Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• superior electrophile in comparison to the ester function. Indeed, this bielectrophilic reagent reacted only at the nitro group, providing the amide 20 as the sole product. The yield was quite marginal, primarily due to decomposition of the fragile ester functionality under the harsh reaction conditions

Fluorine effect in nucleophilic fluorination at C4 of 1,6-anhydro-2,3-dideoxy-2,3-difluoro-β-D-hexopyranose

• Danny Lainé,
• Vincent Denavit,
• Olivier Lessard,
• Laurie Carrier,
• Charles-Émile Fecteau,
• Paul A. Johnson and
• Denis Giguère

Beilstein J. Org. Chem. 2020, 16, 2880–2887, doi:10.3762/bjoc.16.237

• 3 is the stereochemistry of the fluorine atom at C2. Finally, only decomposition originated from the use of mannose analogue 5 as substrate. The difference in terms of reactivity between 5 and 2 was unexpected since they only differ from the stereochemistry of the fluorine atom at C2 (distal to the

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

• David Liese,
• Hans Henning Wenk,
• Xin Lu,
• Jochen Kleinen and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2020, 16, 2820–2830, doi:10.3762/bjoc.16.232

• demonstrate the thermal reversibility of the gelation process. There are peak maxima at the heating and cooling phases that can be assigned to the formation of the gel structure and its decomposition. For the heating phase, a maximum was found at 45 °C, the endothermic melting process of the sample. In the

Easy access to a carbohydrate-based template for stimuli-responsive surfactants

• Thomas Holmstrøm,
• Daniel Raydan and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2020, 16, 2788–2794, doi:10.3762/bjoc.16.229

• mechanical impulse that can increase or decrease the distance between the two lipophilic tails, thus changing the amphiphilic properties of the molecule. Incorporating such molecules into the lipid bilayer of liposomes can result in the decomposition of the whole liposome when the stimuli-responsive

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand

• Matthias Hardy,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2020, 16, 2701–2708, doi:10.3762/bjoc.16.220

• weeks, while metalloligand 3 needs to be stored in an argon atmosphere at 3 °C and 1 even needs to be stored only in an argon atmosphere at −18 °C to prevent decomposition. The reduced stability of the amine precursors compared to cage 4 might be a result from the higher electron-donating capability of

Vicinal difluorination as a C=C surrogate: an analog of piperine with enhanced solubility, photostability, and acetylcholinesterase inhibitory activity

• Yuvixza Lizarme-Salas,
• Alexandra Daryl Ariawan,
• Ranjala Ratnayake,
• Hendrik Luesch,
• Angela Finch and
• Luke Hunter

Beilstein J. Org. Chem. 2020, 16, 2663–2670, doi:10.3762/bjoc.16.216

• described for 1 led to no detectable decomposition (Figure 3, Supporting Information File 1). Biological activity and solubility The biological activities of piperine (1) and the analog 2 were compared using two different assays, namely the inhibition of either acetylcholinesterase (AChE) or β-secretase

Synthesis of novel fluorinated building blocks via halofluorination and related reactions

• Attila Márió Remete,
• Tamás T. Novák,
• Melinda Nonn,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2020, 16, 2562–2575, doi:10.3762/bjoc.16.208

• decomposition upon reflux. In contrast, the treatment with trifluoroperacetic acid formed in situ in THF resulted in the expected allylic fluoride (rac)-33. Oxidative treatment under basic conditions, however, yielded the highly unsaturated diester (rac)-34, presumably via a base-promoted E1cB elimination of

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• decomposition products (Scheme 13). No reaction was observed using a 19 W CFL bulb in the absence of a PSCat. Despite acetophenone being a colorless oil with only trace absorption above 375 nm (an n–π* transition corresponding to a photon of 325 nm), it successfully functioned as a PSCat, undergoing

Synthesis of 6,13-difluoropentacene

• Matthias W. Tripp and
• Ulrich Koert

Beilstein J. Org. Chem. 2020, 16, 2136–2140, doi:10.3762/bjoc.16.181

• without noticeable decomposition. However, in solution under ambient atmosphere and sunlight decomposition takes place quickly, which is indicated by decolorization of a purple solution in CH2Cl2 within 3 min. 1H NMR analysis showed 6,13-pentacenequinone (15) as the degradation product. The rate of

• -difluoroanthracene. This strategy could be applicable for the synthesis of differently substituted 6,13-difluoropentacenes as well. Structures of pentacene and fluorinated pentacenes. UV–vis spectrum of F2PEN 5 in CH2Cl2. Retrosynthetic analysis of F2PEN 5. Synthesis of F2PEN 5. Decomposition of diol 13 in solution

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• the Suzuki cross-coupling reaction published for a similar system [30], decomposition products and only 25% yield were obtained. Optimization by lowering the reaction temperature increased the yield to 91% (Scheme 1). Switching properties of porphyrin 1 Preliminary investigations on the photochemical

• , the switching efficiency slowly decreased over 100 switching cycles to ≈80% of the original value (see Supporting Information File 1, Figure S4). A thermal decomposition at 40 °C in THF was observed by a color change from red to green. Hence, the catalytic experiments were limited to 25 °C. At last

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• (Table 2). The obvious consequence being a decrease in the substrate conversion. This, however, could be compensated to some extent by longer reaction times. Based on this observation catalyst decomposition appeared to be negligible and it seemed, that the role of gold is primarily that of a Lewis acid

• (first line solvent chlorobenzene, second line solvent anisole: catalyst loading, reaction time, conversion % (isolated yield %), reaction temperature 60 °C). aPartial decomposition during column chromatography observed. Hydrohydrazidation of internal alkynes in chlorobenzene and anisole using complex 1

Convenient access to pyrrolidin-3-ylphosphonic acids and tetrahydro-2H-pyran-3-ylphosphonates with multiple contiguous stereocenters from nonracemic adducts of a Ni(II)-catalyzed Michael reaction

• Alexander N. Reznikov,
• Dmitry S. Nikerov,
• Anastasiya E. Sibiryakova,
• Victor B. Rybakov,
• Evgeniy V. Golovin and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2020, 16, 2073–2079, doi:10.3762/bjoc.16.174

• . The formylated product 10a may be purified by chromatography without decomposition. Subsequent acid hydrolysis of compound 10a leads to pyrrolidinylphosphonic acid hydrochloride 11a (Scheme 2). Similarly, pyrrolidinylphosphonic acids 11b–d were obtained from the corresponding phosphonates 6b,c,e

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• (4), FR901464 (1) [15][16], spliceostatin E (10) [41], and thailanstatin A methyl ester (123) [31] used the cross-metathesis strategy for the coupling of the diene 49 with 85, 115, and 102, respectively (Scheme 21). In order to avoid the decomposition problems encountered by Koide, the mixed cyclic

On the hydrolysis of diethyl 2-(perfluorophenyl)malonate

• Ilya V. Taydakov and
• Mikhail A. Kiskin

Beilstein J. Org. Chem. 2020, 16, 1863–1868, doi:10.3762/bjoc.16.153

• starting ester remained intact, while under drastic conditions (high concentration of alkali, homogeneous solutions, elevated temperatures), decomposition and/or decarboxylation occurred. However, it is possible that decarboxylation took place during the isolation of the free acid. In all cases, no desired

• malonic acid 2 was isolated from the reaction mixtures; the main part of the original material was recovered. In some experiments, variable amounts of 2-(perfluorophenyl)acetic acid (12) were obtained after acidification of the basic solution. Moreover, noticeable decomposition of 3 was observed along

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• amine/base with DMSO as an activator. Potassium ethylxanthate [64][65] and sodium sulfide as a sulfur sources in the presence of Et3N in DMSO (Table 1, entries 8 and 9) also did not furnish the desired product 2bA. A decomposition of the product was observed in the case of Na2S. Interestingly, the

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• . Condensation with 2-amino-2-methylpropan-1-ol and oxidation with NBS yielded oxazoline 6 in a good yield. Directed ortho-metalation utilizing TMPMgCl·LiCl under mild conditions and subsequent smooth formylation with DMF afforded benzaldehyde 7 (see Scheme 2). Due to rapid decomposition of 7 under ambient and

• reduction with NaBH4 to give the primary alcohol 19. In contrast to benzaldehyde 7, carbaldehyde 18 showed no decomposition at ambient temperature. While acidic hydrolysis of 19 provided exocyclic γ-lactone 20, the substitution reaction with DPPA/NaN3 yielded the primary azide in 87% yield. In accordance to

• fluorene showed such a high reactivity that rapid decomposition occurred. However, bromination was conducted by various substitution methods delivering benzyl bromide 24, which upon isolation cyclized to iminium bromide 25 in high yield. To suppress this unexpected cyclization, careful fine-adjustment of

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

• photocatalytic decomposition of water on illuminated titanium dioxide (TiO2) electrodes in 1972 [27]. This critical report began the field of semiconductor HPC, and in combination with the development of organic electronics, established fundamental principles that still underpin much of the cutting-edge

• irradiated with sunlight [74]. The use of titania as a pigment had been practiced for centuries, and the observation that TiO2-based surface coatings exposed to sunlight irradiation would “chalk” (the formation of a loose white powder on the paint surface) had been recognised as the decomposition of organic

One-pot synthesis of 1,3,5-triazine-2,4-dithione derivatives via three-component reactions

• Gui-Feng Kang and
• Gang Zhang

Beilstein J. Org. Chem. 2020, 16, 1447–1455, doi:10.3762/bjoc.16.120

• intermediate 4 led to a decomposition. In another experiment, the same reaction was tested at 80 °C for 1 h and intermediate 4 in addition to formylthiourea (5) were formed in low yields (Table 1, entry 7). When the reaction time was extended to 5 h, the desired three component product 6-(methylthio)-4-phenyl

The McKenna reaction – avoiding side reactions in phosphonate deprotection

• Katarzyna Justyna,
• Joanna Małolepsza,
• Damian Kusy,
• Waldemar Maniukiewicz and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 1436–1446, doi:10.3762/bjoc.16.119

• be accompanied by side reactions such as the cleavage of tert-butyl carboxyester, [14][15] or other ester groups [16], as well as the formation of decomposition products [17][18][19][20]. Instead of focusing only on the experiments that “did work”, we decided to follow an alternative strategy

• from the reaction mixture by washing with aqueous sodium carbonate solution. The model compounds used for this study (in red: the functionality of the molecules vulnerable to side reactions). Schematic overview of the McKenna reaction including the decomposition of BTMS in protic solvents. The desired

Disposable cartridge concept for the on-demand synthesis of turbo Grignards, Knochel–Hauser amides, and magnesium alkoxides

• Mateo Berton,
• Kevin Sheehan,
• Andrea Adamo and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2020, 16, 1343–1356, doi:10.3762/bjoc.16.115

• magnesium turnings [31]; (2) the formation of undesired side products by thermal decomposition and exothermic reactions not suitable for industrial processes [32]; (3) the activation of a metallic surface is required and can introduce safety issues due to the high reactivity of the activated metal. Flow

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• materials, which were accompanied by a decomposition residue. In contrast, maleimides 7b and 7c reacted efficiently to furnish the respective endo/exo adducts 9a–d/10a–d in good to high endo diastereoselectivity and yields (Table 2, entries 1–4). The cycloaddition with 7c led to the best selectivity (vide

Ferrocenyl-substituted tetrahydrothiophenes via formal [3 + 2]-cycloaddition reactions of ferrocenyl thioketones with donor–acceptor cyclopropanes

• Grzegorz Mlostoń,
• Mateusz Kowalczyk,
• André U. Augustin,
• Peter G. Jones and
• Daniel B. Werz

Beilstein J. Org. Chem. 2020, 16, 1288–1295, doi:10.3762/bjoc.16.109

• of crude mixtures by a short-column chromatography was necessary to remove traces of iron particles formed as a side product after partial decomposition of ferrocenyl containing substrates and/or products formed under reaction conditions. Dimethyl 2-ferrocenyl-2,5-diphenyltetrahydrothiophene-3,3

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• the decomposition of iminoxyl radicals 2 generated from oximes 1 under the action of Ag2O [53] were studied by K. U. Ingold et al. (Figure 2). In most cases, the reaction was accompanied by the release of N2 and N2O, as well as the corresponding carbonyl compounds (3a–c). Dimerization of iminoxyl

• corresponding to the free iminoxyl radical, which indicates the reversibility of dimerization [53]. During the oxidation of pivalic aldoxime 1e by Ag2O, the formation of nitrile oxide 6e was observed, which then slowly dimerized to the corresponding furoxan 7e. The kinetics of the decomposition of dialkyl

• , arylalkyl, and diaryl oxime radicals was also studied by EPR spectroscopy [53]. Radicals were generated under inert atmosphere directly in the EPR cavity by photolysis of the added di-tert-butyl peroxide (Scheme 1). The authors pointed out the complexity of the processes of iminoxyl radicals’ decomposition

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• . Poly(propiolate) salts are formed by polymerization of the starting materials after heating. The different cations of the propiolates cause changes in the thermal behavior of the starting materials since different temperatures are required for the decomposition or different amounts of gases are

• starting materials. The thermal decomposition behavior of the precursors, and thus the resulting morphology of the carbon materials is influenced by the propiolate cations [80]. Spherical carbons The preparation of spherical mesoporous carbon particles as catalyst support with high surface areas

• about 1700 cm−1 was found due to the decomposition of the oxygen-containing surface groups at higher treatment temperatures [115]. The group of Moreno-Castilla investigated the treatment with oxidizing agents (H2O2 or HNO3) or activating reagents by FTIR. They found that the amount of oxygen fixed on

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• decomposition [69][70], these species are straightforward to synthesize and can be easily reduced (Ered ≈ −0.1 V to −0.3 V) [71][72]. This makes them valuable electron acceptors for photocatalytic strategies. The SET reduction results in the generation of an aryl radical upon the irreversible loss of N2 as the