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

• ; in other words, the diazonium salt is generated from the corresponding aromatic amine (preparation of the reagent), and then the aryl radical is added to the graphene sheet. The crucial parts of a significant number of the articles on the application of GO and RGO focus on the chemical

• researchers have discussed the reaction pathway [49][50]. Most plausibly, the reaction can be mainly attributed to rapid reactions based on electron-transfer processes. The first step of the diazotization reaction involves the generation of a diazonium salt from the corresponding amino reagent using a nitrite

• species (Figure 7, step a). Then (most likely) the aryl radical is obtained from the diazonium salt via the single electron transfer (SET) process and the inclusion of a graphene sheet (Figure 7, step b). This reaction step results in nitrogen extrusion. The desired functionalization route is most

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• -pyridinyl derivative 1d was obtained in low yield by the reaction of the trifluoroborate 3b with the diazonium salt 4d at 80 °C in DMF with Pd(PPh3)4 as a catalyst (Table 1, entry 9). It should be noted that some of these Suzuki–Miyaura coupling reactions require relatively long reaction times (Table 1

• , entries 6–9), which is a disadvantage considering the competing decomposition of the aryldiazonium ions under the reaction conditions. Thus, the corresponding diazonium salt was added in portions in intervals of 24 h until all of the substrate was consumed. Synthesis of 9-(arylethynyl)benzo[b

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

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

• , generated through copper-mediated single electron transfer from diazonium salt A, released nitrogen gas affording the aryl radical C. On the other hand, the CF3 radical was generated through the reaction of TBHP with NaSO2CF3 in the presence of Cu(I) species. Then, the CF3 radical reacted with the Cu(I

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

• (Scheme 35) [70]. o-Methylthioaryl diazonium salts and phenylacetylene are starting materials, and photoexcited Eosin Y transfers an electron to the diazonium salt, which decomposes into a reactive aryl radical and N2. Addition to the acetylene yields a vinylic radical intermediate, which cyclizes to the

• from alkyl and aryl thiosulfates and aryl diazonium salts (Scheme 39) [74]. They confirmed by transient absorption spectroscopy that a single-electron transfer occurs between [Ru(bpy)3]Cl2 and the aryl diazonium salt. Additionally, electron paramagnetic resonance studies showed that K2CO3 interacts

• oxidatively quenched by the aryl diazonium salt, generating [Ru(bpy)3]3+ and an aryl radical intermediate. The radical addition to DMSO and subsequent single-electron oxidation, either by regenerating the photocatalyst or by forming a new aryl radical from the aryl diazonium salt, leads to a sulfur-centred

¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• ) was used to incorporate isotopic labels in the tetrazolo[1,5-b][1,2,4]triazine core (Scheme 1). The interaction of diazonium salt 8-15N2 derived from [2,3-15N2]-5-aminotetrazole 7-15N2 with ethyl α-formylphenylacetate (9) yielded compound 10-15N2. It was expected that the cyclization of 10-15N2 would

• 16-15N (98%, 15N) and labelled sodium nitrite (98%, 15N) in acidic medium allowed for the in situ production of diazonium salt 17-15N2, which reacted with ethyl nitroacetate (18) in a sodium carbonate solution (Scheme 2). This reaction led to the formation of [1,5-15N2]-1,2,4-triazolo[5,1-c][1,2,4

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

• the diazonium salt 1a and B2pin2 (2) was milled for 2 h at 25 Hz in a mixer mill, using a Teflon milling jar and ZrO2 ball bearings. The safe use of diazonium salt under ball milling conditions has been previously reported in the literature [19]. The analysis of the reaction mixture by 1H NMR

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

• with various alkenes [5], which prompted us to disclose our results in this communication. Results and Discussion When we reacted diazonium salt 2a with methyl methacrylate (3a) in acetonitrile in the presence of a catalytic amount of Ru(bpy)3Cl2 under blue laser irradiation, we could isolate

• isochromanone 4a in 72% yield (Scheme 2 and Table 1). Analogous results were obtained when the substitution pattern on both the diazonium salt and the alkene was varied, results that paralleled those reported by König and Fagnoni [5]. In our hands reactions were slower (6–8 h vs 2 h), probably due to the lower

• 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

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

• derivatives in alkaline reaction conditions, the synthesis of 1-((2,4-dimethylphenyl)azo)naphthalen-2-ol (19) also commonly known as Sudan II azo dye was used as a model reaction. The synthesis involved diazotization of 2,4-dimethylaniline (16) to form diazonium salt intermediate 17, which is coupled with 2

• the azo compound. However, highly alkaline conditions are usually avoided as they lead to diazonium salt decomposition. In the regression summary of the statistical data analysis (Table 2) of the observed data, it is seen from the p-values (0.067 and 0.084) associated with the estimated coefficients

• temperature of 25 °C, excellent conversions were attained in the azo coupling reaction of the diazonium salt solution of 2,4-dimethylaniline to 2-naphthol whereas the azo coupling reaction of the diazonium salt solution of p-nitroaniline to diphenylamine was found to thrive at a pH of 5.71 and at a

Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

• Norbert Vida,
• Jiří Václavík and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 110–116, doi:10.3762/bjoc.12.12

• toward 4 was prepared independently (Scheme 4). Azo coupling [20] of phenol 11 with a diazonium salt prepared from sulfanilic acid afforded red azo product 13. The regioselectivity is governed by the strong para-directing hydroxy group despite the presence of the bulky SF5 group. Compounds with

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• catalyst and the appropriate organoborane to give the expected product with 47 and 78% yield for the chloride and triflate substrates, respectively. The nitro function present in the product was then reduced by palladium-catalyzed hydrogenation to yield the amine product converted into a diazonium salt. A

• Japp–Klingemann reaction was used to transform the diazonium salt in the presence of ethyl 2-methyl-3-oxobutyrate into the respective hydrazone. The indole was formed from the treatment of the hydrazone with polyphosphoric acid. The last heterocyclic ring was formed by an intramolecular reaction of the

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

• pyridinium tetrafluoroborate radical and the Bpin radical. Subjecting the diazonium salt 3i to the borylation conditions gave further indirect evidence for the formation of aryl radicals (Scheme 3). Full conversion of 3i was observed affording a mixture of products 2i, 2i’, 5i (two isomers of unknown

• conditions: 3 (1 mmol), B2pin2 (1 mmol), pyridine (4 mmol), MeCN (2 mL), 2 h. Proposed reaction mechanism. Reaction of diazonium salt 3i under borylation conditions. Suzuki–Miyaura reaction of boronates 2a and 2b with aryl iodides. Reaction conditions: 2 (1 mmol), ArI (1.1 mmol), Pd(PPh3)4 (5 mol

Azobenzene-based inhibitors of human carbonic anhydrase II

• Leander Simon Runtsch,
• David Michael Barber,
• Peter Mayer,
• Michael Groll,
• Dirk Trauner and
• Johannes Broichhagen

Beilstein J. Org. Chem. 2015, 11, 1129–1135, doi:10.3762/bjoc.11.127

• enzyme affinity. Results and Discussion Azobenzenes can be synthesized by a variety of known chemical transformations [8]. Among them the most widely used is the diazotization of aniline, followed by trapping of the diazonium salt with an electron-rich aromatic compound (such as anilines and phenols

• characterization of azobenzene-containing aryl sulfonamides by different strategies. a) Diazotization and trapping of the diazonium salt with an electron-rich aromatic compound yields azobenzenes 1a–c. b) Reaction of methylene sulfonate-protected aniline and one-pot deprotection yields 1d, which can be converted

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

• 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

• were rather less reactive under these conditions, and products were obtained with low to modest yields [9]. Previously, we described a novel type of diazonium salt – arenediazonium tosylates (ADT), which differ from arenediazonium tetrafluoroborates in their higher stability at a dry state and their

Halogenated volatiles from the fungus Geniculosporium and the actinomycete Streptomyces chartreusis

• Tao Wang,
• Patrick Rabe,
• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2767–2777, doi:10.3762/bjoc.9.311

• diazonium salt followed by a Sandmeyer reaction resulted in 4b (61% over two steps). The isomer 4c was efficiently prepared by double methylation of 2-chlororesorcinol (8) with potassium carbonate and methyl iodide in acetone (88%), while 4f was obtained by chlorination of dimethoxybenzene 9 with

Ethyl diazoacetate synthesis in flow

• Mariëlle M. E. Delville,
• Jan C. M. van Hest and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2013, 9, 1813–1818, doi:10.3762/bjoc.9.211

• elimination of the sulfone substituent. Additionally, Ley et al. [19] recently prepared a range of α-hydroxy acids in flow starting from the corresponding amino acids, involving diazotization of the amine to the diazonium salt in a biphasic system. Inspired by Ley’s approach, which is significantly more atom

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

• substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by

• using a more reactive diazonium salt before a less reactive one. Keywords: azo coupling; diazonium salt; enaminone; pyridazinium; Introduction As heterocyclic compounds play a very important role in everyday life, e.g., as pharmaceuticals, agrochemicals, dyes, etc. (for many monographies or textbooks

• -methylbenzenediazonium tetrafluoroborate under the same conditions as described in [8] (i.e., DCM, rt, 2 equiv of diazonium salt, 6 equiv of sodium acetate) afforded the corresponding pyridazinium salt 5a in 36% yield. The same procedure applied to the benzoylacetone derivative 3b gave even lower yield (19%) of the salt

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction

• George Iakobson and
• Petr Beier

Beilstein J. Org. Chem. 2012, 8, 1185–1190, doi:10.3762/bjoc.8.131

• cyclized product 10d resulting from electrophilic aromatic substitution of the substituted phenyl cation intermediate (formed by the decomposition of the diazonium salt), to the electron-rich anisole ring in an unusual meta-position relative to the methoxy group. The more activated para-position is

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• roles of the benzene and pyridine rings, with the former as the nucleophile and latter as electrophile through the diazonium salt, led to improved yields in the indole ring closure [41], as did microwave promotion of the original methodology [42]. Nitrene insertion chemistry of appropriately substituted

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• indole synthesis a hydrazine, which is most commonly derived from the corresponding diazonium salt, is reacted with a suitable carbonyl compound. Alternatively, the Japp–Klingemann reaction can be used to directly couple the diazonium salt with a β-ketoester to obtain a hydrazone which can then undergo

• to both these syntheses making them more economic and environmentally benign. For example, the three steps to zolmitriptan, namely, diazonium salt formation, its subsequent reduction and Fischer indole synthesis can all be carried out in aqueous media without the need for intermediate isolation. It

• has also been demonstrated that the reduction of the initially formed diazonium salt can be accomplished by using sodium metabisulfite (Na2S2O5) rather than using the more toxic stannous chloride or the less water soluble and more expensive sodium sulfite. Preparation of the indole ring system in 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

• and sodium nitrite in water at 0–5 °C to provide an intermediate diazonium salt. The latter underwent cycloaddition with an isocyanate in a one-pot reaction to give compound 43 (Scheme 10) [41]. 5-Aminopyrazoles 45 have recently been prepared by Boc deprotection of the α-hydrazino acids 44 with TFA in

Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst

• Guangming Nan,
• Fang Ren and
• Meiming Luo

Beilstein J. Org. Chem. 2010, 6, No. 70, doi:10.3762/bjoc.6.70

• a solution of NaNO2 (10 mmol) in cold water (1 mL) was added dropwise. The resulting solution of the diazonium salt was stirred in the cold for 10 min and then added all at once to a chilled solution of pyrrolidine (11 mmol) in 1 M KOH (10 mL). The reaction mixture was stirred for 30 min with

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

• -trifluoromethylation of phenol by diazonium salt 19a. Effect of the counteranion. Thermal O- and N-trifluoromethylations. Method of preparation of S-(trifluoromethyl)diphenylsulfonium triflates. Reactivity of some S-(trifluoromethyl)diarylsulfonium triflates. One-pot synthesis of S-(trifluoromethyl)diarylsulfonium

Reduction of arenediazonium salts by tetrakis(dimethylamino)ethylene (TDAE): Efficient formation of products derived from aryl radicals

• Mohan Mahesh,
• John A. Murphy,
• Franck LeStrat and
• Hans Peter Wessel

Beilstein J. Org. Chem. 2009, 5, No. 1, doi:10.3762/bjoc.5.1

• vinblastine (58a) and vincristine (58b) contain such a system. Aryl C-C bond formation As a final extension of this methodology, we probed the feasibility of this methodology in aryl-aryl C-C bond formation reactions. Accordingly, the diazonium salt 62 was prepared from indoline (59), and treated with one

• could also undergo direct formation of the radical 69. Rearomatization from 69 might then occur through a number of pathways; in one of these, the radical intermediate 69 would lose a proton to yield the radical anion 70 which, upon oxidation by loss of single electron to the starting diazonium salt 62