Synthesis of tetrahydrofuro[3,2-c]pyridines via Pictet–Spengler reaction

• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2023, 19, 991–997, doi:10.3762/bjoc.19.74

• with an insufficient stabilization of the generated iminium cation due to the presence of a strong electron-withdrawing nitro group (for 3n), and due to the fact that the electron deficiency of the pyridine ring is strongly manifested in an acidic media (for 3m). In addition, the disadvantages of the

• developed method include the impossibility of using aliphatic aldehydes (for example, 2-phenylacetaldehyde (2o)), that is also explained by an insufficient stabilization of the resulting cation and the impossibility of cyclization. We also did not detect the formation of the target product when 1H-pyrrole-2

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• ) complex and to close the cycle), thus furnishing compound 6 comprised of an eight-membered ring. The related stabilization effect of the conjugated product 6 might be the thermodynamic driving force for this radical coupling. An alternative route (not showen) would be that, the α-amidoalkyl radical

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• molecules to double stranded DNA or RNA polynucleotides usually affect the double helix stability. This stabilization or destabilization was revealed as a change of the polynucleotide’s melting temperature (ΔTm value) which was the difference of the Tm value of free polynucleotide and the Tm value of

• polynucleotide secondary structure. Concurrently, no monomer fluorescence signal at 400 nm changed, except a small increase upon poly dGdC–poly dGdC addition. Negligible thermal stabilization (Table S1, Figures S6–S8, Supporting Information File 1) did not support the classical intercalation of phenanthridine

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

• Manuel Pedrón,
• Jana Sendra,
• Irene Ginés,
• Tomás Tejero,
• Jose L. Vicario and
• Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

• cyclohexanes clearly showed that NCIs increase with the size of the tether (Figure 5) and the same effect is expected to account for the reagents. In general, a barrier could increase either by a destabilization of the transition structure or the stabilization of the reagents. In our case, the more stable is

Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis

• Nicoleta G. Hădărugă,
• Gabriela Popescu,
• Dina Gligor (Pane),
• Cristina L. Mitroi,
• Sorin M. Stanciu and
• Daniel Ioan Hădărugă

Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30

• provide the on-site protection of hazelnut oil components against oxidative degradation, in combination with a protection/stabilization through CD nanoencapsulation. Moreover, the apparent water solubility, bioaccessibility, bioavailability, and controlled release of the guest bioactive compounds can also

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• ligand to the iron center in alkyl–alkenyl cross-coupling reactions featuring Grignard reagents, but was involved in the formation of the bulky dication [Mg(NMP)6]2+, the presence of the latter contributing to the kinetic stabilization of the on-cycle active species [Me3FeII]− (Table 2, entry 1) [35

• thiolate leaving groups, and stabilize at a molecular level active FeII species. In both cases, a beneficial effect should be observed at a molecular level on the stabilization and/or the reactivity of on-cycle species, given that phosphate electrophiles proved to afford satisfying coupling yields in the

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• the π-type orbitals on the unsaturated carbons on the eliminated alkenylsulfide chain fragment, leading to resonance stabilization. This effect is absent in lithiated 2. For the fully saturated lithiated 1,4-dithiane derived from 1, the higher intrinsic reactivity of the tetragonal alkyllithium

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• analysis of lactam 19l. In order to shed light on the details of the reaction mechanism, we have performed carefully designed mechanistic studies which consist of experiments on the effect of β-silicon stabilization, the alkene geometry of the α,β-unsaturated acyl chloride reactants, and adventitious water

• ) group via the β-silicon stabilization effect [36][37][38] as supported by computational studies [35]. The desilylation of intermediate 9 with the chloride of another molecule of 8 would result in the formation of final aza-Nazarov product 7 along with TMSCl (Scheme 1d). Five-membered nitrogen

• differences between acyl chlorides 23 and 6 in the examined aza-Nazarov cyclizations can be understood when the electron densities on the two olefin moieties are considered. Indeed, while both of the proposed intermediates 29 and 9 (Scheme 1) can benefit from the β-silicon stabilization effect, the olefinic

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• of the desired trisubstituted alkene due to stabilization of the incipient radical at C9. Furthermore, HAT reduction served to only deliver the thermodynamic product of the trans-decalin. Similarly, the C9–C11 alkene can serve as an ideal handle to C11-hydroxylated products, such as 42, through a

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• following example of styrene diamination by a chiral aryl iodide, the higher efficiency of the proposed catalyst compared to simpler aryl iodides was attributed to the additional stabilization of the I(III) intermediate by chelation via n–σ* interactions and hydrogen bonding [147] (Scheme 33). The

Supramolecular approaches to mediate chemical reactivity

• Pablo Ballester,
• Qi-Qiang Wang and
• Carmine Gaeta

Beilstein J. Org. Chem. 2022, 18, 1463–1465, doi:10.3762/bjoc.18.152

• reactants are confined in the restricted space provided by an enzyme binding pocket, the increase in local concentration, due to the proximity effect, the stabilization of intermediates and transition states cause the acceleration of the reaction. Thus, learning from natural enzymes, novel supramolecular

• constrictions, stabilization of species, and solvent exclusion phenomena occurring in the molecular containers isolated spaces [6]. Consequently, the classical rules of organic reactivity are often violated [6][11]. Taking into account the above considerations, we organized this thematic issue focused on

• distributions when performed inside the containers compared to the bulk solution. As mentioned above, activation of substrates, stabilization of intermediates and transition states through intermolecular interactions was established as one of the fundamental factors of supramolecular catalysis, and among these

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• and NI-PTZ-O is presented. In addition, the impact of solvent on the energy of the states is included. When moving from apolar to polar solvents a little increase in the energy gap between 1CT and 3LE is observed (amounting to up to 0.13 eV in acetonitrile), which is mostly due to the stabilization of

1,4,6,10-Tetraazaadamantanes (TAADs) with N-amino groups: synthesis and formation of boron chelates and host–guest complexes

• Artem N. Semakin,
• Ivan S. Golovanov,
• Yulia V. Nelyubina and
• Alexey Yu. Sukhorukov

Beilstein J. Org. Chem. 2022, 18, 1424–1434, doi:10.3762/bjoc.18.148

• stabilization of the complex through weak hydrophobic interactions of with tert-butyl groups of Boc. We believe that by adjustment of the substituents on the amide/carbamate groups, receptors for supramolecular sensing of alcohols [44] could be designed based on 3N-TAADs of type 4. Further research in this

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

• flavor control; it could be used to improve the stabilization, quality, efficiency and persistence of repellents, disinfectants, perfumes, laundry detergents and flavoring agents [15][16]. Another strategy to prolong the longevity of the fragrance and, as an additional benefit, to increase the stability

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• stabilization of reactive conformations by chelation or dipole control. Keywords: aldol addition; ketoesters; natural products; total synthesis; Introduction Vicinal ketoesters contain a carbonyl group adjacent to an ester group. One keto group results in α-ketoesters 1 and two vicinal keto groups lead to α,β

• bearing an electrophilic keto group as reactive site. The vicinal arrangement of carbonyl groups allows the stabilization of reactive conformations by chelation or dipole control. Suitable key reactions are e.g., aldol additions, carbonyl ene reactions, Mannich reactions, and additions of organometallic

Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• units (Figure 3). Consequently, the fact reveals that compared to the (D–π)2Ph-type structure, the (D–π)2-type structure can cause not only the stabilization of the LUMO energy level but also the delocalization of the HOMO and LUMO over the whole molecule, leading to a narrower HOMO–LUMO band gap of OTT

• properties both in solution and the solid state, but also can cause delocalization of the HOMO and the LUMO over the whole molecule as well as the stabilization of the LUMO energy level, leading to a narrower HOMO–LUMO band gap of OTT-2 than OTK-2, that is, the bathochromic shift of photoabsorption band from

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• backbone stabilization through intra-residue hydrogen bonds but also to intermolecular associations. The high capacity of N-(methylamino)peptoids to establish intermolecular hydrogen bonds was notably deduced from pronounced concentration-dependent N–H chemical shift variation in 1H NMR and the

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• , thermodynamic stabilization quantitatively drives the reaction to the hetero-assembly 59, simply by mixing the components in the correct stoichiometric ratio (Figure 13). Various nanorotor assemblies are possible by this approach. The dynamics of the four-component rotor 59 = [Cu2(55)(57)(60)]2+ cannot be

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• –A(–D) structures, while an additional donor unit led to a slight red shift in photoluminescence by the stabilization of the charge-transfer singlet excited states (1CT). Most importantly, the additional donor unit not only lowers the 1CT energy but also is bringing the T1 energy to the approximation

A resorcin[4]arene hexameric capsule as a supramolecular catalyst in elimination and isomerization reactions

• Tommaso Lorenzetto,
• Fabrizio Fabris and
• Alessandro Scarso

Beilstein J. Org. Chem. 2022, 18, 337–349, doi:10.3762/bjoc.18.38

• the active site of the enzyme. Once bound, substrate activation is carried out by specific amino acid side chains that adorn the inner surface of the cavity by means of a combination of covalent and/or weak intermolecular interactions leading to the stabilization of intermediate species and transition

• all these reactions is the combination of its weak Brønsted acidity [42] that, by protonation of the substrate, leads to the formation of cationic species [43] and the stabilization of the latter through cation–π interactions [44] within the electron-rich aromatic cavity of the capsule, thus providing

• excess of tetrabutylammonium bromide (3) as a competitive guest for the capsule, to demonstrate the importance of the presence of an accessible cavity, and iii) acetic acid (4) in order to mimic only the Brønsted acidity of the capsule without providing the stabilization properties related to the

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• p–π conjugation. This stabilization is not possible with alkyl groups, explaining why 2-alkylaziridines did not generate the corresponding products. Intermediates C undergo an intramolecular nucleophilic attack to yield ethyl (oxazolidin-2-ylidene)alkanoates D, which further isomerize to more stable

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• = Ph, R1 = 4-NO2) were analyzed, a significant difference was observed compared to the other compounds in the series 3. Thus, we can say that these characteristics exist because there is more stabilization of the excited state in a polar environment (DMSO and MeOH), adding to a possible push–pull

• ) and 3bc (R = Ph, R1 = 5-OMe) (Table 1). These values observed according to the solvent may be related to the stabilization of the excited state in each solution. Regarding the Stokes shifts (SS), higher values were observed for derivatives in a more polar solvent (DMSO and MeOH) than in CHCl3 (Table 1

• ) and also depending on the electronic properties of the substituents in the molecules. According to the characteristics and properties described herein, once again, we can attribute these differences to the stabilization of the excited states in more polar solvents combined with the properties of

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones – an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

• Alla I. Vaskevych,
• Nataliia O. Savinchuk,
• Ruslan I. Vaskevych,
• Eduard B. Rusanov,
• Oleksandr O. Grygorenko and
• Mykhailo V. Vovk

Beilstein J. Org. Chem. 2021, 17, 2787–2794, doi:10.3762/bjoc.17.189

• nitrogen atom to nitrenium intermediates occurred initially; further stabilization of these species resulted in the formation of hydroxylated lactams [44][45][46][47][48], azaspirocycles [49][50][51][52][53], or tricyclic nitrogen-containing heterocycles [44][53]. Our study commenced with the synthesis of

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• ) would allow for the stabilization of the radical by the methoxy substituent in the ortho position to the departing substituent. The methoxy substituent then presumably loses a hydrogen radical to form acetic acid and intermediate 17c. Further loss of formaldehyde would restore aromaticity and furnish