Cobalt bis(acetylacetonate)–tert-butyl hydroperoxide–triethylsilane: a general reagent combination for the Markovnikov-selective hydrofunctionalization of alkenes by hydrogen atom transfer

• Xiaoshen Ma and
• Seth B. Herzon

Beilstein J. Org. Chem. 2018, 14, 2259–2265, doi:10.3762/bjoc.14.201

• -methoxybenzoate (3c, not shown) afforded the azo compounds 7a and 7c in 92% and 91% yields, respectively. By comparison the yield of the azo product using allyl p-methoxybenzoate (3b, now shown) as substrate was somewhat lower (77%). Diazonium salts bearing substituents with different steric and electronic

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• publication by Kundu and Ranu provides a way of arylating the C2 position of electron-rich five-membered heterocycles, using anilines as the coupling partner. tert-Butyl nitrite (t-BuONO) is used as a diazotizing agent to generate diazonium salts transiently in situ. The reaction is catalysed by Eosin Y under

• , benzothiophenes and benzimidazoles seen in many drugs. In another demonstration of the value of diazonium salts, the König group have published a protocol for the synthesis of substituted benzothiophenes using Eosin Y photocatalysis, starting from o-methylthioarenediazonium salts and substituted alkynes (Scheme

Functionalization of graphene: does the organic chemistry matter?

• Artur Kasprzak,
• Agnieszka Zuchowska and
• Magdalena Poplawska

Beilstein J. Org. Chem. 2018, 14, 2018–2026, doi:10.3762/bjoc.14.177

• Artur Kasprzak Agnieszka Zuchowska Magdalena Poplawska Faculty of Chemistry, Warsaw University of Technology, Noakowskiego Str. 3, 00-664 Warsaw, Poland 10.3762/bjoc.14.177 Abstract Reactions applying amidation- or esterification-type processes and diazonium salts chemistry constitute the most

• commonly applied synthetic approaches for the modification of graphene-family materials. This work presents a critical assessment of the amidation and esterification methodologies reported in the recent literature, as well as a discussion of the reactions that apply diazonium salts. Common

• common misunderstandings and inaccuracies. This work deals with common issues in the field of GO and RGO functionalization; it discusses the carboxyl-based approach and includes remarks regarding reactions that utilize diazonium salts. Direct links are provided to basic principles of organic synthesis

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• proceeded via radical intermediates (Scheme 25), which is analogous to Sandmeyer halogenations of diazonium salts. First, the trifluoromethyl copper(I) species is generated from TMSCF3 and copper salt. Then, Cu(I)CF3 transfers one electron to the diazonium salt affording Cu(II)CF3 and a diazo radical

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

• different strategy for the photoredox-catalyzed preparation of diaryl sulfides was reported in 2013, applying [Ru(bpy)3]Cl2 as photocatalyst (Scheme 16) [47]. The authors propose a mechanism where in situ generated aryl diazonium salts are cleaved by reduction of the excited state of the photocatalyst to

• benzoxazoles. Starting from aryl thiols and aryl diazonium salts, Lee and co-workers developed a visible-light photocatalyzed procedure for the preparation of diaryl sulfides (Scheme 17) [48]. Applying Eosin Y as organic photocatalyst, both electron-rich and electron-deficient thiols reacted well with various

• aryl diazonium salts to give the corresponding diaryl sulfide in high yields. Very recently, Noël and co-workers applied the above-mentioned concepts for the selective arylation of cysteine and cysteine-containing peptides in batch as well as in a photomicroreactor (Scheme 18) [49]. They were able to

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• simple alkenes, sodium triflinate and diazonium salts. The CF3 radical was produced from CF3SO2Na by oxidation with H2O2 in the presence of silver nitrate. Then, CF3• was added to the terminal position of the alkene to give radical 26 that was trapped by the arenediazonium salt to form the radical cation

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• have used KOH as base, neutral alumina as milling auxiliary. Both electron-donating and -withdrawing diazonium salts worked efficiently to give 70–90% of the products (Scheme 43) [171]. This solvent-free mechanomilling strategy reported to be superior to any solution phase synthesis because it avoids

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• mechanistic studies suggest that catalyst F1 favours enol formation of starting material 4, thus providing a convincing rational why no base is required for this transformation [79]. Another class of easily accessible electrophilic N-transfer reagents are (aryl)-diazonium salts like compounds 41. The control

Mechanochemical borylation of aryldiazonium salts; merging light and ball milling

• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1463–1469, doi:10.3762/bjoc.13.144

• . bAfter column chromatography. Screening of the reaction conditions.a Borylation of aryl diazonium salts 1 with 2.a Supporting Information Supporting Information File 194: Experimental procedures, experimental set-ups and characterization data, NMR spectra, and DSC traces. Acknowledgements This research

Photocatalyzed synthesis of isochromanones and isobenzofuranones under batch and flow conditions

• Manuel Anselmo,
• Lisa Moni,
• Hossny Ismail,
• Davide Comoretto,
• Renata Riva and
• Andrea Basso

Beilstein J. Org. Chem. 2017, 13, 1456–1462, doi:10.3762/bjoc.13.143

• -diphenylethanol was isolated, although the origin of water was not clear (possibly trapped by the diazonium salts during crystallization since, due to their potential explosivity in the dry state, they were not dried under vacuum). At this stage we postulated that A could be more favourably attacked in an

• loading of photocatalyst (0.5% vs 2%) and excess of alkene (2 equiv vs 3 equiv) employed; moreover, the use of an inert atmosphere did not lead to significant improvements. No differences were observed when the 440 nm laser was replaced by blue LEDs (maximum wavelength 455 nm). Diazonium salts were

• methyl/ethyl esters of diazonium salts derived from anthranilic acids were completely soluble in acetonitrile and other solvents such as acetone or toluene. Moreover, these salts were also more easily synthesized starting from the corresponding methyl/ethyl anthranilates. To our delight diazonium salt 2b

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

Chemoselective synthesis of diaryl disulfides via a visible light-mediated coupling of arenediazonium tetrafluoroborates and CS₂

• Jing Leng,
• Shi-Meng Wang and
• Hua-Li Qin

Beilstein J. Org. Chem. 2017, 13, 903–909, doi:10.3762/bjoc.13.91

• has also been studied [14][15] by taking advantage of visible light as abundant and environmentally friendly energy source for organic syntheses. The photochemistry of diazonium salts has been widely studied since the early 19th century, at which time, it was noticed that benzenediazonium nitrate

• turns red upon exposure to sunlight due to decomposition and formation of radical species [20]. Subsequently, the photodecomposition of diazonium salts by loss of nitrogen upon exposure to light has been utilized in organic synthesis for example to remove amino groups from anilines [21] or for arylation

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• have applied a Heck-reduction–cyclization–alkylation (HRCA) methodology under mild and simple reaction conditions. First, diazonium salts 56 underwent the Heck reaction with methyl vinyl ketone (57) to give the cross-coupling products 58 followed by hydrogenation of the latter to give aromatic

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors

• Faith M. Akwi and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 1987–2004, doi:10.3762/bjoc.12.186

• -naphthol. The method boasts of shorter reaction times [4] with high yields (Scheme 2). Mirjalili et al. also used silica supported boron trifluoride and was able to carry out diazotization at room temperature [5] after they discovered that the diazonium salts obtained were stable at room temperature even

• be changed or modified to achieve the above mentioned green benefits in addition to other advantages. For example, isolated diazonium salts are known to be hazardous due to their explosive and unstable nature. However, microreactor technology makes it possible to safely perform reactions with

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

• )phenylboronic esters, iodo(pentafluorosulfanyl)benzenes and (pentafluorosulfanyl)benzene is shown. Keywords: borylation; diazonium salts; iodination; pyridine; sulfur pentafluorides; Introduction Pentafluorosulfanyl-containing compounds have been known for more than half a century [1][2][3][4]; however, for a

• ][58], Lewis acid catalyzed electrophilic borylations of electron-rich arenes [59][60][61][62], and Sandmeyer-type borylation of arylamines or diazonium salts with B2pin2 [63][64][65][66][67], B2(OH)4 [68] or R2N-BH2 [69]. Several attempts were made to synthesize the SF5-phenylboronates. Patent

• access to SF5-phenylboronates appears to be starting from readily available SF5-substituted anilines or diazonium salts rather than SF5-containing halobenzenes. Herein, we report a new protocol for efficient borylation, iodination and hydrodediazoniation of SF5-phenyldiazonium tetrafluoroborates in the

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• hydroperoxometallic intermediaite 15 which decomposes to azoxy product 16 and palladium hydroxide complex 17. The degradation of the azoxy product 16 can afford quinolinones and diazonium salts as it established by many authors [38][39][40]. Conclusion In summary, new palladium-complexes using oxazolines as ligands

Matsuda–Heck reaction with arenediazonium tosylates in water

• Ksenia V. Kutonova,
• Marina E. Trusova,
• Andrey V. Stankevich,
• Pavel S. Postnikov and
• Victor D. Filimonov

Beilstein J. Org. Chem. 2015, 11, 358–362, doi:10.3762/bjoc.11.41

• for the first time. A range of alkenes was arylated in good to quantitative yields in water. The reaction is significantly accelerated when carried out under microwave heating. The arylation of haloalkylacrylates with diazonium salts has been implemented for the first time. Keywords: alkyl cinnamates

• ; diazonium salts; Matsuda–Heck reaction; microwave-assisted synthesis; stilbenes; Introduction Diazonium salts are known as one of the most valuable building blocks in organic synthesis [1]. Today, their most common use is the construction of carbon–carbon bonds in palladium-catalyzed reactions. Starting

• with the work of Matsuda’s group [2], who used a diazonium salt as a high-reactive electrophile for a Heck reaction, the Matsuda–Heck reaction does require the addition of neither bases nor ligands and is carried out under very mild conditions [3]. Furthermore, diazonium salts are more often prepared

Synthesis of nanodiamond derivatives carrying amino functions and quantification by a modified Kaiser test

• Gerald Jarre,
• Steffen Heyer,
• Elisabeth Memmel,
• Thomas Meinhardt and
• Anke Krueger

Beilstein J. Org. Chem. 2014, 10, 2729–2737, doi:10.3762/bjoc.10.288

• and the aminated moiety. One commonly used method is the (in situ) formation of aromatic diazonium salts and the reaction of the aryl residue with π-bonds, hydrogenated sites or various surface groups (in this case via heteroatoms) on the diamond surface [8][9][10]. Recently, we have reported an

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• different mechanisms in these aromatic substitution reactions with arene diazonium salts. The redox potentials of most substituted arene diazonium salts cluster with very little deviation around 0.0 V vs. SCE (±0.2 V) [23][24] so that the observed differences in Φ can be largely attributed to different

• -catalyzed substitutions with arene diazonium salts. Acid–base behaviour of eosin Y. Eosin Y-catalyzed and dye-free photolytic borylation. Eosin Y-catalyzed and dye-free reactions with ethyl propiolate. Quantum yield determinations of selected visible-light-driven aromatic substitutions. Supporting

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• the [Au(I)]/[Au(III)] redox couple during the intramolecular oxy- and aminoarylation of alkenes (Scheme 40) [86]. Optimal conditions for the reaction involved the use of Ph3PAuNTf2 in presence of [Ru(bpy)3]2+ as redox photocatalyst and aryl diazonium salts 157. In the proposed tandem catalytic cycle

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

• František Josefík,
• Markéta Svobodová,
• Valerio Bertolasi and
• Petr Šimůnek

Beilstein J. Org. Chem. 2013, 9, 1463–1471, doi:10.3762/bjoc.9.166

• Diffratometrica, Università di Ferrara, Via L. Borsari 46, 441 00, Ferrara, Italy 10.3762/bjoc.9.166 Abstract Easily obtainable cyclic enaminones (piperidin-2-ylidenealkanones) can be transformed into substituted bicyclic pyridazinium tetrafluoroborates upon treatment with corresponding diazonium salts. The

• in heterocyclic chemistry (for many reviews see, e.g., [2][3][4][5][6]). During the past several years we have dealt with the reaction of various enaminones with diazonium salts and established a number of methods for the construction of some important or unusual heterocyclic systems [7][8][9][10][11

• this, reactions of enaminones with diazonium salts giving substituted pyridazines are also described [25][26][27][28]. Our method does not require any additive, and the transformation from 1 to 2 is performed as a one-pot procedure. Different substrates are used and different and novel pyridazinium

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

• Silvia M. Soria-Castro and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2013, 9, 467–475, doi:10.3762/bjoc.9.50

• ] and sulfonamides [49]. Thioacetate and thiobenzoate derivatives have been synthesized by the reactions of thioacetate and thiobenzoate anions with arenediazonium tetrafluoroborates [50]. However, this methodology implies moderate overall yields and the handling of usually unstable diazonium salts

Synthesis of oleophilic electron-rich phenylhydrazines

• Aleksandra Jankowiak and
• Piotr Kaszyński

Beilstein J. Org. Chem. 2012, 8, 275–282, doi:10.3762/bjoc.8.29

• obtained by using classical methods, such as the reduction of diazonium salts [13][14][15]. In contrast, electron-rich arylhydrazines are far less numerous and their preparation is complicated by oxidative instability. To access functionalized and sensitive arylhydrazines several methods involving the

Approaches towards the synthesis of 5-aminopyrazoles

• Ranjana Aggarwal,
• Vinod Kumar,
• Rajiv Kumar and
• Shiv P. Singh

Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25

• coupling with aromatic diazonium salts gave the corresponding 2-arylhydrazones 47, which on treatment with hydrazine hydrate formed the 5-amino-4-arylazopyrazoles 48. 3-Oxo-3-(pyrrol-2-yl)propanenitrile (16) reacted with trichloroacetonitrile to yield enamine 49, which on further treatment with hydrazine

• -Iminobutyronitrile (55) couples with aromatic diazonium salts in a similar manner to yield 2-arylhydrazono-3-iminobutyronitriles 56. Treatment of hydrazones 56 with hydrazine hydrate in refluxing ethanol afforded the corresponding 5-amino-4-arylazo-3-methylpyrazoles 57 in good yields [45]. Pyrazoles 57 further