Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• polymers, such as PDMAPS and its structural analogues [88][89][90][91], and on the other hand, polymers with strong hydrogen acceptor and donor units, like the uncharged PNAGA [92][93][94][95][96], show a pronounced UCST. In contrast, the solubilization process of a polymer with LCST behavior is an

• irradiation as well as by host molecule (α-cyclodextrin) complexation [278]. Due to the high number of proton acceptor/donor sites, ureido-modified copolymers such as poly(allylamine-co-allylurea) are also becoming more and more important. The critical phase transition temperature can often be finely tuned

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• Friedel–Crafts fashion (Scheme 10a) gave 82 with moderate to good product yields, respectively [69][70]. A similar work by Janosik involved strongly basic conditions at low temperature with bis(phenylsulfonyl)sulfide (83) as the sulfur donor (Scheme 10b) [73][74]. Disulfides are also important reagents

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• group on the glycosyl donor and the acceptor for the stereoselective formation of the β(1–3) linkage (Figure 4) [132]. Interestingly, oligomers bearing several 4,6-O-benzylidene groups show anomalously small coupling constants for some of the C-1 hydrogens. NMR [133] and X-ray [134] studies revealed

• glycosylation method was also employed to access different branched structures having β(1–3)- and β(1–6)-linked Glc appendances on a β(1–3) backbone [136]. To date, the longer β(1–3)-glucans [137][138] were obtained using a 2-O-acylated donor, to ensure β-selectivity, followed by deacylation and use of the

• approach was efficient in solid phase as well as in solution phase synthesis. The participating (S)-(phenylthiomethyl) benzyl chiral auxiliary at the C-2 position of the glucosyl donor permitted the solid phase synthesis of a branched pentaglucan having a α(1–3) branch on an α(1–6) backbone [174]. Boron

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

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• and -donor and the corresponding zwitterion i is believed to be decisive for the efficacy of the subsequent reaction, protonation of i by the alcohol resulting in the formation of ion pair ii (Scheme 1) [40]. In turn, the pKa value of the alcohol is another important parameter for the speed of the

• rationalized. Note that although a two-step process is discussed herein, it is also conceivable that the reaction towards ii proceeds via a single transition state involving the Michael acceptor, the Michael donor, and the alcohol. Furthermore, the different nucleophilicity of the generated alkoxides might

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

• recognition of pyrimidines in hypothetical X•T–A or X•C–G triplets is complicated by two problems: 1) pyrimidines present only one hydrogen bond acceptor (C=O in T or U) or donor (-NH2 in C) in the major groove, and 2) the six-membered pyrimidine ring extends further out in the major groove than the five

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• of this kind of reaction is the catalytic use of the hydride donor, in this case phenylsilane (PhSiH3), due to the regeneration of the active metal hydride species in the cycloisomerization mechanism pathway (Scheme 18). The lower cyclization constant for the six-membered ring formation, in

• good yields (Scheme 27A, 72a–j). However, better yields were observed with substrates with aromatic electron-donor substituents (72a and 72i). Other olefin-tethered functional groups were tolerated under the reaction conditions (Scheme 27A, 72k–n), and S-containing imines also delivered the alkylated

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

• the morphology of thin films of the photovoltaic cells. To date, the maximum efficiency of 12.05% has been shown by an OSC based on a composite of a donor polythiophene and an acceptor polymeric dicyanoindanone derivative [13]. Among the derivatives of isoindigo, the leading compounds are polymers 1–3

• , which were used in the design of OSCs as donor components of the active layer. Their power conversion efficiency (PCE) reached more than 8%. The development of an OSC based on low-molecular-weight derivatives of type 4, containing only one isoindigo fragment, also seems promising (Scheme 2). One of the

• simple representatives of symmetric dithiophene derivatives of isoindigos 5a–c (Scheme 3). The constructed solar cells with an active layer based on a mixture of compounds 5 (donor) and PC61BM (acceptor) in a 1:1 ratio showed the dependence of the efficiency on the structure and position of substituents

Chemical synthesis of C6-tetrazole ᴅ-mannose building blocks and access to a bioisostere of mannuronic acid 1-phosphate

• Eleni Dimitriou and
• Gavin J. Miller

Beilstein J. Org. Chem. 2021, 17, 1527–1532, doi:10.3762/bjoc.17.110

• to explore the synthesis of a ᴅ-manno C6-tetrazole thioglycoside donor and examine subsequent installation of C1 phosphate and anomeric linker groups. Results and Discussion An initial route towards a protected C6-tetrazole building block started from known mannuronic acid thioglycoside 1 (Scheme 1

• . Repeated attempts were unable to indicate progress beyond mixtures of 8 and 9 in 35% and 14% yields and the procedure was abandoned, instead reverting to the successful route developed in Scheme 2. The final step towards the synthesis of a fully protected C6-tetrazole glycosyl donor required tetrazole

• for glycosylation of 3-(benzyloxycarbonylamino)-1-propanol and furnished a regioisomeric and anomeric mixture in low yield (34%, with 20% recovered starting material and 18% hydrolysed donor, 3:1, α/β). The β-linked (minor) anomer was identified through 1JC-H coupling constant data (J = 156 Hz

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• compound 6. It is unclear how the denitration product 15 forms. Elimination of the ether 14 to regenerate the enone 6 is straightforward, but reductive denitration is a taxing reaction that normally requires strongly reducing conditions or a single electron donor. There are examples of milder denitrations

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• their relative versatility in areas such as directionality, the tunability of the σ-hole, hydrophobicity, and donor atom size [14]. These traits allow for the design of novel supramolecular architectures which are directive and reproducible, without relying on the hydrogen-bonding functionality which in

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• glycoconjugates [1][2][3][4]. Due to the large diversity of glycosyl donors and acceptors there is no general glycosylation method developed so far. To ensure high yielding, as well as regio- and stereoselective glycosidic bond formation, a proper combination of glycosyl donor and acceptor, protecting and leaving

• We started our study by short screening of the glycosylation conditions in liquid SO2 (Table 1). To avoid a potential cleavage of acid-labile protecting groups and to obtain an easily analyzable reaction mixture, pivaloyl-protected mannosyl fluoride α-1a as a relatively stable disarmed glycosyl donor

• mannosyl fluoride α-1a was achieved and the desired O-mannoside 3a was isolated in a high yield and α-selectivity. Hemiacetal α-4 was isolated as the only side-product formed via glycosyl donor hydrolysis with the water present in commercial SO2 [62]. To note, at lower temperatures (Table 1, entry 1) no

Enhanced target cell specificity and uptake of lipid nanoparticles using RNA aptamers and peptides

• Roslyn M. Ray,
• Anders Højgaard Hansen,
• Maria Taskova,
• Bernhard Jandl,
• Jonas Hansen,
• Citra Soemardy,
• Kevin V. Morris and
• Kira Astakhova

Beilstein J. Org. Chem. 2021, 17, 891–907, doi:10.3762/bjoc.17.75

• [63] (The University of Edinburgh, UK). We analyzed two different fields of view per treatment group for each donor (n = 3). For the analysis, we used the positive cell detection software with the following parameters: detection channel set to DAPI with a requested pixel size of 0.45 µm. Nucleus

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant

• Peter J. Halling

Beilstein J. Org. Chem. 2021, 17, 873–884, doi:10.3762/bjoc.17.73

• prochiral diols. The enzyme reacts with an amino or acyl donor, releasing a first co-product, to give an aminated or acylated enzyme intermediate. This then reacts with the prochiral ketone or diol to generate the chiral products. “Ping-pong, first”. Followed in most lipase or esterase hydrolyses of

• . The decline is less, if there is a higher ratio of D (donor of, e.g., amino or acyl groups) to S, the prochiral starting material (ketone or diol). The higher ratio also increases the equilibrium conversion, of course, and shortens the time to reach it. Hence the product ee values at 95% of the

• hence we can write eeDP as: The ratio of the pseudo-specificity constants here governs the competition between the product PR and the donor D in reacting with the free enzyme. The relative rates will be given by SCRb · PR divided by SCD · D. It makes sense that a large value of this ratio will lead to

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• , Chengdu 610100, China 10.3762/bjoc.17.67 Abstract The reversible, weak ground-state aggregate formed by dipole–dipole interactions between an electron donor and an electron acceptor is referred to as an electron-donor–acceptor (EDA) complex. Generally, upon light irradiation, the EDA complex turns into

• in line with the theme of green chemistry. This review discusses the synthetic reactions concerned with EDA complexes as well as the mechanisms that have been shown over the past five years. Keywords: EDA complex; electron acceptor; electron donor; radical; visible light; Review Introduction

• phenomena based on the electron-donor–acceptor (EDA) complex [1][2][3]. Significantly, a broad absorption peak unrelated to the structure, called charge-transfer band, is typically located in the visible region of the UV–vis spectrum [4], which manifests the color variability of the mixed solution of the

Simulating the enzymes of ganglioside biosynthesis with Glycologue

• Andrew G. McDonald and
• Gavin P. Davey

Beilstein J. Org. Chem. 2021, 17, 739–748, doi:10.3762/bjoc.17.64

• glycolipid or some other oligosaccharide, the nucleotide A is the product of the donor and xB is the acceptor product. The strings can be seen as a compression of the familiar condensed linear IUPAC notation, using a single-letter notation to represent sugars, with upper-case denoting ᴅ, and lowercase, the ʟ

• it is possible to infer that all of the enzymes of the model are all configuration-inverting, rather than configuration-retaining. This inversion of configuration refers to the stereochemistry of the anomeric carbon in the acceptor product, which has the opposite configuration to that of the donor

• monosaccharides, Ax is the nucleotide-sugar donor, and yB the acceptor substrate. The formation of a single branch along a linear chain is described as decoration, where the pattern is (Equation 2). Here we have assumed that [x]y is a substring of the parent acceptor and is a shorthand for *[x]y*B, the asterisks

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• , the structures of 4,4'-diphenylfullerene derivatives synthesized are shown in Figure 11, and a number of diphenylmethanofullerenes 169–177 with electron-withdrawing groups are reported in reference [148] (Figure 12). Publication [149] describes compound 178 containing triphenylamine donor groups

• (Scheme 33). Сoordination of these compounds with ruthenium(II) leads to a donor–bridge–acceptor assembly of complexes with various lengths, 187–189. It is believed [153] that the photophysical and electrochemical properties of the complexes presented are promising for the formation of charge-separated

• photoinduced states for artificial photosynthetic devices, in particular where assemblies are expanded from dyads to triads by including a lateral organic or organometallic donor. The synthesis of a whole series of spiromethanofullerenes was carried out through the stage where tosylhydrazone derivatives were

Amino- and polyaminophthalazin-1(2H)-ones: synthesis, coordination properties, and biological activity

• Zbigniew Malinowski,
• Emilia Fornal,
• Agata Sumara,
• Renata Kontek,
• Karol Bukowski,
• Beata Pasternak,
• Dariusz Sroczyński,
• Joachim Kusz,
• Magdalena Małecka and
• Monika Nowak

Beilstein J. Org. Chem. 2021, 17, 558–568, doi:10.3762/bjoc.17.50

• anticancer drug vatalanib [26][27][28] (Figure 1). On the other hand, aminophthalazinones can be prospective candidates as N- and O-donor ligands to form complexes with biological significant metal ions, such as copper or zinc [29]. Recently, we have demonstrated a strategy for the synthesis of phthalazinone

• with a donor nitrogen atom could result in the formation of complexes following a different way of coordination with the metal ion than described in the literature [41]. The complexing properties of compounds 5i, 6d, and 7 were investigated by mass spectrometry (ESIMS). The spectra were recorded after

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

• potential due to the hydrogen atoms at the exterior (Figure 4). This local charge plays an important role in the interaction of proline with the environment in a protein. For example, when a side chain of an aromatic residue docks onto the proline residue, they engage in a donor–acceptor interaction, while

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

• a strong electron delocalization in the molecule of 8a. To study the nature of the electron delocalization for the structure A, an analysis of the interactions between donor Lewis-type NBOs and acceptor non-Lewis NBOs was performed. It showed that the p-type lone pair on the N4 atom is strongly

• delocalized into vicinal N2–N3* and C5–N5* antibonds, leading to the Lewis structures B and C, correspondingly (Scheme 3). A similar analysis of donor–acceptor interactions for the obtained structures leads to the Lewis structures D and E. Note that the structures B and D with a C5–N5 double bond have only a

• following reasons: in case of chloroform, the solvent can form hydrogen bonds with the nitrogen atoms of the 8a molecule, whereas for methanol and water solutions, the solvent can act as a proton donor, and as a result, compound 8a may exist in the 1,3-di-tert-butyl-5-aminotetrazolium cationic form. To

Coupling biocatalysis with high-energy flow reactions for the synthesis of carbamates and β-amino acid derivatives

• Alexander Leslie,
• Thomas S. Moody,
• Megan Smyth,
• Scott Wharry and
• Marcus Baumann

Beilstein J. Org. Chem. 2021, 17, 379–384, doi:10.3762/bjoc.17.33

• ) as the azide donor to facilitate the generation and immediate use of the intermediate acyl azide that would rearrange to an isocyanate upon heating. Toluene was chosen as a suitable solvent providing good solubility of the acid substrates (1 M) in the presence of triethylamine (1.0 equiv

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• certain extent upon the electron demand in the system to which it is attached”. Thus, despite the strong intrinsic electron-withdrawing character, the trifluoromethyl group was shown to modestly act as a π-electron donor when substituting a carbenium ion. Ab initio calculations were performed to account

• obtained. Similarly, the nature of the aromatic substituent influenced the solvolysis rate, with an observed acceleration for substrates adorned with electron donor substituents and a deceleration for those carrying electron-withdrawing substituents. The Hammett–Brown correlation gave a straight line, with

• the electron-withdrawing CF3 group and the electron donor sulfur atom through a captodative effect. Further oxidative electron transfer produces α-(trifluoromethyl)-substituted sulfonium ion 206, leading to 204a,f after reacting with the solvent. α-(Trifluoromethyl)alkylcarbenium ions Hypothetical

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• -difluorocyclopropanecarboxylic acid derivatives 58 by the Michael addition of ester and amide enolates to 2,4,6-trimethylphenyl 4-bromo-4,4-difluorocrotonate (57) followed by an Et3B-initiated radical cyclization (Scheme 24) [68]. Furthermore, when the sodium salt of dimethyl malonate was used as the Michael donor the

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• Dongyang Chen Eli Zysman-Colman Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK 10.3762/bjoc.17.21 Abstract The trifluoromethyl group has been previously explored as a non-conjugated electron-withdrawing group in donor–acceptor

• thermally activated delayed fluorescence (TADF) emitters. In the present study, we investigate computationally the potential of other fluorine-containing acceptors, trifluoromethoxy (OCF3), trifluoromethylthio (SCF3), and pentafluorosulfanyl (SF5), within two families of donor–acceptor TADF emitters. Time

• electron exchange energy J (Equation 1), which itself is dependent on the electron density overlap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) (Equation 2) [10][11]. Compounds possessing a donor–acceptor (D–A) structure could satisfy the requirements