Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• (PMMA) jar (Scheme 8) [72]. As far as the irradiation source is concerned, the authors wrapped a LED strip around the jar. A solution-based precedent by the Yan group was used as a benchmark transformation [73]. Under optimized conditions, a mixture of diazonium salt 8.1, B2Pin2 (1.5 equiv) and eosin Y

Electrochemical synthesis of cyclic biaryl λ³-bromanes from 2,2’-dibromobiphenyls

• Andrejs Savkins and
• Igors Sokolovs

Beilstein J. Org. Chem. 2025, 21, 451–457, doi:10.3762/bjoc.21.32

• required thermal decomposition of the diazonium salt to effect the cyclization. In the quest for mild (room temperature) and scalable conditions toward cyclic diaryl λ3-bromanes 1 we realized that bromanyl units possess leaving group abilities comparable to the diazonium moiety [1][15]. Hence, the

Synthesis, characterization, and photophysical properties of novel 9‑phenyl-9-phosphafluorene oxide derivatives

• Shuxian Qiu,
• Duan Dong,
• Jiahui Li,
• Huiting Wen,
• Jinpeng Li,
• Yu Yang,
• Shengxian Zhai and
• Xingyuan Gao

Beilstein J. Org. Chem. 2024, 20, 3299–3305, doi:10.3762/bjoc.20.274

• % yield over 2 steps) [34]. Upon exposure to NaNO2/HCl, diamine 3 was transformed into a diazonium salt, which was captured by KI to deliver the diiodide 4. Treatment of 4 with n-BuLi, PhPCl2, and H2O2 sequentially gave 2,8-difluoro-5-phenylbenzo[b]phosphindole 5-oxide (5) in 68% yield. With compound 5 in

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• (75) with 4-bromobenzenediazonium tetrafluoroborate (76) (Figure 15a and 15b). In contrast, negligible product (5%) was formed in the absence of light. When light was present but H2TPP (18) was absent, the yield was only 8%, likely due to light-triggered heterolysis of the diazonium salt, which

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• applied to other small compounds developed in our laboratory [34]. Selenoindirubin-N-glycososides 3-Acetoxybenzo[b]selenophene (36f) was prepared in our group according to a literature procedure (Scheme 22) [35][36][37]. The synthesis is based on the reaction of disodium diselenide with the diazonium salt

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

Synthesis of substituted triazole–pyrazole hybrids using triazenylpyrazole precursors

• Simone Gräßle,
• Laura Holzhauer,
• Nicolai Wippert,
• Olaf Fuhr,
• Martin Nieger,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2024, 20, 1396–1404, doi:10.3762/bjoc.20.121

• cycloaddition of the gained synthesized azidopyrazoles with different alkynes was to be conducted. The 3-(3,3-diisopropyltriaz-1-en-1-yl)-1H-pyrazole precursors 15a–d were synthesized according to previously reported procedures [3][26][27] via the generation of a diazonium salt from aminopyrazoles 14a–d

Enantioselective synthesis of β-aryl-γ-lactam derivatives via Heck–Matsuda desymmetrization of N-protected 2,5-dihydro-1H-pyrroles

• Arnaldo G. de Oliveira Jr.,
• Martí F. Wang,
• Rafaela C. Carmona,
• Danilo M. Lustosa,
• Sergei A. Gorbatov and
• Carlos R. D. Correia

Beilstein J. Org. Chem. 2024, 20, 940–949, doi:10.3762/bjoc.20.84

• previous works [18], the oxidation step is practical and high-yielding, and the overall yield can be reported based on the isolated lactams. By evaluating the electronics of the diazonium salt, we observed that the electron-donating p-OMe substituent performed better (4aa, 68% yield) when compared to

Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

• Nedra Touj,
• François Mazars,
• Guillermo Zaragoza and
• Lionel Delaude

Beilstein J. Org. Chem. 2023, 19, 1947–1956, doi:10.3762/bjoc.19.145

• mesitylamine with sodium nitrite and acetic acid followed by a substitution of the intermediate diazonium salt with sodium azide [68]. All our attempts to prepare 2-azido-1,3-diisopropylbenzene along the same lines failed. Nevertheless, its in situ formation in the presence of phenylacetylene led to the

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• two options for the generation of 4-ethoxy-2,3,6-triaminopyridine (9). One possibility comprised the deprotection of the dicarbamate 5 with potassium hydroxide giving the diamine 6, followed by azo coupling with the diazonium salt obtained from aniline and sodium nitrite to give azo compound 7

Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes

• Nicolai Wippert,
• Martin Nieger,
• Claudine Herlan,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187

• . Diisopropylamine and an aqueous solution of potassium carbonate were added to the in-situ generated diazonium salt according to literature-known protocols [40]. The resulting 3-(3,3-diisopropyltriaz-1-en-1-yl)-1H-pyrazole-4-carbonitrile (15) was used as starting material for the attempts to add different side

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• effectiveness of our strategy, the necessity of isolating the potentially hazardous diazonium salt may be seen as an important disadvantage. Arylating the quinone starting directly from the aniline in a one-pot procedure would effectively avoid the need for isolation of the potentially explosive salt and

• not alter the outcome. The diazonium salt derived from the electron-rich 4-anisidine (4j) proved to be less reactive, requiring 48 hours of reaction time. Compared to other substrates, reacting the chlorinated quinone with unsubstituted aniline (4l) resulted in substantially more side products

(Phenylamino)pyrimidine-1,2,3-triazole derivatives as analogs of imatinib: searching for novel compounds against chronic myeloid leukemia

• Luiz Claudio Ferreira Pimentel,
• Lucas Villas Boas Hoelz,
• Henayle Fernandes Canzian,
• Frederico Silva Castelo Branco,
• Andressa Paula de Oliveira,
• Vinicius Rangel Campos,
• Floriano Paes Silva Júnior,
• Rafael Ferreira Dantas,
• Jackson Antônio Lamounier Camargos Resende,
• Anna Claudia Cunha,
• Nubia Boechat and
• Mônica Macedo Bastos

Beilstein J. Org. Chem. 2021, 17, 2260–2269, doi:10.3762/bjoc.17.144

• )pyrimidin-2-amine (5) was obtained from the aromatic nucleophilic substitution reaction of intermediate PAPP via the formation of a diazonium salt with 84% yield, which was characterized, and its data agreed with those in the literature [29]. The carbonyl nucleophilic substitution reaction between

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• ) tetrafluoroborate (138) in the presence of HBF4 and NaNO2 at 0 °C. Next, the nanoparticles were obtained from the reduction of Pd(OAc)2 and Cu(OAc)2 employing NaBH4 in the presence of diazonium salt [63]. A possible mechanism for the synthesis of polycyclic triazoles 142 was proposed by Sekar et al. as well [63

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

• Rashmi Singh,
• Tomas Horsten,
• Rashmi Prakash,
• Swapan Dey and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

• , Belgium 10.3762/bjoc.17.79 Abstract Several new heterocyclic systems based on a hydroxybenzofuro[2,3-b]pyridine building block were prepared. This benzofuropyridine is easily available from the Meerwein reaction of benzoquinone and a heterocyclic diazonium salt, followed by reduction and cyclization

• aminoheterocycles [38]. Alternatively, the classical Meerwein reaction can be applied starting from 3-amino-2-chloropyridine (10), which was transformed into the diazonium salt and coupled in situ with 1,4-benzoquinone, forming arylated quinone 11 without an additional reducing agent [39]. The quinone was reduced

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

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• occurring on a stilbene diazonium salt (e.g., 1.1+) with the intermediacy of an aryl radical [40]. Alternative strategies for the synthesis of phenanthrenes have been later reported, including the adoption of [4 + 2] benzannulations between biaryl derivatives and alkynes [41][42]. Scheme 2 illustrates one

• of such cases where an aryl radical, formed via the photocatalyzed reduction of diazonium salt 2.1+, added to methyl propiolate. Ensuing cyclization of the resulting vinyl radical 2.2· finally yielded the desired phenanthrene 2.3 [41]. A different approach involves the intramolecular cyclization of α

• involved the formation of a C(sp2)–C(sp2) bond via an aryl radical intermediate (Scheme 11). Thus, compound 11.1 was in situ converted to the corresponding diazonium salt 11.2+, which, upon reduction and nitrogen extrusion, formed the reactive aryl radical 11.3·. In turn, the latter radical smoothly

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

• )aryldiazonium salts, a panel of difluoromethylated arenes and heteroarenes was obtained (26 examples, up to 84% yield). Note that the transformation was also carried out starting from 4-methoxyaniline followed by the in situ formation of the corresponding diazonium salt. In the same vein, the authors used this

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• with very good to excellent yields. The authors postulated the in situ formation of CuSeCF3 as the catalytically activated species that was able to reduce the diazonium salt and transfer SeCF3. Trifluoromethylselenyl chloride (ClSeCF3) and trifluoromethyltolueneselenosulfonate (TsSeCF3) Known since the

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• of sulfur dioxide. DABSO was selected as it would provide a facile method and is a safer alternative to sulfur dioxide gas [7][8][9][10]. The target molecule 4 was envisaged via the diazonium salt of 5 [11] and 6 and was a modification of the microfluidic flow reaction reported by Malet-Sanz et al

• originally present in the diazonium salt. The direct diazotisation of 5 was performed using anhydrous organic solvents and t-BuONO at −10 °C in the presence of CuCl2 (method a) and the classical NaNO2/HCl method b in the absence of CuCl2, as shown in Scheme 3. Compound 8 was obtained in 89% and 96% from

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• photochromic derivatives with varying electronic and thus photochromic properties. The respective arylamines 13a–c were converted into their corresponding hydrazines 14a–c via diazonium-salt formation using sodium nitrite and subsequent reduction using tin(II) chloride [70]. The following nucleophilic

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

• alkene scope and exploring the site-selectivity in polyene substrates. General mechanism of alkene hydrofunctionalization via HAT. Reduction of the alkenyl chloride 1 by HAT. Substrate scope of alkyl-aryl azo compound synthesis via HAT. Conditions: alkene (0.250 mmol), diazonium salt (1.50 equiv), Co

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

•  20) [65]. The scope of the substrates demonstrated is quite broad, with substituted aromatic and aliphatic alkynes being used and a variety of substituents tolerated on the diazonium salt starting material. Terminal alkynes selectively formed 2-substituted benzothiophenes, whereas the