Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• acetone (4) and formaldehyde (35) in initiating the photografting in an aqueous solution. The maximum extent of grafting was observed for 10 wt % of 36. The concentration of 42 also affected the extent of photografting. The extent of grafting increased with the increase of the monomer up to 2 mol/L and

• carried out, indicating that the polymerization of MAA (42) was mainly induced by photoinitiation by the aliphatic ketones 44 or formaldehyde (35), rather than by self-initiation of the monomer. Furthermore, oxygen was shown to strongly inhibit the photopolymerization, and an increase in the UV intensity

• increased the percentage of conversion and the polymerization rate. Finally, the percentage of conversion decreased, whereas the polymerization rate increased with an increase of the initial monomer concentration since an increase in the concentration of the monomer led to MAA (42) absorbing more energy

Towards triptycene functionalization and triptycene-linked porphyrin arrays

• Gemma M. Locke,
• Keith J. Flanagan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2020, 16, 763–777, doi:10.3762/bjoc.16.70

• band positions were seen for the symmetric zinc dimer 9, the unsymmetrical dimer 16 and the zinc monomer 14 at 431 (23202), 432 (23149) and 433 (23095) nm (cm−1) in CHCl3, respectively (Figure 6). A similar Soret band for both the dimer and monomer 9 and 14 suggested that the two subunits in the dimer

• bands observed for the zinc dimer and monomer had low full-width at half-maxima (FWHM) of ≈26 nm (3.85 × 105 cm−1), i.e., a narrow band, the zinc-nickel dimer 16 exhibited a high FWHM of ≈50 nm (2 × 105 cm−1), potentially caused by overlapping of the nickel and zinc porphyrin Q bands which could be due

• dimers and 8 nm (1.25 × 106 cm−1) for the monomer. The difference in properties of the unsymmetric zinc-nickel dimer 16 is observed significantly more in the corresponding fluorescence emission spectrum (Figure 7). The emission observed for the zinc monomer and dimer, 14 and 9, respectively, was

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• proceeded well with heterocycle-containing chlorides such as 2-chloro-5-(chloromethyl)thiophene (4e), leading to 2-aminoethyl acetate product 3k in 66% yield which has potential as bifunctional monomer for polymerization. Furthermore, oxazole derivative 2,4,4-trimethyl-4,5-dihydrooxazole (2b) was also

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• molar masses and narrow molecular weight distributions. These techniques allow linear increase of molar mass by time and monomer conversion and low dispersity (principally between 1.2 to 1.5). The most common methods of controlled radical polymerization are namely the nitroxide-mediated radical

• metal ions. In this process, basically, in the presence of photoactive materials (PAs) such as photoinitiators, photosensitizers or photoredox catalysts, the photoexcitation of a photoredox system results in formation of reactive radicals. Those reactive radicals add monomer and the polymerization

• presented for in situ generation of Cu(I) to initiate the polymerization with the alkyl bromide. In this system, the Cu(II) complex was exposed to UV light to form Cu(I) which can react with alkyl halide resulting in generation of reactive radicals and Cu(II), Scheme 9. Those reactive radicals add monomer

Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• . Results and Discussion Initial attempts to polymerize iodoindole monomer 1 using the reported conditions (Scheme 1) produced oligomers with an unanticipated coupling pattern in good yield (87%, Figure 1, Supporting Information File 1, Figure S3). The 1H NMR signals from the C2-H, C3-H on the pyrrole ring

• for a radical mechanism. Moreover, the observed behavior appears to be common between the iodoindole monomer and iodobenzene/indole system, rather than a phenomenon unique to an electron-rich iodoindole. The growing evidence for a phenyl radical in the catalytic cycle is in contrast to the typically

• that proceed under mild conditions, improving energy requirements and scalability. Work is ongoing to leverage this insight into new direct arylation methods utilizing palladium-involved radicals. 1H NMR (500 MHz, CDCl3) of (a) 5-iodo-1-octylindole monomer (b) PIn prepared according to conditions in

Formal preparation of regioregular and alternating thiophene–thiophene copolymers bearing different substituents

• Atsunori Mori,
• Keisuke Fujita,
• Chihiro Kubota,
• Toyoko Suzuki,
• Kentaro Okano,
• Takuya Matsumoto,
• Takashi Nishino and
• Masaki Horie

Beilstein J. Org. Chem. 2020, 16, 317–324, doi:10.3762/bjoc.16.31

• a monomer. Nickel-catalyzed polymerization of bithiophene with substituents at the 3-position, including alkyl-, fluoroalkyl-, or oligosiloxane-containing groups, afforded the corresponding copolymers in good to excellent yield. The solubility test in organic solvents was performed to reveal that

• to afford the regioregular polythiophene in which 2,5-dihalo-3-substituted thiophene 1 is employed as a monomer precursor, converting to the corresponding organometallic monomer by a halogen−magnesium exchange reaction with a Grignard reagent. The employment of 1 leading to polythiophene has been

• shown to proceed in a dehalogenative manner [3]. We have recently shown that the generation of the organometallic monomer species can alternatively also be achieved by deprotonation, using 2-halo-3-substituted thiophene 2 or 3 with a bulky magnesium amide Knochel–Hauser base (TMPMgCl⋅LiCl) [7], followed

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

• ]. Noteworthy, depending on the nature of the bidentate ligand used, the corresponding copper complex could be isolated as monomer or dimer, and both were air-stable. Among the new complexes, the reactivity of [(bpy)CuSeCF3]2 in trifluoromethylselenolations was thoroughly investigated using a large panel of

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• identify possible primary photoprocesses (Figure 7A). The initial maximum of the monomer 3b decreased substantially by approximately half within a second, whereas further reaction was indicated by the appearance of the absorption maximum of 4b at 317–331 nm. Notably, no additional intermediate absorption

• cyclobutane 4b at 315 nm in H2O, the monomer 3b formed, as indicated by the development of its characteristic absorption band (Figure 7B). After 30 min, the reaction was almost complete, however, dimer 4b still remained in solution in the photostationary state. Interactions of the photodimer 4b with DNA The

• absorption and CD spectroscopy (Figure 10). In the course of the photoreaction, the formation of 3b was indicated by the emergence of its characteristic long-wavelength absorption band, whose shape and shift matched its DNA-bound form. The association of the released monomer 3b with DNA was also clearly

Carbazole-functionalized hyper-cross-linked polymers for CO₂ uptake based on Friedel–Crafts polymerization on 9-phenylcarbazole

• Dandan Fang,
• Xiaodong Li,
• Meishuai Zou,
• Xiaoyan Guo and
• Aijuan Zhang

Beilstein J. Org. Chem. 2019, 15, 2856–2863, doi:10.3762/bjoc.15.279

• polymers (HCPs), a series of 9-phenylcarbazole (9-PCz) HCPs (P1–P11) has been made by changing the molar ratio of cross-linker to monomer, the reaction temperature T1, the used amount of catalyst and the concentration of reactants. Fourier transform infrared spectroscopy was utilized to characterize the

• structure of the obtained polymers. The TG analysis of the HCPs showed good thermal stability. More importantly, a comparative study on the porosity revealed that: the molar ratio of cross-linker to monomer was the main influence factor of the BET specific surface area. Increasing the reaction temperature

• outstanding porous properties. Studies of the effects on porosity of HCPs are significant, but almost all investigations focused on the role of monomer length and geometry on the porosity [6][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Researchers have synthesized a series of carbazole-based

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• analogue of the formula [Fe{C5H4COO(CH2)3 C≡}2]2 in a ratio of approximately 4:1. Related NMR spectra can be found in Supporting Information File 1 (Figures S9 and S10). Separation of the monomer 2b could be achieved with column chromatography on silica gel with a yield of 53%. The ring-closed dimer

• remained in a mixture with excess monomer. Single crystals of compound 2b suitable for X-ray diffraction analysis could be obtained at room temperature from a DCM or CDCl3 solution layered with hexane, respectively. An ORTEP drawing of 2b is shown in Figure 6. The ferrocenophane crystallises in the

In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization

• Lei Zhang,
• Greta Linden and
• Olalla Vázquez

Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243

• , 12-mer long sequences are a suitable starting point for our preliminary tests. An overview of all the sequences of this study can be found in Table 1 and Table 2. Contrary to the previous synthetic approach of azobenzene-containing PNAs [35][36][41], in which the preformed monomer building block was

• , the large separation between the n → π* bands of the trans and the cis-forms (Δλ = 69 nm; Figure S24, Supporting Information File 1) did not lead to the quasi-quantitative conversion for the cis-isomer, as for the photoswitchable PNA monomer 1 and the molecular transducer [43][46]. This slightly lower

• cis-form did not show any decomposition under these conditions (Figure S27C, Supporting Information File 1), unlike when the oF4Azo was grafted onto a pyrrole scaffold [48]. Next, we explored if the inclusion of oF4Azo as monomer surrogate within the PNA sequence could affect its hybridization to a

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

• Anniina Kiesilä,
• Jani O. Moilanen,
• Anneli Kruve,
• Christoph A. Schalley,
• Perdita Barran and
• Elina Kalenius

Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241

• , Supporting Information File 1). This ion further dissociates to a neutral monomer and to the [1 − 2H + Me4N]− ion, which can only result from two HA eliminations and dissociation of the H-bonded capsule. Elimination of two HA molecules and formation of [1 + Me4N − 2H]− would be unexpected from a complex with

• ) without (PBE0/def2-TZVP) and with (PBE0-D3/def2-TZVP) dispersion correction because in the gas phase dispersion plays an important role in the formation of supramolecular complexes [24][25][26][27][28][29][30]. Conformational analysis was first performed for both tautomers of the monomer to ensure that

• region showing dimeric ions. Calculated ESP surfaces (in au) superimposed on the total electron density (0.004 au) for 1 and 2: a) monomer, bottom view b) monomer, side view c) monomer, top view, d) dimer, side view and e) dimer, bottom view. Red, blue and green surfaces indicate negative, positive and

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• synthase CotB2wt·Mg2+3·F-Dola in the closed, active conformation (PDB-ID 6GGI; [37]). (A) The two monomers of CotB2 are shown in cartoon representation with the α-helices drawn as cylinders and colored in light brown. One monomer of CotB2 is shown in gray surface representation. The location of the

• cleaved diphosphate is shown in orange. (B) View of panel A rotated by 45°. For clarity, one monomer has been removed. The view is into the active site of CotB2. Conformational changes of CotB2 upon ligand binding. Superposition of CotB2’s open (teal), pre-catalytic (black, CotB2wt·Mg2+B·GGSDP), and fully

Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses

• Anne-Marie Caminade,
• Artem Zibarov,
• Eduardo Cueto Diaz,
• Aurélien Hameau,
• Maxime Klausen,
• Kathleen Moineau-Chane Ching,
• Jean-Pierre Majoral,
• Jean-Baptiste Verlhac,
• Olivier Mongin and
• Mireille Blanchard-Desce

Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221

• bearing 24 fluorophores, compared to 1,400 GM for the corresponding monomer and 780 GM for the quantum dot QD518 (CdSe) [45]. In both previous cases, an essential additive effect was observed, depending on the number of fluorophores grafted to the dendrimers. However, an influence of the structure of the

• derivatives grafted on the surface of phosphorhydrazone dendrimers. In this case, a β-diketone functionalized by a phenol was first grafted on the surface of the dendrimer [47], then BF3 was added to obtain the dioxaborines (Scheme 3). Monomer, dimer, and all generations of the dendrimer from zero (6 terminal

• water-soluble dumbbell-like dendrimers retains a similar TPA response as that of the model monomer in ethanol, as shown by σ2 values of 104 GM for G1, 119 for G2, and 127 for G3, in water [56]. The same type of synthetic method was applied to another TPA fluorophore functionalized by two phenols, but

Genome mining in Trichoderma viride J1-030: discovery and identification of novel sesquiterpene synthase and its products

• Xiang Sun,
• You-Sheng Cai,
• Yujie Yuan,
• Guangkai Bian,
• Ziling Ye,
• Zixin Deng and
• Tiangang Liu

Beilstein J. Org. Chem. 2019, 15, 2052–2058, doi:10.3762/bjoc.15.202

• aspartate-rich motif, 276NSE/DTE triad, 366RY dimer and 230R monomer (Figure S1, Supporting Information File 1) [29][30][31]. Furthermore, in a phylogenetic analysis (Figure 2), Tvi09626 belonged to Clade V of Class I terpene synthases. In previous studies, terpene synthases have been studied in the genus

Morphology-tunable and pH-responsive supramolecular self-assemblies based on AB₂-type host–guest-conjugated amphiphilic molecules for controlled drug delivery

• Yang Bai,
• Cai-ping Liu,
• Di Chen,
• Long-hai Zhuo,
• Huai-tian Bu and
• Wei Tian

Beilstein J. Org. Chem. 2019, 15, 1925–1932, doi:10.3762/bjoc.15.188

• the characteristic signals for BM and propargyl groups in 1H NMR spectrum (Figure S1B-c, Supporting Information File 1), accompanied with the GC–MS results (156.1), indicated the successful preparation of BM-Alk. Finally, the targeted monomer β-CD-BM2 was synthesized through the click reaction between

• spectrometry was 1497.5266 [M + H+], which was in accordance with the theoretical value of 1496.5236. On the basis of the above results, AB2-type host–guest-conjugated amphiphilic monomer β-CD-BM2 has been successfully synthesized. Supramolecular self-assembly behavior of β-CD-BM2 The morphology of the self

• -loaded FSSAs could be considered to deliver and release DOX in cancer cells. Conclusion In summary, an AB2-type host–guest-conjugated amphiphilic monomer, β-cyclodextrin-benzimidazole2 (β-CD-BM2), was successfully prepared to construct pH-responsive supramolecular self-assemblies. On the basis of the pH

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• assignment of the monomer molecules, consequently, its absorption maximum should be blue shifted compared to the monomeric species. If we assume that in ethanol or in dimethylformamide only the monomeric keto form is present, the blue shift of the absorption in acetonitrile indicates that the keto form here

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• lines); c = 10 µM in all cases. Band assignment (when possible): M, monomer; H, H-aggregate; J, J-aggregate. Representative absorption spectra of the distyryl dyes (c = 10 µM in MeOH) demonstrating the influence of the molecular structure on the optical properties. A) Variation of Ar groups. B

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• investigated in the mouse model using ovalbumin as an antigen. Their activities were compared to the previously described mannosylated adamantane-containing desmuramyl peptide and peptidoglycan monomer. Tested compounds exhibited adjuvant activity and the strongest enhancement of IgG production was stimulated

• of the peptidoglycan monomer (PGM, Figure 1) which is used in this work. PGM is a well-defined and characterized disaccharide pentapeptide, β-ᴅ-GlcNAc-(1→4)-ᴅ-MurNAc-ʟ-Ala-ᴅ-isoGln-mesoDAP(εNH2)-ᴅ-Ala-ᴅ-Ala, originating from Brevibacterium divaricatum [8][9]. Peptidoglycans activate macrophages via

Host–guest interactions in nor-seco-cucurbit[10]uril: novel guest-dependent molecular recognition and stereoisomerism

• Xiaodong Zhang,
• Wei Wu,
• Zhu Tao and
• Xin-Long Ni

Beilstein J. Org. Chem. 2019, 15, 1705–1711, doi:10.3762/bjoc.15.166

• Xiaodong Zhang Wei Wu Zhu Tao Xin-Long Ni Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, China 10.3762/bjoc.15.166 Abstract The unique monomer and excimer fluorescence emissions of pyrene were first exploited as distinctly

• , the top–center isomer of G2 within both host-1 and host-2 could be characterized because of the novel monomer and excimer photophysical property of pyrene as fluorophore. As a result, we demonstrated here a novel guest-controlled molecular recognition and stereoisomerism for the first time. Results

• of G1 in host-1 and host-2, despite the clear split of resonances corresponding to the protons on the hosts. A number of studies suggest that pyrene is one of the most useful fluorogenic units, being sensitive to conformational change because of its relatively efficient monomer and excimer emissions

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• of 89.5%. This is comparable to the monomer DPA-6, while P5A-Py with two perylene (Py) pigments grafted on the pillar[5]arene showed a significantly reduced quantum yield of 46.4% vs 78.2% for the monomer Py-6. The oxygen-through-annulus rotation of the phenolic units was inhibited for both compounds

• showed strong absorptions in the visible range and high fluorescence quantum yield, e.g., P5A-DPA showed absorption at 350–410 nm and a quantum yield of 89.5% which is comparable to the monomer DPA-6. On the other hand, P5A-Py with two perylene (Py) pigments grafted on the pillar[5]arene showed intense

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• is lower than in the monomer. Particularly interesting results were observed when the same property of γ-CDP was compared to the corresponding (3-glycidyloxy)propylsilane γ-CD composite (next section). The complexation efficacy of the prepared CDPs is summarised in Table 4. No significant differences

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• subsequent electrochemical characterization of polymer P(DTS) P2 at various scan rates in a monomer-free electrolyte is shown (right). The other examples for P1, P3, and P4 are shown in Supporting Information File 1, Figure S14. After the oxidation of the monomer in the first scan, polymerization starts by

• P1–P4 in a monomer-free electrolyte showed broad and unstructured redox waves typical for conducting polymers reflecting the inhomogeneity of the material containing various electrophoric moieties due to variations in the (conjugated) chain length and conformational issues [52]. As well the

• of heterotriacenes 1–4. Electrochemical properties of poly(heterotriacenes) P1–P4 and film loss after conducting 30 scans in a monomer-free electrolyte solution. Supporting Information Supporting Information File 524: Additional spectral and crystallographic data. Acknowledgements We gratefully

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• Tomas Lizal Vladimir Sindelar Department of Chemistry and RECETOX, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic 10.3762/bjoc.15.124 Abstract The glycoluril monomer is a popular building block in supramolecular chemistry as it is used for the synthesis of versatile host molecules

• simple example of a chromophoric monomer (Scheme 1). The reaction took place under basic conditions using LiH in dry THF [16]. The LiClO4 salt was used originally as a template in order to drive the reaction towards the three-membered macrocycle (n = 3). Later it was found that the salt does not have a

Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• water [56]. Following this water-centered view, we further explored a new type of supramolecular polymeric adhesive based on B21C7 derived low–molecular weight (LMW) monomer, in which the water molecules serve as essential co-monomers to the polymerization process, rather than as solvent [57]. Compared