Extension of the π-system of monoaryl-substituted norbornadienes with acetylene bridges: influence on the photochemical conversion and storage of light energy

• Robin Schulte,
• Dustin Schade,
• Thomas Paululat,
• Till J. B. Zähringer,
• Christoph Kerzig and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 3061–3068, doi:10.3762/bjoc.20.254

• )2 and the corresponding arylnorbornadienes without an acetylene bridge, such as 1o, leading to efficient and quantitative conversion to the quadricylanes (Scheme 4) [38]. Hence, we assumed that triplet-sensitized isomerization of the mono-, bis-, and tris-norbornadiene derivatives with an

• by 1H NMR spectroscopy. Initially, all derivatives showed the isomerization reactions to the corresponding quadricyclane derivatives, as identified by the characteristic 1H NMR signal pattern of the quadricyclane fragment with five multiplets at around 1.6 ppm, 1.7 ppm, 1.8 ppm, 2.1 ppm, and 2.2 ppm

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• (Figure 5A) [56]. In the structure, α-CD was located on the trans-azobenzene moiety before ultraviolet (UV) irradiation, after which it moved to the methylene moiety based on the cis-isomerization of the azobenzene by UV irradiation. After the azobenzene moiety was moved back to the trans-isomer via

• α-CD-based rotaxane comprising a stilbene axle that was synthesized by the Suzuki coupling reaction to light irradiation (Figure 6, right) [58]. In this structure, α-CD was first located on the trans-stilbene moiety, after which it moved to the benzene ring moiety via the cis-isomerization of the

• stilbene framework by 335 nm light irradiation before returning to the stilbene moiety via trans-isomerization induced by the 280 nm light irradiation; this system is also reversible. The change in the local position of CD is significantly reflected in the ICD behavior of this system. Kodaka and co-workers

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

• in case of the oxoindirubins 41 seems to decrease this unfavorable dipol situation in case of the E-configured isomers. It is likely, that an E/Z isomerization takes place under acidic conditions. The barrier of this equilibrium is most likely lowered by the presence of the ring oxygen as it

Copper-catalyzed yne-allylic substitutions: concept and recent developments

• Shuang Yang and
• Xinqiang Fang

Beilstein J. Org. Chem. 2024, 20, 2739–2775, doi:10.3762/bjoc.20.232

• formal [4 + 1] and [4 + 2] cyclizations were carried out through substitution by an alkynyl copper-driven dearomatization/rearomatization/cyclization/isomerization process (Scheme 40). Li, Yu and Liu et al. [78] achieved the asymmetric catalyzed dearomative [4 + 1] spiroannulation of nonfunctionalized 1

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

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

• lack of geometrical isomerization of the C–N double bond of the dithiolation products [32]. The thioselenation product 6’, an imine derivative, can be converted to a β-lactam derivative by [2 + 2] cycloaddition with ketene generated in situ. For example, thioselenation of RNC (R = (EtO)2P(O)–CH2) gave

Understanding X-ray-induced isomerisation in photoswitchable surfactant assemblies

• Beatrice E. Jones,
• Camille Blayo,
• Jake L. Greenfield,
• Matthew J. Fuchter,
• Nathan Cowieson and
• Rachel C. Evans

Beilstein J. Org. Chem. 2024, 20, 2005–2015, doi:10.3762/bjoc.20.176

• molecules to create photosurfactants (PS), whose molecular shape and polarity can be modified using light [4][5][6]. Of the PS studied, most use an azobenzene (Azo) photoswitch that undergoes trans-to-cis (E-to-Z) isomerization on irradiation with UV light, typically forming a photostationary state (PSS

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• perchlorate as electrolyte. It is interesting to notice that the isomerization of the product and subsequent ring closure discussed above (see Scheme 17) did not occur under these conditions (Scheme 24) [73]. In 2023, Hajra et al. provided an electrochemical method for the C(sp2)–H sulfonylation of aromatic

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

• ]. Along with this, photoisomerization is described in patent literature [71][72][73][74]. It was shown that the experimentally observed enthalpy of isomerization (0.928 kcal/mol [47]) is in agreement with the calculated difference in the total energy of the two isomers (0.959 kcal/mol [65][75]). Cis-1,2

• required 2–3 weeks at the same temperature. In this case, sufficient E–Z isomerization of the starting olefin occurred during the reaction, and the major product was 5,6-endo,endo-difluoro-1,2,3,4,7,7-hexachlorobicyclo[2.2.1]-2-heptene, which was formed from (Z)-1,2-difluoroethylene (Scheme 20). Both

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 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

• setup for isomerization quantum yield determination is reported. The setup combines fiber-coupled LEDs, a commercially calibrated thermopile detector for measurement of the photon flux, and a fiber-coupled UV–vis spectrometer. By solving the rate equations numerically, isomerization quantum yields can

• 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

• reactant. This isomerization can be reversed by light of a different wavelength or thermal stimuli. Depending on the nature of the reactant, different classes of photoreactions can be utilized: double bond isomerizations, electrocyclization, cycloadditions, and electron-, hydrogen-, or group transfer [1

Divergent role of PIDA and PIFA in the AlX₃ (X = Cl, Br) halogenation of 2-naphthol: a mechanistic study

• Kevin A. Juárez-Ornelas,
• Manuel Solís-Hernández,
• Pedro Navarro-Santos,
• J. Oscar C. Jiménez-Halla and
• César R. Solorio-Alvarado

Beilstein J. Org. Chem. 2024, 20, 1580–1589, doi:10.3762/bjoc.20.141

• -4–Br. The next step is a deprotonation assisted by the released Br3Al–OAc species. This allows the formation of the AcO–AlBr2 salt via TS3–Br and the trans intermediate I-5–Br, which contains a Br–I(Ph)–O–naphthyl bond of 2.14 Å length. The last step is the bromination of I-5–Br by isomerization to

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

• . 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

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• intramolecular Cannizzaro reaction was demonstrated by the group of Schmalz in the total synthesis of the marine antibiotic pestalone [86]. They observed a facile isomerization of the pestalone derivatives 55/57 into the intramolecular lactone derivatives rac-56a,b which features a Cannizzaro–Tishchenko-type

Domino reactions of chromones with activated carbonyl compounds

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1256–1269, doi:10.3762/bjoc.20.108

• dienes has to proceed with full conversion and in high yield as the they cannot be purified by chromatography. Distillation is also problematic, as dienes containing substituents located at carbon atom C-2 readily undergo isomerization reactions. The reactions of 1,3-bis(silyloxy)-1,3-butadienes with

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

• with a quantum yield of 0.34. The pronounced triplet formation was exploited for the isomerization reaction of (E)-stilbene to the Z-isomer and the cyclization of cinnamyl chloride. Catalyst degradation mainly occurs through the long-lived Aza-H triplet (28 µs), but the photostability is greatly

• underlying reaction mechanism. On the other hand, the relatively high triplet formation quantum yield of Aza-H along with its triplet energy on the order of 2.3 eV permit efficient and metal-free reactions via energy transfer catalysis, as shown for the photosensitized isomerization of stilbene and cinnamyl

• from Ref [77], transient absorption spectrum of Aza-H with 0.3 mM MV2+ and the difference spectrum of both spectra (cyan). E) Emission lifetime of Aza-H in the presence (dark yellow) and absence (black) of 0.3 mM MV2+. Stilbene isomerization and additional energy transfer experiments. A) and B) Triplet

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

• dehydrogenated secondary alcohols into ketone B and diol into aldehyde A. Further, aldol condensation occurred between the ketone and aldehyde and produced α,β-unsaturated ketone C, which was subsequently hydrogenated by complex Mn1-c, followed by allyl isomerization, which led to the formation of hydroxy ketone

Novel route to enhance the thermo-optical performance of bicyclic diene photoswitches for solar thermal batteries

• Akanksha Ashok Sangolkar,
• Rama Krishna Kadiyam and
• Ravinder Pawar

Beilstein J. Org. Chem. 2024, 20, 1053–1068, doi:10.3762/bjoc.20.93

• transformation into a high energy photoisomer [8][9][10][11][12][13]. This photoisomer then can be stored for a certain period and thermal energy can be released when triggered with heat, light, catalyst, etc. The back isomerization of the metastable photoproduct regenerates the parent molecule for continuing

• [10]. These properties include the large storage energy, high gravimetric energy storage density, large barrier for thermal back isomerization reaction, photoabsorption in the visible range, high quantum yield of photoisomerization, and so forth [10]. Photoswitches like dihydroazulene

• photoswitching cycle. The activation energy required to trigger the transformation of the metastable photoisomer to the parent diene is called the thermal back isomerization barrier. The TBR barrier governs the duration of storage of harvested solar energy in the MOST devices. Photoswitching systems exhibiting a

Entry to new spiroheterocycles via tandem Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazoarylidene succinimides

• Alexander Yanovich,
• Anastasia Vepreva,
• Ksenia Malkova,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 561–569, doi:10.3762/bjoc.20.48

• 1H NMR spectroscopy data, one of its components was the product of the migration of the double bond of the benzylidene fragment into the succinimide cycle – compound 22. Finally, a compound with a longer side chain 24, obtained from 2-(2-bromoethoxy)ethanol (23), underwent exclusively isomerization

• -membered cycle in the latter case. The main direction of the reaction in these examples becomes isomerization (migration of a proton when it is captured by an intermediate anion) or other side processes. In the conjugated anion formed as a result of deprotonation (Scheme 8), one would also expect

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• a terminal phenanthroline receptor substituent was synthesized. Upon irradiation in acetonitrile or DMSO with light of 436 nm, they underwent Z–E isomerization of the C=C bond, followed by very fast N→O migration of the acyl group and the formation of nonemissive O-acylated isomers. These isomers

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

(E,Z)-1,1,1,4,4,4-Hexafluorobut-2-enes: hydrofluoroolefins halogenation/dehydrohalogenation cascade to reach new fluorinated allene

• Nataliia V. Kirij,
• Andrey A. Filatov,
• Yurii L. Yagupolskii,
• Sheng Peng and
• Lee Sprague

Beilstein J. Org. Chem. 2024, 20, 452–459, doi:10.3762/bjoc.20.40

• -1,1,1,4,4,4-hexafluorobut-2-enes have been investigated. A simple, one-pot procedure for the preparation of a new allene (1,1,4,4,4-pentafluorobuta-1,2-diene) and some of its transformations is presented. Keywords: allenes; dehydrohalogenation; halogenation; 1,1,1,4,4,4-hexafluorobut-2-enes; isomerization

• method it was possible to achieve complete dehydrobromination of (Z)-isomer 3b and isolation of (E)-isomer 3a in pure form in 35% yield (Scheme 2). Unexpectedly the (E)-isomer 3a, upon long-term storage, transforms into the (Z)-isomer 3b. Therefore, we studied the isomerization of olefin 3a in the

• iodine monochloride were also studied. Synthesis of 2,3-dibromo-1,1,1,4,4,4-hexafluorobutane (2). Synthesis of (E)-butene 3a. Isomerization reaction of (E)-butene 3a to (Z)-butene 3b. Synthesis of 2-chloro-3-iodo-1,1,1,4,4,4-hexafluorobutane (5). Dehydrohalogenation reaction of 2-chloro-3-iodo

Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges

• Eiichi Kayahara,
• Yoshiyuki Mizuhata and
• Shigeru Yamago

Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38

• ). The other two isomers, 2 and 3 (Figure 5b,c), with two CPPs tilted at 15.6° and 45.5°, are 2.5 and 4.2 kJ mol−1 less stable than complex 1, respectively. The stability among the isomers is low, and the activation energy for isomerization should be very low. Therefore, all isomers are expected to be

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• , this class of compounds is prone to valence isomerization via 6π-electrocyclization leading to the formation of heteroatom-containing norcaradiene, and oxepine has been shown to exist in equilibrium with its valence isomer benzene oxide [37]. In contrast with the parent oxepine, which is isolable at

• design of pentacene’s soluble precursor, as reported by Müllen and Herwig [14], is depicted in the top left. Valence isomerization of chalcogen heteropines and subsequent cheletropic extrusion in the case of sulfur, selenium and tellurium derivatives. Early example of phenanthrene synthesis via a

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• of prospective applications of indigo photoswitches. Keywords: indigoid dyes; photochemistry; photophysics; photoswitching; E–Z isomerization; Review Historical milestones in the development of photochromic indigo derivatives 1954: first reported photochromic indigo derivative – N,N'-diacetylindigo

• –E isomerization of N,N'-substituted indigos Since 1980s: detailed mechanistic and structural studies of the photoisomerization of indigo 2015: first report on photochromism of N,N'-diBOC indigos (follow-up studies in 2019, 2021) 2017: rationalisation of the design of indigo photochromes: symmetrical

• irradiation with orange light in several solvents [40]. However, due to the technical limitations of the spectrometer, Pummerer and Marondel were not able to detect the short-living Z-11a in aromatic solvents such as benzene, bromobenzene and pyridine. Nevertheless, the E–Z isomerization of 11a was observed