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

• products from both electron-rich and electron-poor alkenes [56]. The required decomposition of PhHgCF3 (45) can be achieved by refluxing in benzene in the presence of NaI (Scheme 18). In addition to 45, two other organomercury compounds which have been shown to act as sources of difluorocarbene are iodo

• )-monoacetate (S)-80, respectively (Scheme 32). As for the transesterification, a high yield (96.5%) and enantioselectivity (91.3% ee) were obtained using lipase PS in benzene. In the case of the deacetylation, the use of Amano PS lipase in acetone gave a high yield (86.2%), enantioselectivity (91.7% ee), and

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

• the carbazole moieties and the central benzene ring; the same torsions are appreciably smaller at 45.6o and 69.6o for the molecule 2,4-2CzTRZ where one of the carbazole donors is situated at the para position and another one situated at the ortho position [20]. Compound 2,6-2CzTRZ possessed a very

• D–A–D (Type I) molecules containing two carbazole donors disposed each ortho to the acceptor group, while the second family consists of five carbazole donors substituted about a central benzene ring and the sixth position occupied by the acceptor moiety (Type II). Adachi et al. have shown that

• located on the central benzene ring and the acceptor group while the HOMOs are mainly localized on the carbazoles, thereby leading to small ΔESTs. The calculated ΔESTs for 2CzSCF3/2CzSF5 are 0.22 eV and 0.07 eV, respectively, which are comparable to the calculated results for 2CzBN (0.18 eV) and 2CzTRZ

Facile preparation and conversion of 4,4,4-trifluorobut-2-yn-1-ones to aromatic and heteroaromatic compounds

• Takashi Yamazaki,
• Yoh Nakajima,
• Minato Iida and
• Tomoko Kawasaki-Takasuka

Beilstein J. Org. Chem. 2021, 17, 132–138, doi:10.3762/bjoc.17.14

• slowdown of the reaction rate when tert-butylamine was employed, which was considered to be a reflection of the sensitivity of ynones 2 towards steric hindrance. Because appropriate conditions for the initial Michael addition reactions were thus determined, further conversion to the benzene derivative 4aa

Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders

• David Straßburger,
• Svenja Herziger,
• Katharina Huth,
• Moritz Urschbach,
• Rainer Haag and
• Pol Besenius

Beilstein J. Org. Chem. 2021, 17, 97–104, doi:10.3762/bjoc.17.10

• case of the C3-symmetric amphiphile I, the readily available benzene-1,3,5-tricarboxylic acid (trimesic acid) was chosen as the branching unit. In the final amidation reaction, the efficient PyBOP-mediated coupling was carried out using an excess of the peptide amphiphile. Finally, the target compound

Circularly polarized luminescent systems fabricated by Tröger's base derivatives through two different strategies

• Cheng Qian,
• Yuan Chen,
• Qian Zhao,
• Ming Cheng,
• Chen Lin,
• Juli Jiang and
• Leyong Wang

Beilstein J. Org. Chem. 2021, 17, 52–57, doi:10.3762/bjoc.17.6

• FTIR (fourier transform infrared) spectra. UV–vis absorption spectra of rac-TBPP/DGG co-gels exhibited a strong absorption band at 333 nm, assigned to the conjugated structure of benzene and pyridine in the rac-TBPP (Figure 3a). However, a red-shift broaden absorption band situated at 372 nm appears in

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• , MeCN, 4A MS, rt, 80%; iii) HC≡CLi.H2NCH2CH2NH2 (5 equiv), THF, 40 °C, 88%; iv) HCl/MeOH, then HC(OMe)3, 93%; v) Lindlar catalyst, H2, MeOH, 92%; vi) Grubbs catalyst 57 (0.15 equiv), benzene, 50 °C, 99%; vii) OsO4, NMO, MeCN/H2O, 97%; viii) TBDMSOTf, Et3N, CH2Cl2, 98%; ix) 1. CS2, NaH, MeI, THF; 2. AIBN

• , Bu3SnH, benzene, reflux, 82% over two steps; x) 1. TBAF, THF; 2. Li.H2NCH2CH2NH2, 90% over two steps; xi) PCC, CH2Cl2, 77%. Synthesis of (−)-adaline (1) and (−)-euphococcinine (2). Reagents and conditions: i) 1. BuLi, t-BuOK, TMEDA, pentane, −78 °C to −20 °C; 2. RI, THF; 3. H3O+; 44% (R = n-C5H11) and 61

The fluorescence of a mercury probe based on osthol

• Guangyan Luo,
• Zhishu Zeng,
• Lin Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 22–27, doi:10.3762/bjoc.17.3

• the two aromatic rings so that the protons Hf, Hh, and Hi on the branched chain were in the shielding region of the benzene ring and their signals shifted to a higher field. When the protons Hh and Hi of the two methyl groups were in the shielding region of the aromatic ring, the chemical shifts moved

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

• ). Keywords: azine-fused helicenes; carbazole-based [6]helicenes; helical structures; Introduction [n]Helicenes are polycyclic aromatic molecules with nonplanar screw-shaped helical skeletons formed by n-ortho-fused benzene or other aromatic rings. Their helical structure is a consequence of the steric

• ]. It is well-known that the inner helix and outer helix C–C bonds of helicenes differ in their length [9]. Deviations of some of them from the standard aromatic C–C bond of benzene (1.393 Å) are significant. The length of the inner helix C–C bonds of [6]helicene 12 varies from 1.400 to 1.459 Å. On the

• -phenanthro[3,4-c]carbazole). The interplanar angle between the two terminal benzene rings of the latter is equal to 56.7°, whereas the same value for the pyridine-fused analog is 62°. The pyrazine-fused [6]helicene demonstrates intermediate helicity (52.8°). In the case of the quinoxaline-fused analog the

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• 2-ethynylthiophene, did not undergo the reaction to form 2r and 2s. Internal aromatic alkynes were tolerated and generated the desired products 2p and 2q in moderate yield. Aliphatic alkynes, such as (prop-2-yn-1-yl)benzene and (but-3-yn-1-yl)benzene, afforded the corresponding products in an

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• the real extrusion of CO in diaryl ketones [48][49] or of SO2 in diaryl sulfones (Scheme 1c) [50]. Nevertheless, a recent publication demonstrated that a metal-free photoextrusion was feasible when starting from benzene sulfonamides I (Scheme 1d, path a) [51]. Following the same approach, sparse

• photoextrusion from benzene sulfonamides I and phosphonates II, and e) photoextrusion from diaryl- (III) and triaryl (IV) phosphates. Metal-free photochemical synthesis of biaryls 2 and 4. Photoreactivity of aryl phosphates 1 and 3 in protic media. Optimization of the reaction conditions. Emission data of

Ultrasound-assisted Strecker synthesis of novel 2-(hetero)aryl-2-(arylamino)acetonitrile derivatives

• Emese Gal,
• Luiza Gaina,
• Hermina Petkes,
• Alexandra Pop,
• Castelia Cristea,
• Gabriel Barta,
• Dan Cristian Vodnar and
• Luminiţa Silaghi-Dumitrescu

Beilstein J. Org. Chem. 2020, 16, 2929–2936, doi:10.3762/bjoc.16.242

• , ferrocene or benzene units was screened by the Salmonella mutagenicity assay (Ames test) [28] using S. typhimurium TA98 and TA100 strains. Results and Discussions Ultrasound-assisted synthesis The Strecker reaction between (hetero)aromatic aldimines and TMSCN in poly(ethylene glycol) (PEG)–water medium [18

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• typical procedure 2 starting with (nitromethyl)benzene (274 mg, 2.00 mmol) and 2-picolylamine (12, 108 mg, 1.00 mmol), yield 12% (24 mg, 0.12 mmol). Mp 108–110 °C (lit. [36] mp 105–110 °C); Rf 0.51 (EtOAc/petroleum ether 1:1, v/v); 1H NMR (400 MHz, DMSO-d6) δ 8.44 (d, J = 7.2 Hz, 1H, 5-H), 7.83 (d, J

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

• stretching vibration of the –OH group in the skeleton of LS [16]. The tiny peak at approximately 2900 cm−1 was assigned to the stretching vibration of the −CH2− moiety. The characteristic peak of the aromatic benzene ring appeared at about 1500 cm−1 [17]. The vibration bands at 1000−1200 cm−1 were attributed

• were shown in Scheme 1. Aldehydes 2 with different functional groups on the benzene ring could react smoothly with compounds 1a and 3a, producing the corresponding 3,4-fused tricyclic indoles 4b–d with yields ranging from 46% to 64%. o-Anisaldehyde, with steric-hindrance effect, also reacted

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• replacement of sulfur by nitrogen atoms in the tetra- and hexacyclic systems leads to a red-shift in absorption, a decrease in oxidation potential and energy gap. On the other hand, the replacement of a thiophene ring by benzene leads to the opposite effects. Keywords: Buchwald–Hartwig amination; Cadogan

• the results for the whole series of S,N-heteroacenes, we found that replacement of sulfur by nitrogen atoms in the tetracyclic systems leads to a red-shift in absorption, a decrease in oxidation potential and energy gap. On the other hand, the replacement of a thiophene ring by benzene leads to the

Activation of pentafluoropropane isomers at a nanoscopic aluminum chlorofluoride: hydrodefluorination versus dehydrofluorination

• Maëva-Charlotte Kervarec,
• Thomas Braun,
• Mike Ahrens and
• Erhard Kemnitz

Beilstein J. Org. Chem. 2020, 16, 2623–2635, doi:10.3762/bjoc.16.213

• HSiEt3 as a hydrogen source to produce, in the presence of benzene as the solvent, Friedel–Crafts products as main compounds [47]. In contrast, the hydrodefluorination products were generated in the absence of benzene. Thermodynamically, the generation of strong H–F, Al–F, or Si–F bonds can enforce an

• Friedel–Crafts products (Scheme 1) [16]. The activation of fluoropentane was achieved using a modified ACF, loaded with germane or silane [39]. When silane was immobilized at the surface of ACF in the presence of benzene, Friedel–Crafts products were again generated. In comparison, when ACF was loaded

• previous study, a pulse TA experiment suggested the presence of a strong interaction between benzene and the surface of ACF [38]. This result was further confirmed by 1H MAS NMR spectroscopy. Note, that 10a was activated under mild conditions without the use of an additional hydrogen source, which often

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• benzene rings of the TBTQ core. Even the six resonances of the glucose carbons appear to split into two signals (e.g., at δ = 79.96 and δ = 79.98 ppm. Temperature-dependent 1H NMR spectroscopy of TBTQ-(OG)6 again revealed a similar upfield shift of the triazole resonance as that observed for the precursor

• exhibits an emission maximum peak at 329 nm upon excitation at 294 nm. This emission band is probably due to the formation of the ground-state dimer by interaction between the benzene rings upon excitation or excimer emission caused by the interaction between the aromatic rings [41][43]. As the

• -fullerene can be embedded between the six arms of TBTQ-(OG)6 and the distance between the center of one benzene ring of the host and the closest five-membered ring of the guest was calculated to be 3.224 Å. The distances between the center of a triazole ring of TBTQ-(OG)6 and the adjacent five and six

NMR Spectroscopy of supramolecular chemistry on protein surfaces

• Peter Bayer,
• Anja Matena and
• Christine Beuck

Beilstein J. Org. Chem. 2020, 16, 2505–2522, doi:10.3762/bjoc.16.203

• groups of Lys and Arg, often combined with a moiety that cradles the hydrophobic portion of the aliphatic side chain. Supramolecular tweezers consist of alternating benzene and norbornadiene units and thread the side chain of Lys or Arg into their aromatic cavity. In addition, an ion pair interaction is

• formed between the charged head group of the encapsulated amino acid and one of the phosphate moieties attached to the tweezer’s central benzene ring [5]. Supramolecular tweezers have not only proven to be interesting tools to modulate protein–protein interactions [6][7], reverse amyloid fibril formation

A proposed sustainability index for synthesis plans based on input provenance and output fate: application to academic and industrial synthesis plans for vanillin as a case study

• John Andraos

Beilstein J. Org. Chem. 2020, 16, 2346–2362, doi:10.3762/bjoc.16.196

• , toxicological, and safety-hazard impacts of solvents used in reaction, work-up, and purification procedures. It is defined using an overall solvent index (OSI) that scales between 0 and 12 spanning the benign solvent water to the non-benign solvent benzene. Equation 14 and Equation 15 show the explicit

• descending order of impact according to OSI values given in Table 1: benzene (12.000), aniline (10.350), toluene (10.150), nitrobenzene (10.130), cyclohexane (8.777), diethyl ether (8.421), acetic anhydride (8.309), petroleum ether (7.734), ethyl acetate (7.597), N,N-dimethyltoluidine (7.592), methyl tert

• starting material can be found, is to trace to a non-renewable starting material (i) that is a first generation feedstock such as coal, crude oil, or ores from the earth’s crust; or (ii) whose molecular weight is less than 80 g/mol corresponding to benzene or pyridine starting materials. The third option

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

• (c) and (d), the peaks at 1617.41, 1482.23 and 1451.06 cm−1 due to stretching vibrations of the two benzene rings disappeared, and the peak at 1079.42 cm−1 due to C–O stretching vibrations was obviously weakened in the inclusion complex, which were caused by Q[8]. The mass spectrum of the OA@Q[8

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• ]. Photoreaction of 7a and 7b Irradiation of a degassed solution of 7a,b in benzene at 254 nm for 3–4 h yielded a pale yellow solid of ketene 10a,b (Scheme 5, Table 2) through regioselective photoinduced 1,5-phenyl migration and we did not obtain any 1,2-AS or any other photoproduct. The same ketenes were isolated

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• 1,3,5-tris(bromomethyl)benzene (3) using the flash vacuum pyrolysis (FVP) technique as a key transformation (Scheme 1) [30]. As can be seen from an inspection of Scheme 1, they began their journey with the coupling reaction of 3 with 3-butenylmagnesium bromide in the presence of dilithium

• ′-tetramethylethylenediamine (TMEDA) as shown in the Scheme 1. Having the compound 4 in hand, it was subjected to the cyclization in the presence of boron trifluoride to provide the tricyclohexyl-fused benzene derivative which on further dehydrogenation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) afforded 1,5,9

• sumanene (2), it is not only gifted with three benzylic positions stapled between the benzene rings of the triphenylene system but also possess the bowl-curvature which enables stereoselective functionalization at these valuable positions. Taking the advantage of these benzylic positions, two years later

Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols

• Tatsuya Kumon,
• Miroku Shimada,
• Jianyan Wu,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184

• best of our knowledge, there are no reports on the practical synthesis of disubstituted 2-fluoroalkylated indenols so far. Transition-metal-catalyzed carbocyclization reactions of alkynes with benzene derivatives having a leaving group X (X = Br, I, OTs, B(OH)2) have been widely considered as one of

• (Table 1, entry 12), we explored the substrate scope for the [2 + 3] cycloaddition of various fluoroalkylated alkynes 1 and 2-formylphenylboronic acids 2. The results are summarized in Scheme 2. The substrates 1, having an electron-donating substituent on the benzene ring of the fluoroalkylated alkyne

• , such as t-Bu or MeO, reacted efficiently, leading to the desired fluoroalkylated indenols 3bA and 3cA in 74% and 68% yield, respectively. However, the substrate containing the electron-withdrawing group CO2Et on the benzene ring of 1 showed a lower reactivity in this reaction (see 3dA). The

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 preparation of aroylpyrimidines. In 1995, Yamamoto et al. reported the direct introduction of acyl groups into pyrimidine rings by reacting trimethylstannyl derivatives with acylformyl chlorides in dry benzene under a N2 stream [33]. Results and Discussion During our studies on the synthesis of

Polarity effects in 4-fluoro- and 4-(trifluoromethyl)prolines

• Vladimir Kubyshkin

Beilstein J. Org. Chem. 2020, 16, 1837–1852, doi:10.3762/bjoc.16.151

• the stability of the ground-state amide bond, thereby elevating the rotation barrier [84][95]. Interestingly, the increase of the barrier when going from benzene to water (Δwater/benzene = E≠in water − E≠in benzene) was found larger in 1 compared to 2, whereas in the diastereomeric couple 3 and 4 only

• fluoroprolines, 1 and 2 (Figure 9B). However, in this case, the two arguments, 1) and 2) contradict each other. As a result, it was observed that the rotation in 2 is faster, but only by a small number: 0.4 and 0.5 kJ mol−1 in dichloromethane and benzene, respectively [97] (note that in water the ground-state

• between the diastereomeric species. Indeed, this conclusion was further corroborated by the rotation barrier data, which showed higher Δwater/benzene for the less lipophilic diastereomer, 6 (Table 4). Overall, the effects from fluorination in both diastereomeric compounds, 5 and 6, were found to be weak

One-pot and metal-free synthesis of 3-arylated-4-nitrophenols via polyfunctionalized cyclohexanones from β-nitrostyrenes

• Haruyasu Asahara,
• Minami Hiraishi and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2020, 16, 1830–1836, doi:10.3762/bjoc.16.150

• nitroalkene properties and consequently suppressed the Diels–Alder reaction with 2. It is noteworthy that not only the benzene ring, but also a heteroaromatic ring could be introduced into the nitrophenol framework by using this method (Table 3, entry 5). Conclusion β-Nitrostyrene 1a underwent a Diels–Alder