Structure and thermal stability of phosphorus-iodonium ylids

• Andrew Greener,
• Stephen P. Argent,
• Coby J. Clarke and
• Miriam L. O’Duill

Beilstein J. Org. Chem. 2024, 20, 2931–2939, doi:10.3762/bjoc.20.245

• and potential decomposition pathways will enable the future design and development of new reagents. Keywords: hypervalent iodine; reagent development; structural analysis; thermal stability; thermogravimetric analysis; Introduction Hypervalent iodine(III) reagents have experienced a renaissance in

• groups or delocalisation into a π-system results in crystalline, bench-stable reagents. In the absence of stabilising factors, rapid decomposition occurs [21][22][23]. In this study, we aim to gain a fundamental understanding of the factors that stabilise phosphorus-iodonium ylids 1 (Figure 1B) [24][25

• File 1.) All compounds show a multi-step mass loss behaviour with a range of TGA decomposition onset temperatures (Tonset) between 107–137 °C, with the exception of three compounds that are stable to higher temperatures (1a: Tonset = 176 °C, ΔH = 134 J/g; 1j: 172 °C, 130 J/g; 2: 225 °C, 274 J/g; Table

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

• of n-propyl mercaptane with subsequent addition of acetic anhydride, pyridine and KHF2 afforded indigo-N-rhamnoside 5c as a 2:1 mixture of α/β-anomers. The relatively low yield is a result of side reactions and decomposition, due to the rather unstable nature of the product. The reaction of 5c with

• failed under various conditions, due to decomposition by retro-aldol reaction. Interestingly, while indirubin-N-glycosides 17, thio- and selenoindirubin-N-glycosides 33 and 38 were formed as pure Z-isomers, oxoindirubin-N-glycosides 41 were formed as mixtures of E- and Z-isomers. The isolated yields of Z

•  42) [60]. Despite the absence of a lactone moiety, deprotection proved to be unsuccessful, due to decomposition. Miscelleaneous 6H-Indolo-[2,3-b]quinoxaline-N-glycosides The cyclization of isatin-N-rhamnoside β-16a with 1,2-diaminobenzene (79a) afforded 6H-indolo-[2,3-b]quinoxaline-N-glycoside β-80a

C–C Coupling in sterically demanding porphyrin environments

• Liam Cribbin,
• Brendan Twamley,
• Nicolae Buga,
• John E. O’ Brien,
• Raphael Bühler,
• Roland A. Fischer and
• Mathias O. Senge

Beilstein J. Org. Chem. 2024, 20, 2784–2798, doi:10.3762/bjoc.20.234

• structural decomposition (NSD) method developed by Shelnutt and co-workers [9] and further implemented and visualized by us [8][10]. Of the four main quantifiable distortion modes, saddle-shaped porphyrins can be afforded by peri-interactions between β-substituents and the meso-substituents [3][11], or

Synthesis of spiroindolenines through a one-pot multistep process mediated by visible light

• Francesco Gambuti,
• Jacopo Pizzorno,
• Chiara Lambruschini,
• Renata Riva and
• Lisa Moni

Beilstein J. Org. Chem. 2024, 20, 2722–2731, doi:10.3762/bjoc.20.230

• . Thus, we supposed that the second visible light-mediated oxidation properly occurred generating the iminium ion which underwent decomposition. Even using 3-(N,N-dimethylamino)aniline, the corresponding spiro compound 3l was not obtained. In this case, it is assumed that the highly acidic environment of

Synthesis of benzo[f]quinazoline-1,3(2H,4H)-diones

• Ruben Manuel Figueira de Abreu,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2708–2719, doi:10.3762/bjoc.20.228

• respective cyclisation product. Hence, the application of the reaction conditions to starting materials 4b, 4c and 4e resulted in the decomposition of the starting materials and no product could be isolated. The employment of heterocyclic benzothiophene gave a very good yield of 80% for product 5i. Optical

Efficient modification of peroxydisulfate oxidation reactions of nitrogen-containing heterocycles 6-methyluracil and pyridine

• Alfiya R. Gimadieva,
• Yuliya Z. Khazimullina,
• Aigiza A. Gilimkhanova and
• Akhat G. Mustafin

Beilstein J. Org. Chem. 2024, 20, 2599–2607, doi:10.3762/bjoc.20.219

• − ion, which is formed by the non-radical decomposition of the peroxydisulfate ion in a strongly alkaline medium [34]: The Elbs and Boyland–Sims reactions were also effectively modified by the use of H2O2 as a co-oxidant (binary oxidation mixture APS/H2O2). Adding 2.0–2.3 equiv of H2O2 (Table 3) [35

• peroxydisulfate ion, leading to the production of oxygen [39]: Oxygen accumulation is additionally achieved by hydrogen peroxide self-decay, which is known to be increased in alkaline conditions [40]: Additionally, it has been reported [41] that hydroxyl radicals, produced from the decomposition of H2O2, can

Transition-metal-free synthesis of arylboronates via thermal generation of aryl radicals from triarylbismuthines in air

• Yuki Yamamoto,
• Yuki Konakazawa,
• Kohsuke Fujiwara and
• Akiya Ogawa

Beilstein J. Org. Chem. 2024, 20, 2577–2584, doi:10.3762/bjoc.20.216

• somewhat difficult due to strong adsorption or decomposition on silica gel. Since some arylboronates are somewhat unstable, it is desirable to synthesize such compounds and then use them in a one-pot manner for the following reactions without isolation. To gain insight into the reaction pathways, several

•  1) was analyzed by 11B NMR measurement. It was noteworthy that diboron 2 was reactive with air under the reaction conditions, and the decomposition of 2 to form pinB–O–Bpin and pinB–OH was confirmed. The decomposition was also occurred by heating the solution of diboron 2 in BTF in air; however, in

• the presence of TEMPO, the decomposition of 2 was sightly occurred, and almost all of 2 was recovered (see Supporting Information File 1). Based on the results, diboron 2 could also be activated via the thermal homolysis of the B–B bond in the presence of oxygen (air). Based on the results of the

Anion-dependent ion-pairing assemblies of triazatriangulenium cation that interferes with stacking structures

• Yohei Haketa,
• Takuma Matsuda and
• Hiromitsu Maeda

Beilstein J. Org. Chem. 2024, 20, 2567–2576, doi:10.3762/bjoc.20.215

• S19 in Supporting Information File 1). Theoretically performed energy decomposition analysis (EDA) based on FMO2-MP2 using the basis set of NOSeC-V-DZP with MCP [37][38][39][40] for the anion and closely located 2+, as suggested by Hirshfeld surface analysis, revealed that short counteranion–TATA

Facile preparation of fluorine-containing 2,3-epoxypropanoates and their epoxy ring-opening reactions with various nucleophiles

• Yutaro Miyashita,
• Sae Someya,
• Tomoko Kawasaki-Takasuka,
• Tomohiro Agou and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2024, 20, 2421–2433, doi:10.3762/bjoc.20.206

• ). The subjection of the compounds 1h and 1i to the standard conditions described above resulted in high recovery of the substrates, which could be explained by their higher LUMO + 1 energy levels responsible for the epoxidation [43]. Extensive decomposition was observed in the case of 1j even in a

Evaluating the halogen bonding strength of a iodoloisoxazolium(III) salt

• Dominik L. Reinhard,
• Anna Schmidt,
• Marc Sons,
• Julian Wolf,
• Elric Engelage and
• Stefan M. Huber

Beilstein J. Org. Chem. 2024, 20, 2401–2407, doi:10.3762/bjoc.20.204

• ]. For all catalyst systems, decomposition of the −BArF24 anion was observed via 1H and 19F NMR spectroscopy, which is known to happen in the presence of activated gold complexes [29]. The stability of the DAI cations was checked with 1H NMR: the characteristic doublets belonging to the respective

• iodonium structures 1+, 2+, 3+, and 7+ were found to be constant (see Supporting Information File 1). The signals of the iodoxinium cation 4+ were overlapping with signals of the anion. However, the stability of 4+ (as well as of 2+) could be confirmed by 19F NMR measurements: no decomposition of the

Tandem diazotization/cyclization approach for the synthesis of a fused 1,2,3-triazinone-furazan/furoxan heterocyclic system

• Yuri A. Sidunets,
• Valeriya G. Melekhina and
• Leonid L. Fershtat

Beilstein J. Org. Chem. 2024, 20, 2342–2348, doi:10.3762/bjoc.20.200

• obtained using NaNO2 in an AcOH + MeSO3H [1:1] solution (Table 1, entry 7). Organic solvents (CH2Cl2, MeCN) were not applied due to a known rapid decomposition of the generated (1,2,5-oxadiazolyl)diazonium salts [42]. The optimized conditions were applied for the preparation of [1,2,5]oxadiazolo[3,4-d

Hydrogen-bond activation enables aziridination of unactivated olefins with simple iminoiodinanes

• Phong Thai,
• Lauv Patel,
• Diyasha Manna and
• David C. Powers

Beilstein J. Org. Chem. 2024, 20, 2305–2312, doi:10.3762/bjoc.20.197

• with the stability of the relevant iminoiodinane reagent, with higher yields attributed to more electron-rich sulfonamide substitution such as 2a. Relatively electron-deficient iminoiodinanes are less efficient but are also more prone to decomposition (see Supporting Information File 1, Figure S2 for

• challenging iminoiodinanes). In situ preparation of the iminoiodinane intermediates is possible, and for those reagents that undergo facile decomposition, aziridination is more efficient using these conditions (yields for in situ-generated iminoiodinanes are in parentheses in Scheme 3, with N-o-methyl (6g

Catalysing (organo-)catalysis: Trends in the application of machine learning to enantioselective organocatalysis

• Stefan P. Schmid,
• Leon Schlosser,
• Frank Glorius and
• Kjell Jorner

Beilstein J. Org. Chem. 2024, 20, 2280–2304, doi:10.3762/bjoc.20.196

• [96] investigated a bromocyclization catalysed by a chiral phosphoric acid (CPA) and a DABCOnium brominating reagent (Figure 6). The authors calculated transition state conformer ensembles for several flexible DABCOnium systems and performed energy decomposition analysis to separate the interactions

Synthesis and reactivity of the di(9-anthryl)methyl radical

• Tomohiko Nishiuchi,
• Kazuma Takahashi,
• Yuta Makihara and
• Takashi Kubo

Beilstein J. Org. Chem. 2024, 20, 2254–2260, doi:10.3762/bjoc.20.193

• dimerization in solution, the radical still remains even at 190 K due to the bulky nature of the two anthryl groups. Interestingly, upon exposure to air, the purple color of the radical solution quickly fades to orange, resulting in decomposition to give 9-anthryl aldehyde and anthroxyl radical derivatives

• radical. The unpaired electron is primarily located at the central sp2 carbon, a highly reactive site. The DAntM radical readily reacts with oxygen, leading to 1,2-dioxetane intermediate and decomposition to give anthryl aldehyde and a stable anthroxyl radical. Results and Discussion The synthetic route

• , indicating that the high reactivity of the central sp2 carbon. To evaluate the decomposition pathway, the decomposed materials were characterized. Surprisingly, the major compound detected by 1H NMR measurement of the crude material was compound 1, along with di(10-mesityl-9-anthryl)methane (4) as a minor

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• aware of resource recycling, and promote the use of natural energy [16]. The following three methods are generally used to generate heteroatom radicals (E•) (Scheme 1). In method 1, E• is generated by hydrogen abstraction from E–H by cyanoisopropyl radicals generated by thermal decomposition of 2,2

• a pioneering study, Ito and Saegusa et al. reported the radical addition of thiols to isocyanides (Scheme 2) [27]. Thermal decomposition of AIBN as a radical initiator generates the 2-cyano-2-propyl radical ((NC)(CH3)2C•), which abstracts hydrogen from the thiol (R’SH) to form the thiyl radical (R’S

• yields the sequential addition products 9 in moderate to excellent yields (Scheme 5) [33]. The product can be used as a precursor for the carbapenem scaffold, one of the basic scaffolds of antibiotics. Thermal or photoirradiated decomposition of organotellurium compounds generates carbon radicals that

Development of a flow photochemical process for a π-Lewis acidic metal-catalyzed cyclization/radical addition sequence: in situ-generated 2-benzopyrylium as photoredox catalyst and reactive intermediate

• Masahiro Terada,
• Zen Iwasaki,
• Ryohei Yazaki,
• Shigenobu Umemiya and
• Jun Kikuchi

Beilstein J. Org. Chem. 2024, 20, 1973–1980, doi:10.3762/bjoc.20.173

• continues to flow and the reaction can be quenched immediately when necessary, the decomposition of an unstable product under the reaction conditions can be avoided [22][23][24][25]. Furthermore, when a photoreaction is performed in a flow system, there is an advantage that the light irradiation efficiency

Access to 2-oxoazetidine-3-carboxylic acid derivatives via thermal microwave-assisted Wolff rearrangement of 3-diazotetramic acids in the presence of nucleophiles

• Ivan Lyutin,
• Vasilisa Krivovicheva,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 1894–1899, doi:10.3762/bjoc.20.164

• -oxoazetidine-3-carboxylic acid derivatives based on the thermally promoted Wolff rearrangement of diazotetramic acids. Results and Discussion Diazotetramic acid derivatives 1 are available in a wide variety using the techniques described previously [32]. The conditions for their thermal decomposition were

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

Oxidative fluorination with Selectfluor: A convenient procedure for preparing hypervalent iodine(V) fluorides

• Samuel M. G. Dearman,
• Xiang Li,
• Yang Li,
• Kuldip Singh and
• Alison M. Stuart

Beilstein J. Org. Chem. 2024, 20, 1785–1793, doi:10.3762/bjoc.20.157

• iodine(I) precursor 8 (Table 1). Reacting 8 with 4 equivalents of trichloroisocyanuric acid (TCCA) and 6 equivalents of potassium fluoride in dry acetonitrile at 40 °C for 48 hours formed difluoroiodane 6 in a 90% spectroscopic yield (Table 1, entry 1). An iodosyl decomposition product 9 was also formed

• fluorinating reagent (Table 1, entry 5). When 8 was reacted with 4 equivalents of freeze-dried Selectfluor in dry acetonitrile at 40 °C for 48 hours, difluoroiodane 6 was formed in 85% spectroscopic yield. However, the iodosyl decomposition product 9 was also produced in 15% spectroscopic yield, despite

• rate of decomposition was reduced significantly (green line in Figure 3). The hydrolysis of the four hypervalent iodine(V) fluorides was also investigated in acetonitrile-d3 by adding 5 equivalents of water. All four compounds decomposed to their corresponding iodosyl compounds and the order of

A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• kinetic model describing the components and the non-negativity constraint on the absorbance, can help to guide the decomposition of the data into chemically meaningful concentration traces and species-associated spectra (SAS) [38]. Global and target analysis is one of the methods employed in recent

Oxidation of benzylic alcohols to carbonyls using N-heterocyclic stabilized λ³-iodanes

• Thomas J. Kuczmera,
• Pim Puylaert and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 1677–1683, doi:10.3762/bjoc.20.149

• decomposition for thiophenylmethanol 3y. Regarding the reaction mechanism, two plausible pathways can be discussed based on literature examples (Scheme 1, path a [17] and path b [33]). In either path, initial ligand exchange to the hydroxy(chloro)iodane I-OH is proposed. For getting an indication of a chloride

New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

• Fátima C. Teixeira,
• António P. S. Teixeira and
• C. M. Rangel

Beilstein J. Org. Chem. 2024, 20, 1623–1634, doi:10.3762/bjoc.20.145

• , purification of the crude product by column chromatography led to the decomposition of compound TP7. Another strategy was devised to obtain the desired triazinephosphonate TP7: The first step was the nucleophilic substitution of the chlorine atoms of triazine 1 by 4-hydroxybenzaldehyde (12), followed by the

Regio- and stereochemical stability induced by anomeric and gauche effects in difluorinated pyrrolidines

• Ana Flávia Candida Silva,
• Francisco A. Martins and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2024, 20, 1572–1579, doi:10.3762/bjoc.20.140

• both C–F bonds in 17 and 19 enabled an additional σCH→σ*CF interaction, rather than the negligible σCF→σ*CF electron delocalization that would occur if these bonds were vicinally antiperiplanar. As discerned from the decomposition of the full electronic energy into Lewis (e.g., steric effects) and non

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor

• Koichi Mitsudo,
• Atsushi Osaki,
• Haruka Inoue,
• Eisuke Sato,
• Naoki Shida,
• Mahito Atobe and
• Seiji Suga

Beilstein J. Org. Chem. 2024, 20, 1560–1571, doi:10.3762/bjoc.20.139

• decomposition of the substrates, and the desired products were not obtained. This system can be applied to large-scale syntheses. A similar yield of 7a was obtained when the reaction was scaled up (Scheme 5a). The electrolysis of 2.32 g of 6a gave 2.12 g of 7a (88% yield). Next, we examined the electroreduction

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• fragility of secondary and tertiary benzyl fluorides, as they observe elimination and hydrolysis in many cases [20][100], thereby raising question marks over their suitability as synthetic targets. Monofluorinated methyl arenes, however, are much more stable to these decomposition pathways. The nucleophilic

• -oxidation and decomposition to improve the reaction efficiency overall. Conclusion The fluorination of benzylic C(sp3)–H bonds provides rapid access to an important functional group used in medicinal chemistry to control the pharmacokinetic profile of drug candidates. Historical and recent research efforts