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

• was prepared and the photoisomerization behavior of these compounds was studied. Surprisingly, all N,N'-diarylindigos were obtained as mixtures of E/Z isomers. The computational study showed the negligible energy differences between the Z- and E-isomers of 19a–h in the ground state, which explained

Cyclization of 1-aryl-4,4,4-trichlorobut-2-en-1-ones into 3-trichloromethylindan-1-ones in triflic acid

• Vladislav A. Sokolov,
• Andrei A. Golushko,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2023, 19, 1460–1470, doi:10.3762/bjoc.19.105

• reflux in toluene [19] (Scheme 4). By this route, mainly E-isomers of compounds 2 were formed except for compounds 2c,i,m which were obtained as mixtures of E,Z-isomers (see Experimental section). However, under the reaction conditions in the presence of TsOH, the hydroxy ketones 1k,p–s bearing strong

Cyclodextrin-based Schiff base pro-fragrances: Synthesis and release studies

• Attila Palágyi,
• Jindřich Jindřich,
• Juraj Dian and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2022, 18, 1346–1354, doi:10.3762/bjoc.18.140

• was next studied by 1H NMR and SH-GC for selected imino-β-CD. The prepared imines could also be mixtures of E/Z isomers, but no attempts were made to isolate them for the reason metioned above. Also, the prepared imines proved to be difficult to purify by chromatographic methods due to their low

AlBr₃-Promoted stereoselective anti-hydroarylation of the acetylene bond in 3-arylpropynenitriles by electron-rich arenes: synthesis of 3,3-diarylpropenenitriles

• Yelizaveta Gorbunova,
• Dmitry S. Ryabukhin and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2663–2667, doi:10.3762/bjoc.17.180

• rather regioselectively giving mainly Z-isomers of nitriles 2, as products of an anti-addition of hydrogen and the aryl group to the carbon–carbon triple bond. Only in three cases, mixtures of E,Z-isomers (2b,l,n) in a ratio of ≈1:1 were obtained. The E,Z-configuration of compounds 2a–o was determined by

Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

• Andrey I. Puzanov,
• Dmitry S. Ryabukhin,
• Anna S. Zalivatskaya,
• Dmitriy N. Zakusilo,
• Darya S. Mikson,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2417–2424, doi:10.3762/bjoc.17.158

• nucleophilic arene molecules, species B should afford substances 5 as products of hydroarylation of the acetylene bond of the starting compounds 3. Indeed, reaction of 5-acetylenyl-1,2,4-oxadiazoles 3a–c with excess of TfOH at room temperature for 1 h resulted in the quantitative preparation of E/Z-isomers of

• o-, m-, p-xylenes) in TfOH at room temperature for 1 h leading to products of hydroarylation of the acetylene bond, compounds (E/Z)-5a–g, were carried out (Scheme 5). This reaction gave E/Z-isomers 5b–g, their stereochemical configuration was determined by H,H NOESY correlations between the vinyl

• proton and aromatic protons (see Supporting Information File 1). In the case of the reaction with o-xylene, pairs of E/Z-isomers of two regioisomers, (E/Z)-5b and (E/Z)-5b1, were obtained. We also checked the reaction of oxadiazole 3a with benzene under the action of Lewis acids AlCl3, AlBr3 and acidic

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• mixture of E/Z isomers. Further, double bond cleavage of nucleoside 120 followed by benzoylation produced the benzoic acid ester of the hemiacetal analogue 121 which was finally converted into double-headed nucleoside 122 via Vorbrüggen coupling reaction followed by deprotection using methanolic ammonia

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• experiments, we found that the desired cyclization took place smoothly to give rise to heterotricycle (rac)-16 in 64% yield (over two steps) as a 4:1 mixture of the E/Z isomers at the acetoxyalkene moiety, when the reaction was conducted with 0.05 equiv of catalyst 14 at 69 °C. The highly efficient overall

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

• Clément Q. Fontenelle,
• Thibault Thierry,
• Romain Laporte,
• Emmanuel Pfund and
• Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

• heterocyclic ether 10, the addition of TBAB as a bromide source was explored. To our delight, after 30 min at 0 °C, the crude 19F NMR showed that only 4% of 10 and 96% of 9 as an 84:16 E/Z mixture had formed (Table 3, entry 2). Separation of the two E/Z isomers proved challenging by column chromatography and a

Synthesis and highly efficient light-induced rearrangements of diphenylmethylene(2-benzo[b]thienyl)fulgides and fulgimides

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Valerii V. Tkachev,
• Andrey N. Utenyshev,
• Olga Yu. Karlutova,
• Alexander D. Dubonosov,
• Vladimir A. Bren,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2020, 16, 1820–1829, doi:10.3762/bjoc.16.149

• -, Z-isomers and closed forms C were identified with the use of 1H and 13C NMR spectroscopy and their molecular structures confirmed by X-ray diffraction studies. Experimental General: The 1H and 13C NMR spectra in CDCl3 were obtained on an integrated analytical LC-SPE-NMR-MS AVANCE-600 system from

• electrocyclic reaction followed by the thermally induced 1,5-hydrogen shift reaction. This transformation represents a highly efficient process in comparison with the similar low-efficiency rearrangements of known diphenylmethylene(aryl(hetaryl))fulgides. The key structures of these light-induced reactions – E

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• same group studied the direct trifluoromethylselenolation of α-brominated unsaturated carbonyl compounds with [(bpy)CuSeCF3]2 and CsF as the base (Scheme 5, top) [21]. The products were obtained with good yields as a mixture of E/Z isomers. The authors postulated the formation of a copper(III) complex

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• –Z photoisomerization is achieved by irradiating in the region of the high-energy π–π* band for the E-isomer, whereas Z–E photoisomerization occurs through irradiation in the low-energy n–π* band of the Z-isomer. However, an overlap in the absorbances between E/Z isomers causes incomplete

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

• ; toluene, reflux, 3 h, 76%; d) NH3, MeOH, 40 °C, 3 d, 87–95%. Photocyclization and oxidation reaction of 2b upon UV irradiation. Reagents and conditions: a) 4-fluoroaniline, oxone, HAc, 60 °C, 14 d, 42%; b) NH3, MeOH, rt, 3 d, 98%. Sirt1–3 inhibition for compounds 2a–h, 4a/4b and 8a. Percentage of E/Z

• -isomers of 11 at the thermal equilibrium (∆), and photostationary states (PSS) after 365 nm and 452 nm irradiation. Sirt1-3 inhibition for compound 11 at the thermal equilibrium (∆) and the photostationary state (PSS) after 5 minutes of 365 nm irradiation. Supporting Information The Supporting

Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• 1d always provided a 4:1 mixture of the E/Z isomers of 11, while cis-1d gave the expected Z-isomer of 11 exclusively (Table 3, entries 3 and 4). The two isomers could, however, be separated by chromatography. Interestingly, the cis or trans-epoxydiynes 1e stereospecifically and solely provided the

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3⁺ + 2]-cycloaddition/rearrangement reactions

• Lin-bo Luan,
• Zi-jie Song,
• Zhi-ming Li and
• Quan-rui Wang

Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155

• (0.85 mmol), AcOH (1 mL). bIsolated yield. cRatio of E/Z isomers was not determined. Synthesis of tricyclic benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepinium salts 10. Reaction conditions: substrate 8 (0.25 mmol) in CH2Cl2 (2 mL), nitrile 9 (0.35 mmol), AlCl3 (0.35 mmol), CH2Cl2 (5 mL), −40 °C for 0.5 h

Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ⁶-sulfanyl)acetic acid esters with aldehydes

• Anna-Lena Dreier,
• Andrej V. Matsnev,
• Joseph S. Thrasher and
• Günter Haufe

Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25

• electron-donating substituents in p-position. Consequently, the formation of a mixture of E/Z-isomers would be expected. Therefore, we were in favor of an alternative mechanism involving elimination subsequent to the addition step. According to Denmark’s mechanism [5] for the silicon Mukaiyama aldol

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• corresponding adduct 44 in 93% yield. Importantly, both stereoisomers obtained were oxime E,Z-isomers with the C-7 relative configuration being the same as in myrioneurinol. Subsequent deoxygenation and reduction of aldoxime followed by transformation of the malonate unit to the formyl group furnished

A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes

• Grzegorz Mlostoń,
• Paulina Pipiak,
• Róża Hamera-Fałdyga and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 1900–1906, doi:10.3762/bjoc.13.185

• ; found: C, 39.68; H, 2.25. 1,2-Diphenyl-1,2-bis(selenophen-2-yl)ethene (9f, mixture of E/Z isomers, ratio 2:1.2). Yield: 156 mg (71%); chromatographic purification (petroleum ether/CHCl3 8:2). Yellow crystals; mp 221–223 °C; IR (KBr) ν: 3044 (w), 1483 (w), 1439 (m), 1233 (m), 1201 (w), 1071 (w), 1021 (w

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• EI mass spectra of 1 and 2. No significant differences were detectable between the E/Z-isomers of each compound. Nevertheless, contrary to open chain compounds, characteristic differences could be found for the positional isomers. While most ions are similar in both spectra, the prominent ion m/z 126

Thiazol-4-one derivatives from the reaction of monosubstituted thioureas with maleimides: structures and factors determining the selectivity and tautomeric equilibrium in solution

• Alena S. Pankova,
• Pavel R. Golubev,
• Alexander F. Khlebnikov,
• Alexander Yu. Ivanov and
• Mikhail A. Kuznetsov

Beilstein J. Org. Chem. 2016, 12, 2563–2569, doi:10.3762/bjoc.12.251

• interconverting E/Z-isomers at the exocyclic C=N bond (given in parentheses on Scheme 2) could be involved. Therefore we have thoroughly analyzed the spectroscopic data of thiazolidine 3a from 2D NMR experiments (NOESY, 13C,1H and 15N,1H-HSQC and HMBC) and made a full assignment of all signals. A large difference

• positions of the “jumping” hydrogen atom in the structure of 3b (see Supporting Information File 1). This confirms the two tautomeric A and I forms of thiazolidine 3b rather than E/Z-isomers with the endocyclic phenyl group. While in solution the ratio of tautomers is 1:1, in the solid state the A form

Construction of bis-, tris- and tetrahydrazones by addition of azoalkenes to amines and ammonia

• Artem N. Semakin,
• Aleksandr O. Kokuev,
• Yulia V. Nelyubina,
• Alexey Yu. Sukhorukov,
• Petr A. Zhmurov,
• Sema L. Ioffe and
• Vladimir A. Tartakovsky

Beilstein J. Org. Chem. 2016, 12, 2471–2477, doi:10.3762/bjoc.12.241

• studies of this remarkable cyclization are ongoing. Structure and isomerism in hydrazones 2–12 All newly obtained hydrazones were 2–12 characterized by 1H, 13C NMR spectroscopy and HRMS data. Most of the hydrazones were obtained as mixtures of E/Z-isomers (see Supporting Information File 1). The ratio of

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• crucial. In contrast to 1a and 1b, three coexisting isomeric species were observed with NMR spectroscopy in CDCl3 for tetrahydrobiisoindole “NU-BIPHEP(O)” 1c. This behaviour originates from an increased interconversion barrier between the E/Z isomers of the carbamate N–C(O) unit that is derived from a

Selective bromochlorination of a homoallylic alcohol for the total synthesis of (−)-anverene

• Frederick J. Seidl and
• Noah Z. Burns

Beilstein J. Org. Chem. 2016, 12, 1361–1365, doi:10.3762/bjoc.12.129

• reduced with dimethyl phosphonate [16][17]. While the mechanism of this Hirao reduction is not fully understood, the reaction was exquisitely mild and proceeded with high chemoselectivity for the geminal dihalide, delivering (−)-anverene (1) in high yield as a 7:1 mixture of E/Z isomers. Following

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• ]. Formation of the imine E-7 and Cr(CO)6 from the carbene complex Cr(CO)5(Z-6) requires heating to 170 °C for 3 days under CO pressure (Scheme 1c) [42]. At room temperature and in the presence of base (KOt-Bu), M(CO)5(Z-8) (M = Cr, W) simply isomerize to a mixture of E/Z isomers M(CO)5(E-8)/M(CO)5(Z-8