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

• -type compound (λPL = 521 nm for POZ-DBPHZ) in cyclohexane. These data indicate that the effective length of π-conjugation is not affected by the number of donors, probably due to the right D–A dihedral angle for both compounds in the ground state. In contrary, the slight blue-shift of the PL spectra of

Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• only is environmentally friendly, but also finds significant applications in biological systems (e.g., click reactions, bio-conjugation, and bio-orthogonal chemistry). One of such applications is ligation chemistry, in which “click” chemistry through a [3 + 2] biorthogonal cycloaddition between nitrile

• a further cycloaddition. In addition, the conjugation between the new C=N bond and the enol double bond promotes the enol tautomer formation. This may also explain why the trifluoromethylated 1,3-diketones produced the trifluoromethyl-substituted isoxazoles with lower yields than the methyl

The role of chemistry in the success of oligonucleotides as therapeutics

• Pawan Kumar and
• Tom Brown

Beilstein J. Org. Chem. 2022, 18, 197–199, doi:10.3762/bjoc.18.22

• nucleotides massively improves the drug-like properties of oligonucleotides. However, their efficient delivery to the desired tissue/organ also needs to be addressed. Conjugation of oligonucleotides to GalNAc (N-acetylgalactosamine) has successfully been used for targeted delivery of oligonucleotides (both

Mechanistic studies of the solvolysis of alkanesulfonyl and arenesulfonyl halides

• Malcolm J. D’Souza and
• Dennis N. Kevill

Beilstein J. Org. Chem. 2022, 18, 120–132, doi:10.3762/bjoc.18.13

• standard reaction, the goodness of fit of the data using the Hammett substituent constants will be decreased. For example, for phenols which have a direct conjugation of a developing anion with an appropriate substituent, adjusted σ values are available for these substituents. The above is presented to

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

• different chemoselectivities. 2-Alkylideneoxazolidines and 2-alkyloxazolines are structural isomers and can possibly tautomerize each other. As a more electron-withdrawing group with more electron density on the carbonyl group, a ketone favors the conjugation of the double bond as well as the intramolecular

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

• Tanmoy Halder and
• Somnath Yadav

Beilstein J. Org. Chem. 2021, 17, 2915–2921, doi:10.3762/bjoc.17.199

• for further conjugation to other moieties towards the synthesis of vaccine conjugates by removal of the anomeric PMP group. This has been previously demonstrated by removal of the anomeric PMP group, conversion to a glycosidic donor, and further conjugation to either linkers or amino acids by several

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

• Ettore Crovini,
• Zhen Zhang,
• Yu Kusakabe,
• Yongxia Ren,
• Yoshimasa Wada,
• Bilal A. Naqvi,
• Prakhar Sahay,
• Tomas Matulaitis,
• Stefan Diesing,
• Ifor D. W. Samuel,
• Wolfgang Brütting,
• Katsuaki Suzuki,
• Hironori Kaji,
• Stefan Bräse and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 2894–2905, doi:10.3762/bjoc.17.197

• = 0.62) than the values calculated for ICzTRZ (TDM = 7.9 Debye and f = 0.72). DICzTRZ shows a shallower HOMO at −5.03 eV, reflective of a certain degree of conjugation between the two indolocarbazole moieties, compared to the HOMO of ICzTRZ (−5.19 eV). The LUMO level remains essentially unchanged (−1.76

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

• attributed to a greater electronic conjugation provided by the imine function present in the molecules of the series 3. Photostability and singlet oxygen quantum yield (ΦΔ) assays In order to be efficient for applications in photobiology, organic dyes must be stable when subjected to light irradiation for

Ligand-dependent stereoselective Suzuki–Miyaura cross-coupling reactions of β-enamido triflates

• Tomáš Chvojka,
• Athanasios Markos,
• Svatava Voltrová,
• Radek Pohl and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 2657–2662, doi:10.3762/bjoc.17.179

• bond of vinyl (pseudo)halides during the Suzuki coupling have been published [25][26][27][28][29]. Typically, inversion of configuration occurs on substrates containing a double bond in conjugation with an electron-withdrawing group, such as the carbonyl group in enones [27][30]. We hypothesized that

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• example of the use of conjugation to drive an α-ketol rearrangement. This study elegantly illustrates the synthetic power of α-ketol rearrangements, whose suprafacial migration ensured that the α-ketol moiety present in the target product 31 was installed with correct stereochemistry. Taking inspiration

• reduction in conjugation. Another example of a tandem α-ketol rearrangement was used in the total synthesis of delitschiapyrone A (49), a cytotoxic natural product with previously demonstrated efficacy against several cancer cell lines. The final steps of the synthesis include a Diels–Alder reaction between

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• prior to acid-promoted cyclization cannot be ruled out, since conjugation in the push–pull system should weaken the C=C bond and lower its rotational barrier [20]. Similar enaminone isomerizations have been detected even at room temperature [48]. If thermal isomerization indeed takes place, then one

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• 3,5-dibromoanthranilic acid (1) [61] with cyclohexanone in POCl3 through an adapted reported procedure [62] (Scheme 1). With precursor 2 in hand, we intended to expand the π-conjugation of the tetrahydroacridine core by adding diversely substituted aryl groups using the Suzuki–Miyaura cross-coupling

Post-functionalization of drug-loaded nanoparticles prepared by polymerization-induced self-assembly (PISA) with mitochondria targeting ligands

• Janina-Miriam Noy,
• Fan Chen and
• Martina Stenzel

Beilstein J. Org. Chem. 2021, 17, 2302–2314, doi:10.3762/bjoc.17.148

• at the start of the reaction and after 45 min tuned to 8.3 to allow maximum conjugation efficiency. After removing excess TPP-COOH and coupling reagents via dialysis in Milli-Q water, the particles were adjusted to 4 mg mL−1 and analysed using DLS experiments and TEM microscopy (Figure 1). The

• same conditions as described above. The conjugation product was analysed using 1H and 31P NMR spectroscopy. The 31P NMR spectrum (Figure 2a) shows a peak at 23.07 ppm which belongs to the phosphorus of the triphenylphosphonium moiety. Furthermore, the additional peaks in the region between 7.5–8.2 ppm

• modification. The integration for the peak at the region (g, h and i) increased by 0.26 in number, suggesting that approximately one TPP group per chain was attached. The model reaction using PP3 revealed that the conjugation of TPP-COOH to the polymer proceeded in a quantitative manner and can be used as a

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

• -polyazulene 5 (417 nm) compared to azulene (1, 341 nm) supporting the presence of extended conjugation prevailing in the polymer. The absorption and EPR spectral patterns of 1,3-polyazulene 5 recorded in TFA and H2SO4 were contrasting to each other inferring the varied degree of protonation caused by these

• stability as well. The absorption maxima displayed by polymer 18 (409 nm) in dichloromethane solution was comparable to the above-discussed 1,3-polyazulene 5 (404 nm), however, the long alkyl substituents present at the 6-position of 19 and 20 were disrupting the effective π-conjugation along the polymer

• the polymer backbone. The iminium zwitterion resonance structure (Figure 2) can contribute in extending the conjugation along the backbone of poly[2(6)-aminoazulene] 31 and this property of 31 makes it very different from the well-known polyaniline. The absorption peak positions of the protonated

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

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

• strategy that has been employed to optimize the delivery profile of ASOs, is the functionalization of ASOs with cationic amine groups, either by direct conjugation onto the sugar, nucleobase or internucleotide linkage. The introduction of these positively charged groups has improved properties like

• improved liver targeting [22][23] and ASO–glucagon-like peptide-1 (GLP1) conjugation for improved delivery to pancreatic β-cells [24]. Previously, Menzi et al. reviewed the impact of cationic modifications and conjugations for ONs and siRNAs biophysical and biological activities until 2015 [25]. In this

• review, we focus on important monomeric cationic modifications for ASOs, including locked nucleic acid (LNA) monomers, and their synthesis. Such modifications have been achieved either by direct conjugation to the nucleobase, the sugar or the backbone of nucleotide monomers of such ASOs. In addition, a

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• -economical approach to several tryptophan-containing peptides with significant potential for drug discovery and medicinal chemistry. Positional selectivity was observed at the C2 position due to the presence of the pyrimidine directing group. Interestingly, alkynylative conjugation of tryptophan to a steroid

• peptide–carbohydrate conjugation was achieved using tryptophan-containing peptides 29 and sugar-containing allyl carbonates 30 in chemo- and site-selective manners using a pyridyl directing group. The optimized reaction conditions entailed the use of dimanganese decacarbonyl as the catalyst and sodium

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

• phosphono-PNAs retained the stability against nucleases. In another study, conjugation with glutamine phosphonate or lysine bis-phosphonate amino acid derivatives introduced up to twelve negative charges (phosphonate moieties) into PNAs [91]. The negative charges allowed cationic lipid-mediated delivery of

• ][159][160]. Looking forward, conjugation of PNA with various delivery enhancing compounds, most notably cell-penetrating peptides (CPP) that deliver the conjugates mainly through endocytosis (Figure 11) has become one of the most promising approaches to improving cellular uptake of PNA [161][162

• covalent conjugation of PNA to delivery enhancing compounds. Cell-penetrating peptides derived from natural proteins: The initial success of PNA delivery involved PNA conjugates taken up by receptor-mediated endocytosis. Pardridge and co-workers successfully demonstrated in vivo delivery and blood-brain

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• catalysis. With this precursor in hand, we intended to expand the π-conjugation by introducing two arylethynyl groups by Sonogashira reactions [66][67][68][69]. For the optimization, we studied the reaction of 2 with phenylacetylene (3a) and we obtained the desired product 4a in up to 72% as best yield

• )-9-chloro-5,6,7,8-tetrahydroacridine derivatives via a double Sonogashira cross-coupling method. The arylethynyl groups expand the π-conjugation of the tetrahydroacridine core. The substituents located at the aryl group influenced the photophysical properties of the prepared molecules. In particular

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

• , to date, the volume of publications on the study of the biological activity of isoindigo derivatives has been steadily decreasing. At the same time, the unique properties of the isoindigo structure (planarity, stability, a high degree of conjugation, and electron deficiency) began to attract more and

• characterized by a high short-circuit current (JSC = 13.92 mA/cm2), with a 5-fold better PCE value (Table 3). Expansion of the conjugation chain by introducing additional electron-enriched condensed heterocyclic fragments (see compounds 20 and 21) makes it possible to achieve a PCE of almost 6% (Scheme 13) [31

• of 1:4 showed an efficiency of 7.69% with a D1 content of 15% relative to the D2 weight. It should be especially noted that the efficiency of the cell without isoindigo D1 was 6.91%. To increase the degree of conjugation in the structure of polymeric isoindigo, an introduction of additional aromatic

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

• materials, and as the basis of the study of through-space conjugation [2][8][9][10][11][12][13][14][15][16]. There are fewer studies of [2.2]metacyclophane (2) and its derivatives. This is probably related to a lack availability as well as the reduced interaction between the aromatic rings [17]. But the odd

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

• be considered as a 1,3,5‐triphenylbenzene derivative enjoying with three methylene units clipped in such a manner that all the four benzene rings are in conjugation with coplanar arrangement, resulting strong π–π stacking in addition to the strong electron‐donating ability which in turns provide a

• corresponding desired truxene-based oxazole derivatives (Scheme 6). Additionally, to enhance the conjugation which in turn would undoubtedly tune the properties of the truxene-based heterocyclic systems, we also design and synthesized the benzene-bridged oxazole derivative 25 in three steps (Scheme 7). As can

• possessing red-shift absorption maxima as compared to the parent compound 2, may be due to increased conjugation in these truxene systems with the incorporation of three heterocyclic units in each case (Figure 1). Moreover, the absorption spectrum of compound 16 exhibited slightly red-shifted maxima at ca

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• , specifically because of the decreased electron density at the 9-oxyanion by linear conjugation with the quaternary nitrogen atom [39]. Nevertheless, the reactivity of intermediate 6 is still relatively low, as indicated by the low yields of the Cu2+-catalyzed coupling reaction, thus resembling the parent

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

• hydrogen atom to orient towards anions (chloride) in the vicinity and the 3'-nitrogen lone pair engages in a lp → σ* anomeric effect with the antibonding orbital from the adjacent P–O5' bond (Figure 2A). This conjugation is surmised to cause considerably increased rigidity of the phosphoramidate sugar

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

• -HAIYPRH-NH2 Tat: H-YGRKKRRQRRR-NH2 Modified Tat: dipalmitoyl-Dap-YGRKKRRQRRR-NH2 Peptide conjugation with a lipid reagent The peptides were N-terminally modified on solid support by coupling of Fmoc-Dap(Fmoc)-OH, followed by the coupling of palmitic acid to afford the complete peptide–lipid conjugates