Allostreptopyrroles A–E, β-alkylpyrrole derivatives from an actinomycete Allostreptomyces sp. RD068384

• Marwa Elsbaey,
• Naoya Oku,
• Mohamed S. A. Abdel-Mottaleb and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2024, 20, 1981–1987, doi:10.3762/bjoc.20.174

• structures were elucidated by 1D and 2D NMR spectroscopic analyses, HRESIMS, and chemical derivatization. The absolute configurations of compounds 2 and 3 were predicted by comparison of experimental and calculated specific rotation data. Compounds 1–5 are the first examples of natural pyrroles substituted

• . Analysis of 1H NMR, 13C NMR (Table 1), and HSQC spectra revealed a formyl group (δC 186.3/δH 9.89), an olefinic methine (δC 131.1/δH 7.64), an acyl carbonyl carbon (δC 163.3), three non-protonated olefinic carbons (δC 133.4, 126.4, and 123.1), a deshielded non-protonated sp3 carbon (δC 70.1), six sp3

• HRESITOFMS and NMR analytical data (Table 2), inferring that compounds 2 and 3 were isomers of 1. In fact, their NMR spectra were closely similar to those for 1 except a little difference in the alkyl side chain terminus. In a COSY spectrum of 2, the terminal doublet methyl proton was correlated with an

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

• , experimental procedures, and characterization data. Supporting Information File 30: Copies of NMR spectra. Funding This work was partially supported by a Grant-in-Aid for Scientific Research on Innovative Areas “Hybrid Catalysis for Enabling Molecular Synthesis on Demand” (JP17H06447) and a Grant-in-Aid for

Radical reactivity of antiaromatic Ni(II) norcorroles with azo radical initiators

• Siham Asyiqin Shafie,
• Ryo Nozawa,
• Hideaki Takano and
• Hiroshi Shinokubo

Beilstein J. Org. Chem. 2024, 20, 1967–1972, doi:10.3762/bjoc.20.172

• analysis, which revealed that two alkyl substituents were located on the same side of the molecule (Figure 2a). Compared to the planar structure of 1 (Figure 2b) [2], 2a displays a nonplanar structure due to the sp3 carbon atoms adjacent to the nitrogen atoms. The 1H NMR spectrum of 2a confirmed that the

• . Supporting Information Supporting Information File 26: Experimental procedures, compound characterization data including NMR and MS spectra, additional crystal data and details from DFT calculations. Funding This work was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI grants

1,2-Difluoroethylene (HFO-1132): synthesis and chemistry

• Liubov V. Sokolenko,
• Taras M. Sokolenko and
• Yurii L. Yagupolskii

Beilstein J. Org. Chem. 2024, 20, 1955–1966, doi:10.3762/bjoc.20.171

• ], respectively, while reference [68] provides UV-spectral data of both isomers. 1H, 19F, and 13C NMR data [69][70] are given in Table 2. Chemistry of HFO-1132 Isomerization Iodine-catalyzed cis–trans isomerization of 1,2-difluoroethylene and corresponding equilibrium measurements were described in the 1960s [47

• ]. Additionally, when the reaction was performed using DMSO-d6 (or CD3CN) and CH3ONa, H/D exchange occurred already at ambient temperature (25 °C, 20 h) [78]. The formation of CDF=CDF was confirmed by NMR spectroscopy, namely by the change of signal multiplicity in the 19F NMR spectra of E- and Z-isomers of 1,2

• -difluoroethylene and the disappearance of vinyl protons resonances in the 1H NMR spectra [78]. Addition to the C=C bond Halogen addition: 1,2-Difluoroethylene was reported to react with chlorine [46][79] and bromine [51] under irradiation, yielding 1,2-difluoro-1,2-dihaloethanes in moderate to high yield (Scheme 9

Regioselective alkylation of a versatile indazole: Electrophile scope and mechanistic insights from density functional theory calculations

• Pengcheng Lu,
• Luis Juarez,
• Paul A. Wiget,
• Weihe Zhang,
• Krishnan Raman and
• Pravin L. Kotian

Beilstein J. Org. Chem. 2024, 20, 1940–1954, doi:10.3762/bjoc.20.170

• Scheme 1 compound 6 was treated with isopropyl iodide (7) in DMF in the presence of sodium hydride to provide products 8 and 9 in 38% and 46% yields, respectively. The structures of both compounds were unambiguously assigned using X-ray crystallography and 1H and nuclear Overhauser effect (NOE) NMR

• moisture-sensitive reagents were performed under a nitrogen or argon atmosphere. Silica gel chromatography was performed using prepacked silica gel columns (RediSep® Rf, Teledyne ISCO). An aluminum block atop a hotplate with a thermocouple was used to heat reactions to the specified temperatures. NMR

• purified by chromatography (silica [24 g], eluting with EtOAc in hexane from 0–70%) to give methyl 5-bromo-1-alkyl-1H-indazole-3-carboxylate, in 90–98%. For 15a, 284.5 mg, 90%, as a white solid. Mp 141.3 °C; 1H NMR (300 MHz, DMSO-d6) δ 8.19 (dd, J = 1.9, 0.7 Hz, 1H), 7.82 (dd, J = 9.0, 0.7 Hz, 1H), 7.65

A new platform for the synthesis of diketopyrrolopyrrole derivatives via nucleophilic aromatic substitution reactions

• Vitor A. S. Almodovar and
• Augusto C. Tomé

Beilstein J. Org. Chem. 2024, 20, 1933–1939, doi:10.3762/bjoc.20.169

• than the oxygen due to the preferential existence of 4-hydroxypyridine in the pyridin-4-one tautomeric form [37][38][39]. The structures of dyes 3a–f, 4a, 4d and 4f were unambiguously established through their 1H, 13C and 19F NMR and mass spectra. The 1H NMR spectra of the symmetrical compounds

• the protons of the N–CH2C6F5 and N–CH2C6F4XR groups, respectively. All 19F NMR spectra confirmed the selective substitution of the 4-fluorine atoms (in one or in two rings) by the disappearance of the signal corresponding to the resonance of those atoms. Mass spectra of compounds 3a–f, 4a, 4d and 4f

• apparatus. NMR spectra were recorded on a Bruker DRX 300 Avance operating at 300.13 MHz (for 1H NMR), at 75.47 MHz (for 13C NMR) and 282 MHz (for 19F NMR). Deuterated chloroform (CDCl3) was used as the solvent and tetramethylsilane (TMS) as the internal reference. The chemical shifts (δ) are expressed in

Negishi-coupling-enabled synthesis of α-heteroaryl-α-amino acid building blocks for DNA-encoded chemical library applications

• Matteo Gasparetto,
• Balázs Fődi and
• Gellért Sipos

Beilstein J. Org. Chem. 2024, 20, 1922–1932, doi:10.3762/bjoc.20.168

• each reaction (Supporting Information File 1). Supporting Information Supporting Information File 14: Experimental part and NMR spectra. Acknowledgements The authors thank Dr. Attila Sveiczer and Dr. Mounir Raji for the consultations and technical support during the practical work of the project, and

Novel oxidative routes to N-arylpyridoindazolium salts

• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2024, 20, 1906–1913, doi:10.3762/bjoc.20.166

• -arylpyridoindazolium salts S1–S3 was confirmed with HRMS and 1H, 13C and 19F NMR data; the complete assignment of the signals was performed using 2D NMR methods. The N–N bond formation was additionally confirmed via comparison of the 1H spectra for the salts and their diarylamine precursors. The absence of the signals

• corresponding diaryl amines A1–A3 (). Supporting Information Supporting Information File 8: Analytical data, NMR and MS spectra. Funding This work was supported by Russian Science Foundation (Project number 22-73-00040). The NMR part of this work was supported by M. V. Lomonosov Moscow State University

Electrochemical radical cation aza-Wacker cyclizations

• Sota Adachi and
• Yohei Okada

Beilstein J. Org. Chem. 2024, 20, 1900–1905, doi:10.3762/bjoc.20.165

• with stirring. The solution was diluted with water and extracted with dichloromethane. The combined organic layers were dried over Na2SO4, filtered, and concentrated in vacuo. Yields were determined by 1H NMR analysis using benzaldehyde as an internal standard (Table 1). Silica gel column

• cyclization.a Supporting Information Supporting Information File 6: General remarks and characterization data, including copies of 1H and 13C NMR spectra. Funding This work was supported in part by JSPS KAKENHI Grant No. 22K05450 (to Y. O.), and TEPCO Memorial Foundation (to Y. O.).

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

• information, X-ray crystallographic data, synthetic procedures, analytical data and NMR spectra for the reported compounds. Acknowledgements We thank the Research Center for Magnetic Resonance, the Center for Chemical Analysis and Materials Research, and the Center for X-ray Diffraction Methods of Saint

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

• a [1,5]-H shift [19], indazolo[3’,2’:2,3]imidazo[1,5-c]quinazolin-6(5H)-one 18 (Scheme 7) [20]. The favorable host–guest interaction between 14 and the reactants (demonstrated by 2D NMR and FTIR spectroscopy as well as by scanning electron micrography), combined with the acidity of the succinyl

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• ’ with a methoxy group in position C(6) in the 1H NMR spectrum when using m-anisidine (3c) only with benzaldehyde (4b, for detailed information, see Supporting Information File 1). It should be mentioned that three-component condensation leading to the formation of 5-aryldeazaflavins 1 usually proceeds

• -aryldeazaalloxazines in any case. Finally, the unsubstituted derivative 2x was formed with a yield of only 15% using DMF/AlCl3. The isolated products 2a–x were characterized by 1H, 13C NMR and mass-spectral methods. The 1H NMR spectra of 5-aryldeazaalloxazines 2a–x, along with protons of aryl substituents of aldehyde

• moiety and pyrimido[4,5-b]quinoline core, contained singlets with 3H intensity of the N(1)–CH3 and N(3)–CH3 groups of the barbituric acid fragment at 3.20–3.56 ppm. The 13C NMR spectra of 5-aryldeazaalloxazines 2a–x were represented by groups of singlets at 27.9–57.2 and 100.0–160.5 ppm. The

Chiral bifunctional sulfide-catalyzed enantioselective bromolactonizations of α- and β-substituted 5-hexenoic acids

• Sao Sumida,
• Ken Okuno,
• Taiki Mori,
• Yasuaki Furuya and
• Seiji Shirakawa

Beilstein J. Org. Chem. 2024, 20, 1794–1799, doi:10.3762/bjoc.20.158

• and solvents. Substrate scope. Larger-scale synthesis and transformations of bromolactonization product 3a. Supporting Information Supporting Information File 20: Experimental procedures, characterization data, copies of NMR spectra, and copies of HPLC charts. Funding K.O. thanks the JSPS for a

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

• tetrafluoroborate, BF4−) to form difluoroiodane 6. The formation of difluoroiodane 6 was identified by a singlet at −23.0 ppm in the 19F NMR spectrum. As expected, the aromatic signals in the 1H NMR spectrum shifted downfield from a doublet at 7.21 ppm and a triplet at 7.56 ppm for iodine(III) substrate 10 to 7.71

• ppm and 7.96 ppm, respectively, for iodine(V) product 6. Similarly, the 13C NMR spectrum showed a major downfield shift for the aromatic carbon attached to iodine from a chemical shift of 105.3 ppm in iodine(III) substrate 10 to 132.4 ppm for difluoroiodane(V) product 6. Since Selectfluor was shown to

• studies of hypervalent iodine(V) fluorides in solution The stability of hypervalent iodine(V) fluorides 6, 20, 21 and 22 was studied in dry acetonitrile-d3 by 1H and 19F NMR spectroscopy over 7 days under an argon atmosphere. All four hypervalent iodine(V) fluorides were stable for the 7-day period. When

Ugi bisamides based on pyrrolyl-β-chlorovinylaldehyde and their unusual transformations

• Alexander V. Tsygankov,
• Vladyslav O. Vereshchak,
• Tetiana O. Savluk,
• Serhiy M. Desenko,
• Valeriia V. Ananieva,
• Oleksandr V. Buravov,
• Yana I. Sakhno,
• Svitlana V. Shishkina and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2024, 20, 1773–1784, doi:10.3762/bjoc.20.156

• stirring for three hours (Scheme 3, conditions A). However, the results of this attempted post-Ugi transformation were quite unexpected: Instead of acid 11, we isolated the amide of the unsaturated derivative of pyruvic acid 10a according to the 1H and 13C NMR spectra and mass spectrometry data. In order

• conventional thermal heating, amide 10a was isolated, albeit in a lower yield and accompanied with tar formation. In addition to the 1H, 13C NMR spectra and mass spectrometry data, the structure of compound 10d was established by X-ray diffraction analysis (Figure 3). It was also found that the substituents at

• case of bisamides 5d, 6a, 6c, 7b, 8a, and 8c (Table 2), additional transformation products were also isolated from the reaction mixture. According to 1H and 13C NMR, MS, and X-ray diffraction studies these were the corresponding ketobisamides 12, which are products of a nucleophilic substitution of the

Synthesis and characterization of 1,2,3,4-naphthalene and anthracene diimides

• Adam D. Bass,
• Daniela Castellanos,
• Xavier A. Calicdan and
• Dennis D. Cao

Beilstein J. Org. Chem. 2024, 20, 1767–1772, doi:10.3762/bjoc.20.155

• sodium hydroxide, followed by acidification with HCl, yielded a mixture of carboxylic acids and anhydrides 5, as evidenced by 1H NMR spectroscopy (Figure S13 in Supporting Information File 1). Gratifyingly, purification of these mixtures was not necessary as they could be used directly for imidization

Harnessing unprotected deactivated amines and arylglyoxals in the Ugi reaction for the synthesis of fused complex nitrogen heterocycles

• Javier Gómez-Ayuso,
• Pablo Pertejo,
• Tomás Hermosilla,
• Israel Carreira-Barral,
• Roberto Quesada and
• María García-Valverde

Beilstein J. Org. Chem. 2024, 20, 1758–1766, doi:10.3762/bjoc.20.154

• explained by the intramolecular hydrogen bond formed between the hydroxy group and the carbamide substituent, which explains the high deshielding observed in the 1H NMR spectra for the signal of the OH group (around 8.5 ppm). As before, we also explored the stereochemical outcome in the synthesis of

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

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

• of each isomer, as illustrated by Equation 1. The value for c at the PSS can be found using other spectroscopic methods, such as NMR spectroscopy [17] or the TEM (for Thulstrup, Eggers, and Michl) method [34][35]. With a known value for c, the spectrum of the second component can be found by a simple

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

• : 3.61 Å [31]). Beginning with the electron-deficient and thereby highly reactive NHIs 1a and 1c, we explored the potential for a ligand-exchange process on the iodane via 1H NMR spectroscopy by combining equimolar quantities of NHI and n-octanol (2). When the tetrazole-substituted hydroxy(aryl)iodane 1a

• was added, no significant shifts in the NMR spectral signals were detected, probably due to the poor solubility of the iodane. Conversely, with the addition of the red tetrazine salt 1c, a significant downfield shift was observed for the alpha-carbon protons from 3.51 ppm to 4.55 ppm, as illustrated

• with common iodine(III) reagents by 1H NMR spectroscopy (Figure 4). After 60 h the measurements revealed a higher yield of aldehyde 4a using 1a (68%) compared to 1c (30%) under the influence of AlCl3. As a comparison, the use of PIDA (5b) and IBA (5c) with the additive resulted in a significantly lower

Ring opening of photogenerated azetidinols as a strategy for the synthesis of aminodioxolanes

• Henning Maag,
• Daniel J. Lemcke and
• Johannes M. Wahl

Beilstein J. Org. Chem. 2024, 20, 1671–1676, doi:10.3762/bjoc.20.148

• chosen as a preferred solvent because it is known to facilitate Norrish–Yang-cyclizations and allows simple analysis by nuclear magnetic resonance (NMR) spectroscopy [10]. Our results are summarized in Table 1. When p-toluenesulfonyl (Ts) was used as a PG at nitrogen, azetidine 3a was obtained in 81

• added to 3a (Scheme 3a). Formation of hemiketal 8 was expected to occur, which would facilitate ring opening by a 5-exo-tet cyclization. While we did observe the formation of hemiketal 8 by NMR spectroscopy, we were unable to detect any ring-opened products 9, even when adding Lewis acids or Brønsted

• acids. Comparison of the effect of structural variations on the photoreaction. Supporting Information Supporting Information File 2: Experimental procedures, characterization data and copies of NMR spectra. Acknowledgements Generous support from the Johannes Gutenberg-Universität Mainz is acknowledged

Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• and NMR analysis of the natural product, no knockout studies were performed to identify which enzyme is responsible for the S-methylation. The authors propose LopH as the most likely enzyme, as it shares modest sequence and structural similarity with other MTs. This also hints at a possible new MT

Polymer degrading marine Microbulbifer bacteria: an un(der)utilized source of chemical and biocatalytic novelty

• Weimao Zhong and
• Vinayak Agarwal

Beilstein J. Org. Chem. 2024, 20, 1635–1651, doi:10.3762/bjoc.20.146

• known parabens (2, 5, 6, and 11), five new ones (7–10, and 12) were identified. Their structures were elucidated by high-resolution mass spectrometry (HRMS) and 1D and 2D nuclear magnetic resonance (NMR). The configuration in 8 and 10 remained undetermined. Antimicrobial activities of compounds 2 and 5

• from this bacterium by comparison of their 1H NMR and MS data with those reported in literature (Figure 7). Alkaloids Three new alkanoyl imidazoles 21–23 (Figure 8) were isolated from a culture extract of a Microbulbifer bacterium isolated from a scleractinian coral [15]. Their structures were

• determined using a combination of NMR spectroscopy and chemical derivatization experiments, adding new members to this class of imidazole-containing natural products such as the nocarimidazoles A and B reported from a marine-derived actinomycete Nocardiopsis sp. before [126]. Compound 21 was determined to be

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

• for 35Cl and 37Cl isotopes, respectively, with an approximately 3/4 and 1/4 proportion. The symmetry of the obtained compound TP1 gives simple NMR spectra, with the 31P NMR spectrum showing a singlet signal (Figure 2) and the signal at 169.5 ppm, on the 13C NMR spectrum, confirming the presence of a

• proposed disubstitution pattern, with MS showing MH+ and MH+ + 2 isotope peaks due to the presence of chlorine in the molecule. In the 1H NMR spectrum, the CH2P protons appear as a doublet signal at 3.14 ppm, due to the coupling with the 31P atom of the phosphonate group (Figure 2). The chemical shift of

• different conditions tested. The spectroscopic data are in agreement with the proposed structure for compound TP3 (Scheme 5), namely the presence of the chlorine atom in the mass spectrum, due to the presence of isotope peaks, the signal at 168.2 ppm at 13C NMR spectrum attributed to the carbon atom bonded

Generation of multimillion chemical space based on the parallel Groebke–Blackburn–Bienaymé reaction

• Evgen V. Govor,
• Vasyl Naumchyk,
• Ihor Nestorak,
• Dmytro S. Radchenko,
• Dmytro Dudenko,
• Yurii S. Moroz,
• Olexiy D. Kachkovsky and
• Oleksandr O. Grygorenko

Beilstein J. Org. Chem. 2024, 20, 1604–1613, doi:10.3762/bjoc.20.143

• synthesis of compound library 4, experimental section including compound characterization data, and copies of NMR spectra. Supporting Information File 13: Structures of reactants 1, 2, and 3. Supporting Information File 14: Parallel synthesis of compound library 4. Supporting Information File 15

• : Experimental part. Supporting Information File 16: Copies of NMR spectra. Acknowledgements Dedicated to the memory of Kyrylo Burmagin and Yaroslav Mayboroda, students of Chemical Faculty at Taras Shevchenko National University of Kyiv, trainees at Enamine, and volunteer soldiers who died defending their