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

• , resulting from HBr addition to the triple bond. The presence of these products was confirmed by 1H NMR analysis [signals at δ 5.56 and δ 5.85 ppm representing protons in 16 (CBr=CH2) and multiplets at δ 6.29 and 6.33 ppm representing protons in 17 (CH=CHBr)]. In order to identify the factor(s) responsible

Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions

• Xiaoming Ma,
• Suzhi Meng,
• Xiaofeng Zhang,
• Qiang Zhang,
• Shenghu Yan,
• Yue Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2020, 16, 1225–1233, doi:10.3762/bjoc.16.106

• hexahydropyrrolo[2,1-a]isoquinoline compounds 9a–o in moderate to good yields as a single isomers which were confirmed by 1H NMR analysis of the crude reaction mixtures. The substitution groups R3 (Me, Et, Ph, Bn, c-C6H11) on maleimide have no significant influence on the product yields to afford 9a–f in 73–80

Accelerating fragment-based library generation by coupling high-performance photoreactors with benchtop analysis

• Quentin Lefebvre,
• Christophe Salomé and
• Thomas C. Fessard

Beilstein J. Org. Chem. 2020, 16, 982–988, doi:10.3762/bjoc.16.87

• ). Out of the 15 reactions showing product formation by TLC–MS, 7 gave the product in sufficient purity after one round of purification, while 8 were contaminated with solvent impurities, or obtained in too low yields for appropriate NMR analysis. Fourteen did not give the expected product, often showing

Diversity-oriented synthesis of 17-spirosteroids

• Benjamin Laroche,
• Thomas Bouvarel,
• Martin Louis-Sylvestre and
• Bastien Nay

Beilstein J. Org. Chem. 2020, 16, 880–887, doi:10.3762/bjoc.16.79

• structure and stereochemistry of the products were determined by 2D NMR analysis. Taking 16b as an example, the key NOESY correlations between proton H-4' at 2.79 ppm and steroid protons H-12 at 1.33/1.65 ppm demonstrated that H-4' is on the α-face of the cyclohexene (Figure 3a). The endo character of the

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• the bisbenzylated side product 21a. According to NMR analysis (COSY, HSQC and HMBC, see Supporting Information File 1), this second benzyl group was attached to position 7 of the THIQ scaffold. Additionally, the effect of different substituents on the THIQ core was investigated. A fluoro substituent

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

• Ji Ma,
• Yubin Fu,
• Junzhi Liu and
• Xinliang Feng

Beilstein J. Org. Chem. 2020, 16, 791–797, doi:10.3762/bjoc.16.72

• annulation was favorable for the formation of six-membered rings. Nevertheless, the existence of several rotamers of 1 derived from the restricted rotation of the peripheral phenyl ring substituents and its nonplanar geometry prevented the structure elucidation by proton NMR analysis [35]. Single crystals of

Asymmetric synthesis of CF₂-functionalized aziridines by combined strong Brønsted acid catalysis

• Xing-Fa Tan,
• Fa-Guang Zhang and
• Jun-An Ma

Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60

• ) were added and the mixture was reacted at rt for 24 hours unless otherwise annotated. The yields are those of isolated products, and the dr was determined by 19F NMR analysis of the crude mixture. The results in parentheses are those of isolated products after the dissolution–filtration process: The

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• Information File 1, Figure S7) and δ 6.57 and 7.63 ppm with a J value of 15 Hz for compound 18 (Supporting Information File 1, Figure S9) as inferred by 1H NMR analysis. The resulting Suzuki-coupled products 16 and 18, were subjected to benzylic oxidation expecting the olefin functionality would facilitate

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• comparative NMR analysis and mass spectrometry (see Supporting Information File 1). Optical properties The α- and β-ethynyl-substituted BODIPYs exhibit large bathochromic shifts in the absorption and fluorescence spectra relative to the unsubstituted 1a with extended π-conjugation (Figure 4 and Figure 5). The

Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands

• Shohei Mimura,
• Sho Mizushima,
• Yohei Shimizu and
• Masaya Sawamura

Beilstein J. Org. Chem. 2020, 16, 537–543, doi:10.3762/bjoc.16.50

• diethoxymethylsilane (4 equiv) as a reductant and t-AmOH (1 equiv) as a protonation reagent in DMA as the solvent at 25 °C for 15 h, the product 2a was produced in 98% yield (1H NMR analysis) with a promising enantioselectivity of 69% ee (Table 1, entry 1). When the phenolic hydroxy group of L1 was changed to a

• % by 1H NMR analysis with 1,1,2,2-tetrachloroethane as an internal standard. After a rough purification of the crude product by silica gel chromatography (eluent: 0 to 1% EtOAc/hexane), the collected residue was further purified by GPC (eluent: CHCl3) to afford the pure product 2a as colorless oil

Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons

• Goki Hirata,
• Yu Yamane,
• Naoya Tsubaki,
• Reina Hara and
• Takashi Nishikata

Beilstein J. Org. Chem. 2020, 16, 502–508, doi:10.3762/bjoc.16.45

• determined by 1H NMR analysis. Substrate scope of 2 and 4. aConducted at 100 °C for 20 h in 1,4-dioxane with CuI (10 mol %), 1,10-Phen (10 mol %), Cy2NMe (1.0 equiv), 2 (1.0 equiv) and 4 (3.0 equiv). Yields were determined by 1H NMR analysis. bIncluding E and Z isomers. Reaction modes of alkyne. Proposed

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

Formal preparation of regioregular and alternating thiophene–thiophene copolymers bearing different substituents

• Atsunori Mori,
• Keisuke Fujita,
• Chihiro Kubota,
• Toyoko Suzuki,
• Kentaro Okano,
• Takuya Matsumoto,
• Takashi Nishino and
• Masaki Horie

Beilstein J. Org. Chem. 2020, 16, 317–324, doi:10.3762/bjoc.16.31

• (10 mL) to form a precipitate, which was filtered off to leave a dark purple solid. After washing with methanol and hexanes repeatedly, the solid was dried under reduced pressure to afford 79.6 mg of 6b (84% isolated yield). The HT regioregularity was confirmed by 1H NMR analysis, and the molecular

Ultrasonic-assisted unusual four-component synthesis of 7-azolylamino-4,5,6,7-tetrahydroazolo[1,5-a]pyrimidines

• Yana I. Sakhno,
• Maryna V. Murlykina,
• Oleksandr I. Zbruyev,
• Anton V. Kozyryev,
• Svetlana V. Shishkina,
• Dmytro Sysoiev,
• Vladimir I. Musatov,
• Sergey M. Desenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2020, 16, 281–289, doi:10.3762/bjoc.16.27

• . However, the reaction time had to be increased to 24 h, and the yields and purity of the compounds 4 decreased (as seen via TLC and NMR analysis), obviously due to the worse homogenization and mass transfer compared to ultrasonication. Literature data [17][26][27][33][34][35] indicates that 5

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

• Katarzyna Włodarczyk,
• Piotr Borowski and
• Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

• . Interestingly, compound 18 underwent isobutene elimination rather than rearrangement under the reaction conditions, whereas compound 19 led to the formation of a mixture of three products, with alkenylphosphine sulfide 35 being the major compound. The structures were assigned based on NMR analysis as all

• compounds failed to give single crystals for X-ray analysis. The presence of an oxygen atom attached to the phosphorus atom in the products could be deduced based on 1H and 13C NMR analysis. In the 1H NMR spectra of phosphine sulfide 12, the chemical shifts of the signals belonging to the aromatic protons

• signals were found at 41.2 ppm/11.0 Hz and 41.6 ppm/10.7 Hz, respectively. The shifts indicated the presence of a C–S and not a C–O bond in the carbon skeleton [64][65], and the coupling constant value was typical for an γ-carbon atom present in a phosphine derivative [67][68][69]. In this regard, 31P NMR

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• was tested. The structure of compound 6 was confirmed by NMR analysis. The HMBC spectrum of 6 showed downfield shift of the atom H-4. Hydrogen H-7 illustrated a correlation separated by three bonds with atom C-2, like that with hydrogens H-4 and H-6 (Figure 2b). Furthermore, the C-1 and C-5 positions

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• by the decrease of the π–π* absorption in the range 330-440 nm and the increase of the n–π* absorption above 440 nm (Figure 3), equally observed for 1fE to 1fZ (Figure S1 in Supporting Information File 1). The NMR analysis of photoirradiated samples of macrocyles 1 showed that the photostationary

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• microwave reactor for 30–60 min, with product formation assessed by high field NMR analysis. Under these reaction conditions, m,p'-quaterphenyl is the equilibrium product. This isomer is unchanged by the reaction conditions and all other quaterphenyl isomers rearrange to m,p' as the dominant or sole product

• assessed by high field NMR analysis. Under these reaction conditions, m,p'-quaterphenyl (13) is the equilibrium product. This isomer is unchanged by the reaction conditions and all other quaterphenyl isomers rearrange to m,p' as the dominant or sole product. DFT computations with inclusion of implicit

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• around the iron centre is viewed linear with an angle of 178.11(3)°. The paramagnetic nature of the oxidized ferrocenophane 4 can also be verified using 1H NMR analysis. While the signals for the CH2 groups of the carbon bridge occur as a multiplet at 1.37–1.29 ppm as well as a triplet at 0.90 ppm, the

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• 29 (31P NMR: ROPPh2 δ = 107 ppm), respectively (Scheme 6). Attempts to carry out a sigmatropic rearrangement in toluene at 100 ºC as well as in xylene at 140 ºC failed. The formation of the phosphine oxide products was not observed by 31P NMR analysis. The probable reason for the lack of the

• chromatography on silica gel. For the purpose of this study, (1R,4R,5R)-apopinenol (16) was subjected to the Mitsunobu reaction to obtain the product with inverted configuration at C4. Alcohol 16 was reacted with diisopropyl azodicarboxylate, triphenylphosphine, and p-nitrobenzoic acid in THF [30]. 1H NMR

• analysis of the crude p-nitrobenzoate 17 revealed a mixture of the predicted p-nitrobenzoate of apopinenol 18 together with an ester of 16 in a ratio of 79:21. Attempts to separate p-nitrobenzoates of 18 and 16 by column chromatography on silica gel failed. The mixture of esters, after purification, was

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• optimization procedures (Scheme 2). The overall yield of the isolated epimers was 92%. According to Binder et al. [17] and our own experience [18], we expected the syn-product (2-syn) to be the main diastereomer. However, the determination of the configuration is not possible by NMR analysis. Consequently, the

• -acetylation was conducted leading to a mixture of all four species, indicated by NMR analysis (Scheme 3). In the case of 2-syn the β-pyranose species 5-syn-β was obtained as the main product, besides α-pyranose (5-syn-α) as well as both anomers of the furanoid form (Scheme 4). The overall yield obtained over

• main product turned out to adopt the β-pyranoid form, 5-syn-β and 5-anti-β, respectively, determined by thorough NMR analysis, in an overall yield of 40% and 42% over three steps calculated from epimers 2-syn and 2-anti, respectively. This work demonstrates the indium-mediated allylation reaction to be

Isolation of fungi using the diffusion chamber device FIND technology

• Benjamin Libor,
• Henrik Harms,
• Stefan Kehraus,
• Ekaterina Egereva,
• Max Crüsemann and
• Gabriele M. König

Beilstein J. Org. Chem. 2019, 15, 2191–2203, doi:10.3762/bjoc.15.216

• genus. From the solid, sea-salt containing cultures of H. cf. alpina the ethyl acetate soluble organic compounds were analysed. A first fractionation was achieved by vacuum liquid chromatography (VLC) on reversed-phase material yielding 4 fractions. 1H NMR analysis of these indicated the presence of

• before mentioned conditions to yield 4 subfractions: 3.1–3.4. Fraction 3.2 (44 mg) was analysed with the NMR system. Complex spectra obtained from VLC fraction 3.2 by NMR analysis indicated the presence of a wide range of secondary metabolites. This VLC fraction was thus subsequently subjected to further

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• methylation was intended to be examined. For UV–vis spectroscopy 50 µM solutions in 5% DMSO (v/v) in enzyme assay buffer were used, as this reflects the enzyme assay conditions. However, for LC-HRMS and NMR analysis, a higher concentration of 10 mM in methanol was necessary to receive reliable chromatograms

• mixtures (Figure 3). Proton NMR analysis implied photostationary states comprising a relative percentage of 45% (Z)-2b and 57% (Z)-2f, respectively after 100 minutes of 254 nm irradiation. The NMR spectra can be found in Supporting Information File 1. The degree of photoisomerization could not be enhanced

Multiple threading of a triple-calix[6]arene host

• Veronica Iuliano,
• Roberta Ciao,
• Emanuele Vignola,
• Carmen Talotta,
• Patrizia Iannece,
• Margherita De Rosa,
• Annunziata Soriente,
• Carmine Gaeta and
• Placido Neri

Beilstein J. Org. Chem. 2019, 15, 2092–2104, doi:10.3762/bjoc.15.207

• + [n × (1.5 × 10−3 mmol), n = 1–6] were dissolved in 0.5 mL of CDCl3. Then, the solution was sonicated for 5 min and transferred in a NMR tube for 1D and 2D NMR spectra acquisition. Determination of Kapp values by quantitative 1H NMR analysis. The samples were prepared by dissolving 6 (1.5 × 10−3 mmol

Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids

• Jürgen Krauß,
• Monika Klimt,
• Markus Luber,
• Peter Mayer and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2085–2091, doi:10.3762/bjoc.15.206

• submitted to extremely strong acidic conditions by refluxing with concentrated (37%) aqueous hydrochloric acid (entry 6), a new product 6 was formed in almost quantitative yield. The 1H NMR analysis clearly indicated that the entire carboxanilide partial structure got lost under these conditions. However