and cost [20]. Iodonium salts are currently being used in three main types of reactions, namely ligand exchange, reductive elimination and ligand coupling. This is due to their highly electron

• increase the selectivity of the coupling reaction [21]. The sulfuric acid acts both as a counter reaction to the oxidation at the anode, with proton reduction, and simultaneously provides a counter ion for the positively charged iodonium salt. It also acts as an electrolyte in the reaction described above

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• domino processes, for which gold pre-catalysts were found to be outstandingly effective, were paralleled by employing iodine electrophiles in place of gold compounds. This review highlights how, in certain cases, iodonium activation can match gold-catalyzed reactions to construct identical product

• scaffolds. Likewise, processes are discussed where mostly identical starting materials are transformed into diverse frameworks depending on whether gold or iodonium activation was used to trigger the reaction. Keywords: catalysis; cycloisomerizations; domino reactions; gold; iodine; Introduction Over the

• reactions [41][42]. As a logical extension, one might speculate about analogous processes triggered by direct iodonium activation in the absence of gold catalysts (Scheme 1c). Since Barluenga, Larock, and others have shown over the last decades that various cyclizations of carbon and heteroatom nucleophiles

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• resulted in good yields [4][26]. Copper-diamine-catalysed N-arylation facilitated the arylation of pyrroles, pyrazoles, indazoles, imidazoles, triazoles, benzimidazoles and indoles [27][28][29]. Besides aryl halides as the aryl donor, arylsiloxanes [30], arylstannanes [31], iodonium salts [32], aryl lead

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• , enamines, and thiolate anions with these reagents, albeit in low to moderate yields [28]. Neutral hypervalent iodine(III)–CF3 reagent Initial attempts by Yagupolskii and Umemoto to synthesize iodonium salts with a trifluoromethyl group were unsuccessful. Whilst iodonium salts including p