Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• subjected to the oxidative polymerization by using ferric chloride to obtain polymers 33–38 in 42–58% yields as shown in Scheme 8. These polymers possessed good thermal stability (Td > 400 °C) and most of them were soluble in organic solvents such as THF, chloroform, dichloromethane, xylene, and toluene

• -dibromo-6-(n-dodecyl)azulene (13) with 2,5-bis(trimethylstannyl)thiophene (44) under Stille reaction conditions produced the polymer 45 in 62% yield (Scheme 10). The Mn and PDI for polymer 45 were 5100 Da and 1.4, respectively and its thermal stability was excellent (Td = 404 °C). Polymer 45 exhibited

• , and 56 displayed good solubility in most of the commonly used organic solvents and GPC analysis revealed their number-average molecular weight (Mn) to be in the range of 25800 to 48600 Da with polydispersity in the range 1.29–1.9. They also exhibited excellent thermal stability as indicated by their

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• ][40][41]. The structures of some of the uridine derivatives are shown in Table 1. In general, the attachment of amine-functionalized groups on the pyrimidine C-5 position positively affects both the thermal stability and the nuclease resistance of the resulting amine-modified ONs. A tris-aminated

• significant improvement in Tm was observed when the functionalizing groups were changed from ethylenediamine to either trimethylenediamine (monomer 42) or putrescine (monomer 43), demonstrating that the length between the cationic amino group and the sugar scaffold is important for the thermal stability

• giving the best stabilization (up to 5.7 °C for four incorporations in an 18-mer ON relative to the control), whereas all gave similar and/or decreased thermal stability against RNA relative to the natural control ON [97]. It is noteworthy to mention that all monomers allowed the design of ASOs that were

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• ]. Interestingly and in contrast to other backbone-constrained PNAs, pyrrolidinyl α/β-dipeptide PNA formed PNA–DNA complexes having higher thermal stability compared to PNA–RNA complexes [63][64]. Most likely, the one atom longer PNA backbone, which is rigidified and preorganized by cyclic moieties, may align

• precursors in vitro [133]. Furan (F, Figure 8) as a reactive nucleobase mimic was well accommodated in a duplex with DNA without decreasing its thermal stability [134]. Upon oxidation of the furan ring, F-modified PNAs reacted preferentially with cytosine and adenine and irreversibly crosslinked with ssDNA

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• polymer with an effective ratio μh/μe = 3.94 cm2⋅V−1⋅s−1/3.50 cm2⋅V−1⋅s−1. Recently, diketopyrrolo[3,4-c]pyrrole (DPP) derivatives, which are highly conjugated electron-withdrawing heterocycles with high charge conductivity, broad absorption spectrum, photostability, and thermal stability have attracted

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

• group (Scheme 32) [71]. The double-headed nucleoside monomer 5′-O-(4,4′-dimethoxytrityl)-5-(thymin-1-yl)methyl-2′-deoxyuridine (130) was converted into the corresponding phosphoramidite at the C-3′-hydroxy group and then incorporated into oligonucleotides and was found to decrease the thermal stability

• phosphoramidites and then introduced into oligonucleotides. The thermal stability of DNA:DNA and DNA:RNA duplexes was determined and it was found that duplexes with a meta-substitution and a phenylacetylene linker were more stable than the corresponding para-substituted and phenyl-linker containing derivatives

• treatment with methanolic ammonia and DMA–DMF (Scheme 37) [71]. Both double-headed nucleoside monomers 143 and 146 were phosphoramidated at the C-3′ hydroxy group and incorporated into oligonucleotides. The synthesized oligonucleotides were found to decrease the thermal stability of the duplexes. However

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• interdisciplinary interest from both fundamental as well as applied viewpoint on account of their wonderful optoelectronic properties. The scientific interest in two-dimensional star-shaped PAHs particularly in truxene architectures arises because of their high thermal stability, exceptional solubility and ease

• ]. More interestingly, the high fluorescence quantum yield as well as the excellent photoluminescence quantum efficiency in addition to extraordinary thermal stability are the most significant characteristics of these systems. Interestingly, this versatile C3-symmetric aromatic framework can also formally

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• for water retention, but thermal stability of HGCM-vTA within the range of 150 °C to 318 °C has improved. Considering the water retention, the first trials of the hydrophobization process were designed to perform the hydrophobization with the swollen sample instead of using freeze-dried versions to

• the arbitrary photopolymerization process. In addition, we were not able to identify free polymer chains during the purification process, which indicates a covalent growth of polymers on a hydrogel host. It is expected that pore modification on networks will influence the thermal stability of the

• initial substrate. Regarding this, thermogravimetric analysis results confirmed the enhanced thermal stability for each employed polymer network compared to the initial substrate (Figure 6a). The HGCM curve is indicating the evaporation of entrapped water (up to 150 °C) followed by structural

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• given its low cost, recyclability, and high chemical/thermal stability [37][38][39]. Meanwhile, CN-K has a band gap of 2.72 eV with suitable valence band and conduction band potentials, which allows its promising use in organic synthesis for oxidation and reduction of various substrates [40][41][42][43

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• '-aminonucleoside couples to the 5'-H-phosphonate in the presence of a base (Scheme 1) [64]. In comparison with natural phosphodiester oligonucleotides, these modified oligonucleotides display improved nuclease resistance and an enhanced duplex thermal stability of 2.3–2.6 °C per linkage independent of nucleotide

• modification is accommodated in an A'-form duplex [75]. Interestingly, an unconventional C–H···O hydrogen bond was observed between the amide’s carbonyl oxygen and the nearby uracil C6–H6. The thermal stability of this modified duplex was, however, quite similar to native RNA. Typically, there is a decrease of

• 0.2–0.8 °C in the thermal stability of RNA/DNA hybrid duplexes for each AM1 modification [11][78]. NMR structural studies have shown that the AM1 modification is well tolerated in an RNA duplex, with little effect on the global structure [79]. Furthermore, siRNA duplexes with amide modifications at

DNA with zwitterionic and negatively charged phosphate modifications: Formation of DNA triplexes, duplexes and cell uptake studies

• Yongdong Su,
• Maitsetseg Bayarjargal,
• Tracy K. Hale and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2021, 17, 749–761, doi:10.3762/bjoc.17.65

• + modifications led to the formation of duplexes with a thermal stability that was less dependent on the ionic strength than native DNA duplexes. The thermodynamic analysis of the melting curves revealed that it is the reduction in unfavourable entropy, despite the decrease in favourable enthalpy, which is

• ) have an enhanced thermal stability in DNA triplexes and duplexes, a high binding affinity to RNA, and are nuclease resistant [22][26][27][28]. These properties have led to LNA (BNA) being used in various therapeutic ONs that have reached clinical trials [29]. However, the multistep synthesis of LNA and

• affinity with complementary RNA [35], and a destabilising effect on the thermal stability of G-quadruplexes [36] hinders its application. In contrast, a phosphate methylated linkage (POMe,) marginally destabilised complementary DNA but improved sequence specificity [37]. Recently, we synthesised a G-rich

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• catalysts in the form of ionic liquids (ILs) [209]. Advantages of metallated ILs include low flammability, high thermal stability and versatility. However, their “greenness” and toxicity are still debated [225][226]. Thus, amim[ZnCl3] (amin = 1-allyl-3-methylimidazolium, Table 4, entry 1) [227] and amim

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• extracellular matrix in higher animals. When introduced at a certain position in the structure, R-Flp and S-Flp exhibit prominent effects on the thermal stability of the protein. The effect originates from the stabilization of the pyrrolidine ring puckers, which has an effect on the packing of the triple helix

• S-Flp (Figure 6), which appears reproduced in the complex protein structure. A study of collagen mimetics demonstrated an elevated thermal stability for the collagen helix formed by repeating R-Flp-Gly-S-Mep units (where S-Mep is (4S)-methylproline) [118]. The collagen triple helix was found in the

Mesoionic tetrazolium-5-aminides: Synthesis, molecular and crystal structures, UV–vis spectra, and DFT calculations

• Vladislav A. Budevich,
• Sergei V. Voitekhovich,
• Alexander V. Zuraev,
• Vadim E. Matulis,
• Vitaly E. Matulis,
• Alexander S. Lyakhov,
• Ludmila S. Ivashkevich and
• Oleg A. Ivashkevich

Beilstein J. Org. Chem. 2021, 17, 385–395, doi:10.3762/bjoc.17.34

• : aminotetrazoles; DFT; mesoionic compounds; UV–vis spectra; X-ray analysis; Introduction 5-Aminotetrazoles are one of the most available and valuable tetrazole derivatives. So, due to the thermal stability and high nitrogen content the parent 5-aminotetrazole (1, Figure 1) is of practical interest as a gas

• thermal stability of the tetrazolium-5-aminides (see Supporting Information File 1 for more details). Some nucleophilic displacement reactions were carried out in order to show the higher reactivity of the aminides in comparison to the parent aminotetrazoles. The high nucleophilicity of the imine group in

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• molecules [38][39][40][41][42][43][44][45][46][47][48][49][50][51]. This is not surprising, taking into account the excellent thermal stability, the strong electron-donating nature, a good hole-transporting ability of the carbazole unit and, as a consequence, numerous applications of the carbazole-based

A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles

• Bingbing Lai,
• Meng Ye,
• Ping Liu,
• Minghao Li,
• Rongxian Bai and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2888–2902, doi:10.3762/bjoc.16.238

• higher temperature of 327–448 °C may be attributed to decomposition of the support skeleton [23]. The thermal stability of referential Resin-Cu catalyst was also investigated by TG analysis (Supporting Information File 1, Figure S3), showing a high thermal stability as well [24][25][26]. The above

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• substituents at the pyridine or imidazole part) to increase the Ni–ligand coordination strength. Strong coordination in turn improves the performance of the spin switch, namely the conversion rate to the cis isomer, the conversion rate to the high-spin state, as well as the thermal stability of the high-spin

A new method for the synthesis of diamantane by hydroisomerization of binor-S on treatment with sulfuric acid

• Rishat I. Aminov and
• Ravil I. Khusnutdinov

Beilstein J. Org. Chem. 2020, 16, 2534–2539, doi:10.3762/bjoc.16.205

• compounds, an important place is occupied by diamond-like compounds called diamondoids, whose lower representatives belong to the homologous series C4n+6H4n+12. Owing to the rigid structure, diamondoids typically have high thermal stability and high reactivity compared with aliphatic and alicyclic saturated

Host–guest interaction of cucurbit[8]uril with oroxin A and its effect on the properties of oroxin A

• Zhishu Zeng,
• Jun Xie,
• Guangyan Luo,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2020, 16, 2332–2337, doi:10.3762/bjoc.16.194

• involve three main intermolecular forces: a hydrophobic effect, hydrogen bonding and ion–dipole interactions at the carbonyl portals [7][8][9]. The high thermal stability [10], ease of synthesis [11], general absence of cytotoxicity or toxicity [12][13] and their good molecular recognition and binding

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• substantial delocalization of charges in this direction (Tables S2 and S3, Supporting Information File 1). Thermal properties The thermal stability is quite important for NLO chromophores when using them in electro-optic materials. Therefore, we conducted a thermogravimetric analysis to understand whether the

• residues on the surface of the dyes. Again, the results showed that no dye underwent more than one dissociation step. All dyes dissociated at the very first step but in a nonuniform manner. Regardless, all dyes showed good thermal stability up to around 250 °C, while dye 12, as the least thermally stable

• dye, started to dissociate at around 310 °C. The Schiff base-based dyes had higher thermal stabilities than the dyes 3–7 having a free amino group. The highest thermal stability was observed for dyes 10–12; their rapid degradation values were above 300 °C. Conclusion In summary, we successfully

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• examined first by means of the thermal denaturation method. Various double-stranded DNA or RNA are known upon heating to dissociate into two single-stranded polynucleotides at a characteristic well-defined temperature (Tm value). A non-covalent interaction of small molecules usually increases the thermal

• stability of the ds-polynucleotide, consequently causing an increase of the denaturation temperature (∆Tm). This ∆Tm value can be related to the various binding modes of a small molecule to DNA/RNA [39]. The studies with poly(dG-dC)2 were not possible due to the high melting temperature of >100 °C. As shown

Regiodivergent synthesis of functionalized pyrimidines and imidazoles through phenacyl azides in deep eutectic solvents

• Paola Vitale,
• Luciana Cicco,
• Ilaria Cellamare,
• Filippo M. Perna,
• Antonio Salomone and
• Vito Capriati

Beilstein J. Org. Chem. 2020, 16, 1915–1923, doi:10.3762/bjoc.16.158

• the para-position delivered the expected adduct 3k/3k' in 32% yield even by prolonging the reaction time to 16 h, most probably because of the poor solubility in the eutectic mixture and/or the higher thermal stability towards the loss of N2 (vide infra) of the corresponding phenacyl azide 2k as it is

• between 180 °C and 240 °C [35]. The investigation of the thermal stability of phenacyl azides 2 led to the fortuitous discovery of the competitive formation of a different heterocycle. Indeed, while phenacyl azide (2a) was stable per se in a ChCl/Gly mixture after stirring at rt for 12 h, a new

• is an ongoing synthetic endeavor as these scaffolds are ubiquitous motifs in many biologically active compounds and pharmaceuticals. In this context, in the last decades, the so-called deep eutectic solvents (DESs) have received an increasing attention due to their biodegradability, high thermal

On the hydrolysis of diethyl 2-(perfluorophenyl)malonate

• Ilya V. Taydakov and
• Mikhail A. Kiskin

Beilstein J. Org. Chem. 2020, 16, 1863–1868, doi:10.3762/bjoc.16.153

• to be one of the most powerful tools for fine tuning of chemical and physical properties [19][20]. For example, thermal stability, solubility, metabolic and oxidative stability, lipophilicity, membrane permeability, complexing ability, acid-base, and many other properties can be modified in a broad

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

• heteroaromatic fulgides revealed significant advantages of the latter for applications as molecular switches and optical information storage systems [5][10]. These include higher thermal stability, longer lifetimes of the photocolored forms and higher yields of the photocoloration reactions and better

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• LEDs, which could be problematic when scaling up. Additionally, the attrition of the free floating TiO2@WLE spheres, leading to potential damage or leaching of the TiO2 layer, was not investigated. The excellent chemical and thermal stability of metal alloys makes them ideal supports for applications