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

• actinometry, thus demonstrating the reliability of our setup. Keywords: isomerization; molecular photoswitches; photochemistry; photon flux; UV–vis spectroscopy; Introduction Photoswitches are molecules that can undergo a light-driven structural rearrangement to populate a metastable state of the initial

• 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

• molecular switch by UV–vis absorption spectroscopy in operando. We provide all the information necessary to build the setup as well as the scripts and examples to retrieve the quantum yields of forward and backward isomerization of a molecular photoswitch following the evolution of the absorption in the low

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

• 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

• , respectively) in CD3CN (500 µL) was monitored via 1H NMR spectroscopy. Substrate scope of aldehydes and ketones synthesized from the corresponding alcohols. Isolated yields. Reaction conditions: 1a (700 µmol), alcohol (500 µmol), and method A HCl (37%, 500 µmol) in EtOAc (2.5 mL) or method B TBACl (500 µmol

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

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

• 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

• conduction properties of new membranes were evaluated by electrochemical impedance spectroscopy (EIS) at 60 °C at different relative humidity (RH) conditions. The results showed higher proton conductivities than recast Nafion membrane and similar or better proton conductivities than commercial Nafion N115

• , for example, to the performance of fuel cells. The study of the protonic conductivities of the new modified membranes were determined, in-plane, at 60 ºC, in different relative humidity (RH) conditions (40, 60 and 80%), through electrochemical impedance spectroscopy (EIS) (Figure 5). A prepared recast

• characterization of the dopants was carried out by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). 1H, 13C and 31P NMR characterization was done using different one- and two-dimensional techniques, and were obtained on a Bruker Avance III HD

Supramolecular assemblies of amphiphilic donor–acceptor Stenhouse adducts as macroscopic soft scaffolds

• Ka-Lung Hung,
• Leong-Hung Cheung,
• Yikun Ren,
• Ming-Hin Chau,
• Yan-Yi Lam,
• Takashi Kajitani and
• Franco King-Chi Leung

Beilstein J. Org. Chem. 2024, 20, 1590–1603, doi:10.3762/bjoc.20.142

• moiety. The excellent photoswitchability in organic medium and the photoresponsiveness in aqueous medium, driven by visible light, were investigated by UV–vis absorption spectroscopy. The assembled supramolecular nanostructures were confirmed by electron microscopy, while the supramolecular packing was

• , Figures S13–S33. Photochemical properties of DAn in organic medium The photochemical properties of DAn were first studied in organic solvent by UV–vis absorption spectroscopy. The synthesized DA11 in THF solution (20 µM) showed a strong absorption band at 470–685 nm in the UV–vis absorption spectrum

• reversibility of the other compounds, DAn with shorter alkyl linkers were also examined in THF solvent by UV–vis absorption spectroscopy, where they showed photochemical properties similar to those of DA11 (Figure 1a and Figure 1b). THF solutions of DA7 and DA6 showed a strong absorption band at 470–685 nm

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

• Yu Fan,
• Ahmed El Rhaz,
• Stéphane Maisonneuve,
• Emilie Gillon,
• Maha Fatthalla,
• Franck Le Bideau,
• Guillaume Laurent,
• Samir Messaoudi,
• Anne Imberty and
• Juan Xie

Beilstein J. Org. Chem. 2024, 20, 1486–1496, doi:10.3762/bjoc.20.132

• decreases concomitantly to the appearance of two new bands at 312 and 438 nm (Figure 2, blue line). Two isosbestic points can also be observed at 310 and 429 nm. The back Z→E photoisomerization can be achieved by illumination at 485 nm (Figure 2, red line). 1H NMR spectroscopy has been used to determine the

• . Depending on the corresponding galactosyl azobenzenes, the Z-isomer is pure from 87 to 99%. Spectroscopy measurements were performed on ligand solution just before each experiment to check the efficiency of the isomerization, with results as indicated in Table 2. In all experiments, strong exothermic peaks

Synthesis of 1,2,3-triazoles containing an allomaltol moiety from substituted pyrano[2,3-d]isoxazolones via base-promoted Boulton–Katritzky rearrangement

• Constantine V. Milyutin,
• Andrey N. Komogortsev and
• Boris V. Lichitsky

Beilstein J. Org. Chem. 2024, 20, 1334–1340, doi:10.3762/bjoc.20.117

• be noted that based on NMR spectroscopy data the synthesized product 3b exists as a mixture of E/Z isomers. Having in hands hydrazone 3 we tried to perform the Boulton–Katritzky rearrangement into corresponding 1,2,3-triazole 4. In order to achieve the best yields of product 4b we varied the used

• spectroscopy and high-resolution mass spectrometry. Moreover, X-ray analysis was used for confirmation of structure of compound 4g (Figure 1). A plausible mechanism of the studied rearrangement is presented in Scheme 5. At first, anion A is generated from starting hydrazone 3 under action of base. Next

• obtained the recyclized product 6a (Scheme 6), whose structure was confirmed by 1H, 13C NMR spectroscopy, high-resolution mass spectrometry and X-ray analysis. Based on the aforementioned reaction we have synthesized a set of pyrazolylisoxazoles 6 (Scheme 7). The proposed mechanism of investigated

Computation-guided scaffold exploration of 2E,6E-1,10-trans/cis-eunicellanes

• Zining Li,
• Sana Jindani,
• Volga Kojasoy,
• Teresa Ortega,
• Erin M. Marshall,
• Khalil A. Abboud,
• Sandra Loesgen,
• Dean J. Tantillo and
• Jeffrey D. Rudolf

Beilstein J. Org. Chem. 2024, 20, 1320–1326, doi:10.3762/bjoc.20.115

• crystallographic information. Acknowledgements We acknowledge the University of Florida Center for Nuclear Magnetic Resonance Spectroscopy and Ion Ghiviriga for excellent NMR support. We acknowledge the University of Florida Mass Spectrometry Research and Education Center (MSREC), which is supported by the NIH

Sustainable tandem acylation/Diels–Alder reaction toward versatile tricyclic epoxyisoindole-7-carboxylic acids in renewable green solvents

• Ayhan Yıldırım

Beilstein J. Org. Chem. 2024, 20, 1308–1319, doi:10.3762/bjoc.20.114

• in a much shorter time (Table 1, entry 4) when the temperature of the reaction medium was increased to 50 °C. According to X-ray and Raman spectroscopy techniques, triglyceride molecules in liquid form are arranged in a dynamic chain-like conformation [114][115][116]. As the temperature of the

Diameter-selective extraction of single-walled carbon nanotubes by interlocking with Cu-tethered square nanobrackets

• Guoqing Cheng and
• Naoki Komatsu

Beilstein J. Org. Chem. 2024, 20, 1298–1307, doi:10.3762/bjoc.20.113

• -TOF mass spectra. Upon extraction of SWNTs with the nanobracket and copper(II), in situ-formed square Cu-nanobrackets are found to interlock SWNTs to disperse them in 2-propanol. The interlocking is confirmed by Raman spectroscopy after thorough washing of the extracted SWNTs. Pristine SWNTs were

• (Scheme 2) [11]. The products were fully characterized by 1H and 13C NMR, and MALDI-TOF mass spectroscopy (see Supporting Information File 1). The total yield of 4b (5.5%) based on 2,7-dibromopyrene is much lower than that of 4a (44%) [11], because a larger amount of the product 4b was lost in the

• moieties absorbing ≈465 nm light (Figure 1b) should be excited at the resonance Raman spectroscopy using a 488 nm laser. This is supported by the observation that the excitation at 633 and 785 nm where 1b did not show any absorption (Figure 1b) did not give any Raman signals [20]. Extraction of SWNTs with

Synthesis of indano[60]fullerene thioketone and its application in organic solar cells

• Yong-Chang Zhai,
• Shimon Oiwa,
• Shinobu Aoyagi,
• Shohei Ohno,
• Tsubasa Mikie,
• Jun-Zhuo Wang,
• Hirofumi Amada,
• Koki Yamanaka,
• Kazuhira Miwa,
• Naoyuki Imai,
• Takeshi Igarashi,
• Itaru Osaka and
• Yutaka Matsuo

Beilstein J. Org. Chem. 2024, 20, 1270–1277, doi:10.3762/bjoc.20.109

• -functionalized compound (t-Bu-FIDS) was chosen for further studies in this work. To identify the formation of the thiocarbonyl group, Fourier transform infrared spectroscopy (FTIR) was conducted as shown in Figure 1a. The carbonyl stretching vibration peak of t-Bu-FIDO at 1720 cm−1 disappeared, indicating all

• around 1000 cm−1 for t-Bu-FIDS. Ultraviolet–visible (UV–vis) spectroscopy of t-Bu-FIDS in o-DCB exhibited two prominent UV absorption bands with peaks at 257 nm and 320 nm (Figure 1b). The absorption at 257 nm indicated the integrity of the fullerene cage chromophore. The absorption peak at 320 nm was

Synthesis and optical properties of bis- and tris-alkynyl-2-trifluoromethylquinolines

• Stefan Jopp,
• Franziska Spruner von Mertz,
• Peter Ehlers,
• Alexander Villinger and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1246–1255, doi:10.3762/bjoc.20.107

• steady state absorption and fluorescence spectroscopy which give insights of the influence of the substitution pattern and of the type of substituents on the optical properties. Keywords: alkynes; catalysis; fluorescence; heterocycles; palladium; Introduction Quinoline is a well-known core structure

• investigated via steady-state absorption and fluorescence spectroscopy and gives first insights into the structure–optical property relationship of polyalkynylated quinolines. In particular, high fluorescence quantum yields have been determined for all studied compounds. Variation of the substitution pattern

Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• increased when the triplet efficiently reacts in a catalytic cycle such that turnover numbers exceeding 4400 are achievable with this organocatalyst. Keywords: energy transfer; laser spectroscopy; organocatalyst; photoredox; time-resolved spectroscopy; Introduction The emergence of photoredox chemistry in

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• with arylamines follows a complex reaction pathway, leading to a mixture of compounds. We established the possible reaction pathways using 77Se NMR spectroscopy and single-crystal X-ray crystallographic studies. Density functional theory (DFT) calculations were carried out to understand the relative

• benzenoid→quinonoid excitonic transitions, respectively, which was characteristic of polyaniline existing as emeraldine free base [41][42]. The polyaniline nature was further confirmed by FTIR spectroscopy (Figure S2, Supporting Information File 1). The broad peak observed in the range of 3300–3400 cm−1 was

• based on HRMS data. To test whether the isolated black solid was a single compound or an isomeric mixture of compounds 1 and 2, 77Se NMR spectroscopy could be a convenient tool. Unfortunately, 77Se NMR data was not reported in the work of Bhat et al. [37]. With this question in mind, the reaction was

Introduction of peripheral nitrogen atoms to cyclo-meta-phenylenes

• Koki Ikemoto and
• Hiroyuki Isobe

Beilstein J. Org. Chem. 2024, 20, 1207–1212, doi:10.3762/bjoc.20.103

• achieved with one-pot Suzuki–Miyaura coupling to arrange phenylene rings and pyridinylene rings in an alternating fashion. Analyses with UV–vis spectroscopy showed changes in the photophysical properties with nitrogen doping, and X-ray crystallographic analyses experimentally revealed the presence of

• biased charges on the peripheral nitrogen atoms. Keywords: cross coupling; macrocycles; nitrogen doping; UV–vis spectroscopy; X-ray charge density analysis; Introduction Graphitic carbonaceous sheets of graphene continue to attract considerable attention, which lead us to explore structural defects

• nitrogen-doped [n]CMPs (3) containing outward-radiating nitrogen dopants. The properties and structures were investigated with UV–vis spectroscopy and X-ray crystallography, which revealed the fundamental properties of the nitrogen dopants in the macrocyclic structures. Results and Discussion Nitrogen

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• then undergo condensation with formaldehyde providing an N-phenylmethanimine intermediate which was confirmed by 1H NMR spectroscopy. In the final step, the imine undergoes hydrogenation with Mn3-b to yield the N-methylated product (Scheme 16). In 2020, Maji et al. synthesized manganese(I) complexes

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps

• Qian Liu and
• Glen P. Miller

Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97

• conditions by utilizing a 7000-fold excess of dimethyl acetylenedicarboxylate (DMAD) at room temperature. The reactions were monitored by UV–vis spectroscopy. Compound 2 undergoes rapid reaction with DMAD under these conditions and is more than 90% consumed after 2.5 hours (Figure 8, top). Conversely

• spectroscopy. After 51 hours of reaction in boiling CH2Cl2, Diels–Alder adduct 27 was observed in 22% yield. Compound 27 was identified by 1H NMR and 13C NMR spectroscopies as well as high-resolution ESI mass spectrometry. Although the lack of reactivity observed for 3 and 23 limited our kinetic analysis, we

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

• Tural N. Akhmedov,
• Ajeet Kumar,
• Daken J. Starkenburg,
• Kyle J. Chesney,
• Khalil A. Abboud,
• Novruz G. Akhmedov,
• Jiangeng Xue and
• Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

• -bonding dicyanopyrazinoquinoxaline (DCPQ) suspensions with excess potassium hydroxide, resulting in moderate to good yields. Both families of compounds were analyzed by UV–vis and NMR spectroscopy, where the consequences of hydrogen bonding capability could be assessed through the structure–property

• secured due to the favorable hydrogen bonding (O–H∙∙∙N) between the oxime units; this idea is supported by 1H NMR spectroscopy which shows the presence of two distinct hydroxyl proton signals. The reduction of 7d in the presence of Pd/C and hydrazine monohydrate afforded 1,10-phenanthroline-5,6-diamine

• and its high thermal stability. Optical properties The electronic properties of the DCPQs 1a–6a and DPQDs 1b–7b were explored by UV–vis absorption spectroscopy in dimethyl sulfoxide (DMSO) at 25 °C (Figure 3). The electronic absorption spectra of DCPQs exhibited structureless bands with λmax values

Spin and charge interactions between nanographene host and ferrocene

• Akira Suzuki,
• Yuya Miyake,
• Ryoga Shibata and
• Kazuyuki Takai

Beilstein J. Org. Chem. 2024, 20, 1011–1019, doi:10.3762/bjoc.20.89

• diamagnetic molecule (S = 0, no spin magnetism) compared with other metallocenes [17]. However, FeCp2 is easily oxidized to a monovalent cation, the electronic structure of which is magnetic (S = 1/2). Electron spin resonance (ESR) spectroscopy revealed the spin magnetism of cationic FeCp2 accommodated in

• (SQUID) [21][22] and X-ray magnetic circular dichroism (XMCD) spectroscopy [23]. However, only a tiny paramagnetic behavior of encapsulated ferrocene was observed, and no magnetic host–guest interactions were reported due to the diamagnetic nature of CNTs. Activated carbon fibers (ACFs) consist of a

• photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, magnetic susceptibility, and electron-spin resonance (ESR). Experimental Commercially available ACFs (Kuraray, FR-20), of which the precursor was a phenol-resin, were pre-heat-treated in a glass tube at 200 °C

A Diels–Alder probe for discovery of natural products containing furan moieties

• Alyssa S. Eggly,
• Namuunzul Otgontseren,
• Carson B. Roberts,
• Amir Y. Alwali,
• Haylie E. Hennigan and
• Elizabeth I. Parkinson

Beilstein J. Org. Chem. 2024, 20, 1001–1010, doi:10.3762/bjoc.20.88

• used, the reaction proceeded well with 78% conversion when monitored by both MS and NMR spectroscopy. However, when sodium chloride was used instead of sodium hydroxide, no conversion was observed. Temperature was also taken into consideration; temperatures above 55 °C were not considered because we

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• determined by 1H NMR spectroscopy (Scheme 15). More recently, in 2016, still in Söderberg’s group, the synthesis of 2,2′-bi-1H-indoles, 2,3′-bi-1H-indoles, 3,3′-bi-1H-indoles, indolo[3,2-b]indoles, and indolo[2,3-b]indoles via reductive cyclization Pd-catalyzed was developed [36]. The reaction was possible

Synthesis and properties of 6-alkynyl-5-aryluracils

• Ruben Manuel Figueira de Abreu,
• Till Brockmann,
• Alexander Villinger,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 898–911, doi:10.3762/bjoc.20.80

• of different functional groups was tested. The influence of different functional groups on the physical properties was studied by ultraviolet–visible (UV–vis) and fluorescence spectroscopy, providing new insights into the potential applications of uracil-based structures. Keywords: catalysis; cross

• . Applications and tolerance to a wide range of functional groups have been tested. Furthermore, their physical properties were analyzed by ultraviolet–visible and fluorescence spectroscopy. Results and Discussion Synthesis The synthetic strategy for the desired compounds is based on a four-step sequence

• synthesized by other methods and the single Suzuki reaction on uracil is well studied [42][69][70][71]. Physical properties The photophysical properties of selected derivatives were investigated by steady-state absorption and photoluminescence spectroscopy. The influence of the substitution pattern on the

Confirmation of the stereochemistry of spiroviolene

• Yao Kong,
• Yuanning Liu,
• Kaibiao Wang,
• Tao Wang,
• Chen Wang,
• Ben Ai,
• Hongli Jia,
• Guohui Pan,
• Min Yin and
• Zhengren Xu

Beilstein J. Org. Chem. 2024, 20, 852–858, doi:10.3762/bjoc.20.77

• to cyclopentane skeleton, as well as its stereochemistry, was originally elucidated as 1' as shown in Figure 1, on the basis of detailed analysis of 1D and 2D NMR spectroscopy. Spiroviolene was also found to be produced by several bacterial strains harboring SvS homologs [6][7], as well as putative

Ortho-ester-substituted diaryliodonium salts enabled regioselective arylocyclization of naphthols toward 3,4-benzocoumarins

• Ke Jiang,
• Cheng Pan,
• Limin Wang,
• Hao-Yang Wang and
• Jianwei Han

Beilstein J. Org. Chem. 2024, 20, 841–851, doi:10.3762/bjoc.20.76

• reaction was performed in the presence of 10 mol % Cu(OTf)2 and 1.0 equivalent of K2CO3 in DCE at a temperature of 80 °C. To our delight, the reaction afforded 3,4-benzocoumarin 3aa in a 27% yield (Table 1, entry 1). The structure of 3aa was confirmed through NMR spectroscopy and mass spectra analysis

• isolated as stable solids, whose structures were fully characterized by NMR spectroscopy. As shown in Table 3, we utilized 2-naphthol and 1-naphthol as template substrates to react with various unsymmetrical 2-ester-substituted diaryliodonium salts. Remarkably, iodonium salts 2 proved to be versatile in