An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(ε-caprolactone)

• Jochen Löblein,
• Thomas Lorson,
• Miriam Komma,
• Tobias Kielholz,
• Maike Windbergs,
• Paul D. Dalton and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2021, 17, 2095–2101, doi:10.3762/bjoc.17.136

• min (Figure 1E) and the intensity of the blue coloration is proportional to reaction time resulting in a complete coating of the PCL fibers after 30 min. The distance between the UV source and the scaffold was varied from 0.5 cm, 1.0 cm, and 1.5 cm (Figure 1F) and, as the intensity decreases inversely

• . However, the authors used UV-C light with an intensity of 0.024 W/cm2 compared to UV-A light with a calculated intensity of 0.079 W/cm2 at a distance of 1.0 cm used in the present study. After SIPGP, a thin, heterogeneous material can be seen spanning large proportion of the pores (Figure 2A and Figure 2B

• spatially resolved polymer identification based on chemical functionalities. A unique peak at 1111 cm−1 was identified and is attributed to backbone stretching of aliphatic chains [ν(C–C)] in PCL. Also, a characteristic band at 829 cm−1 was detected which can be assigned to PHEMA and refers to the

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• photochemical reactivity of NIR dyes in a three-component PIS. Quantitative estimations of the polymerization time of PETIA monomer using a NIR dye/iod/amine 0.1:3:2, w/w/w system upon exposure to a laser diode at 785 nm (0.9 W/cm²), thickness = 1.4 mm, under air and at room temperature. The irradiation starts

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• Abstract This work presents an examination of the selective functionalization of norbornadiene through nitrile oxide 1,3-dipolar cycloaddition/ring-opening metathesis (ROM)/cross-metathesis (CM) protocols. Functionalization of commercially available norbornadiene provided novel bicyclic scaffolds with

• multiple stereogenic centers. The synthesis involved selective cycloadditions, with subsequent ROM of the formed cycloalkene-fused isoxazoline scaffolds and selective CM by chemodifferentiation of the olefin bonds of the resulting alkenylated derivatives. Various experimental conditions were applied for

• the CM transformations with the goal of exploring substrate and steric effects, catalyst influence and chemodifferentiation of the olefin bonds furnishing the corresponding functionalized, fluorine-containing isoxazoline derivatives. Keywords: functionalization; metathesis; nitrile oxide

Volatile emission and biosynthesis in endophytic fungi colonizing black poplar leaves

• Christin Walther,
• Pamela Baumann,
• Katrin Luck,
• Beate Rothe,
• Peter H. W. Biedermann,
• Jonathan Gershenzon,
• Tobias G. Köllner and
• Sybille B. Unsicker

Beilstein J. Org. Chem. 2021, 17, 1698–1711, doi:10.3762/bjoc.17.118

• were brought into pure culture on PDA medium using the same culturing conditions as above. Fresh mycelium was harvested from pure cultures for molecular identification of the morphospecies. Molecular identification of endophytic fungi DNA was extracted from fresh mycelium (approximately 5 cm in

• mycelium reached a diameter of 5 cm (± 0.5 cm). For each fungal species, seven replicates were used with fungus-free petri dishes with PDA medium used as blanks. Volatiles were trapped for 1 h by using four polydimethylsiloxane (PDMS) tubes. To prevent PDMS tubes from touching the mycelium, the tubes were

• (approximately 5 cm in diameter) growing on PDA using the RNeasy® Plant Mini Kit (Qiagen) according to the manufacturer’s instructions. The RNA concentration was assessed using a spectrophotometer (NanoDrop 2000c, Thermo Fisher Scientific). RNA was treated with DNase I (Thermo Fisher Scientific) prior to cDNA

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

• methoxy substituent exhibits a larger red shift of around 40 nm. Based on the absorption and emission spectra, the prepared tetrahydroacridine derivatives possess stokes shifts (wavenumber) ranging from 2400 to 4300 cm−1. Their fluorescence quantum yields range from 0.1 to 0.2 as measured according to a

• were recorded on a Shimadzu 2401 PC spectrophotometer in quartz cuvettes with a path length of 1 cm. Emission spectra were recorded on a Perkin-Elmer LS50B spectrofluorimeter. Theoretical calculations Theoretical studies were realized in vacuum with Gaussian 09 program [72]. The geometry of the

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

• , J = 7.2, 8.5, 13.3 Hz, 1H, H-1b); 13C NMR (126 MHz, CDCl3) δ (ppm) 149.0, 142.2, 139.9, 139.5, 137.9, 137.5, 136.6, 133.3, 133.3, 132.6, 130.1, 129.7, 36.2, 35.1, 35.0, 34.6; IR: 3009, 2928, 1694, 1531, 1516, 1336, 808 cm−1; mp: 158–160 °C; Rf: 0.43 (10% EtOAc, 90% hexane). Data matches previous

• ; ESIMS (m/z): [M]– 264, 252, 223, 151, 89; IR: 3306, 2917, 2850, 1738, 1534, 1261 cm−1; mp: 152–155 °C; Rf: 0.40, (10% EtOAc, 90% hexane). (4(16)Z)-8-Hydroxy-6-nitrotricyclo[9.2.2.14,8]hexadeca-1(13),4,(16),6,11,14-pentaen-5-one (6) 1H NMR (500 MHz, DMSO-d6) δ (ppm) 7.48 (d, J = 8.1 Hz, 1H, H-13), 7.29

• , 2925, 1665, 1535, 1356, 1010, 729 cm−1; mp: 206–213 °C; Rf: 0.25 (20% EtOAc, 80% hexane). (4(16)Z)-8-Hydroxy-7-methoxy-6-nitrocyclo[9.2.2.14,8]hexadeca-1(13),4(16),11,14-tetraen-5-one (14) and (4(16)Z)-8-hydroxytricyclo[9.2.2.14,8]hexadeca-1(13),4(16),6,11,14-pentaen-5-one) (15): To a solution of 6

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• , 1495, 1331, 1279, 1230, 1133, 1100, 921, 716 cm−1; ESIMS (m/z): 365.1 (100, [M + Na]+), 343.1 (12, [M + H]+); Anal. calcd for C18H9F3N2O2: C, 63.16; H, 2.65; N, 8.18; found: C, 63.34; H, 2.63; N, 8.24 (all values are given as percentages). 3a,5,6,7a-Tetramethyl-1-(p-tolyl)-3-(trifluoromethyl)-3a,7a

• , 1379, 1267, 1170, 1118, 1070, 1029, 954, 850, 816, 712 cm−1; ESIMS (m/z): 365.4 (100, [M + H]+); Anal. calcd for C19H19F3N2O2: C, 62.63; H, 5.26; N, 7.69; found: C, 62.76; H, 5.39; N, 7.95. Structures of exemplary benzo- and heteroaromatic fused 1,4-quinone drugs and natural products. X-ray structure

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

• 600 to 4000 cm−1. UV–vis spectra were recorded on a UV-1800 Shimadzu spectrophotometer and the fluorescence spectra were recorded on an Agilent Carry Eclipse spectrofluorimeter. Synthesis of 10,15-dihydro-5H-diindeno[1,2-a:1',2'-c]fluorene (7): Truxene scaffold 7 was prepared according to a literature

• , 149.65, 147.08, 145.20, 137.48, 124.91, 122.66, 117.60, 56.57, 36.44, 26.54, 22.63, 13.71; IR (KBr): 2957, 2925, 2858, 1742, 1594, 1517, 1458 cm−1; MS (m/z): 814.00. Synthesis of 5,5,10,10,15,15-hexabutyl-10,15-dihydro-5H-diindeno[1,2-a:1',2'-c]fluorene-2,7,12-triamine (4): To a 100 mL round bottom flask

• (d, J = 8.1 Hz, 3H), 3.69 (b–NH, 6H), 2.91–2.81 (m, 6H), 1.96–1.87 (m, 6H), 0.94–0.60 (m, 12H), 0.56–0.42 (m, 30H); 13C NMR (75 MHz, CDCl3) δ 155.72, 144.69, 141.19, 138.07, 132.30, 125.41, 113.23, 109.04, 55.05, 36.85, 26.50, 22.95, 13.91; IR (KBr): 3369, 3012, 2953, 2922, 2855, 1619, 1584, 1485 cm

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• ) 3558, 3004, 2965, 2932, 2905, 2837, 1606, 1585, 1512, 1461, 1307, 1250, 1178, 1156, 1085, 1055, 1028, 838, 801, 754 cm−1; 1H NMR (301 MHz, CDCl3) δ 2.42 (s, 3H), 3.76 (s, 3H), 3.82 (s, 3H), 4.19 (s, 1H), 5.23 (s, 1H), 6.83 (d, J = 8.9 Hz, 2H), 6.94 (d, J = 8.9 Hz, 2H), 7.29–7.42 (m, 6H), 7.55 (d, J

• (hexane/EtOAc) to give sulfoxide 2a [1.38 g, 3.34 mmol, 87%, Rf = 0.50 (hexane/EtOAc 1:1)]. Colorless solid; mp 140.2–141.0 °C; IR (ATR) 3063, 3032, 3024, 2955, 2932, 2908, 2837, 1603, 1577, 1506, 1462, 1306, 1246, 1172, 1082, 1049, 1031, 829 cm−1; 1H NMR (399 MHz, CDCl3) δ 2.42 (s, 3H), 3.79 (s, 3H

• , 820 cm−1; 1H NMR (301 MHz, CDCl3) δ 3.83 (s, 6H), 6.87 (d, J = 8.8 Hz, 4H), 7.45 (d, J = 8.8 Hz, 4H); 13C NMR (126 MHz, CDCl3) δ 55.3, 88.0, 114.0, 115.7, 132.9, 159.4; EIMS (m/z, %): 238 ([M]+, 100), 223 (55); HRMS–EI (m/z): [M]+ calcd for C16H14O2, 238.0994; found, 238.0997. Optimized geometries of

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

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

• of this study, which is divided into two parts, the hydrogel denoted as HGCM was utilized as the main substrate for both sections. To prepare HGCM, firstly graphitic carbon nitride was synthesized from the thermal treatment of a cyanuric acid–melamine supramolecular complex (CM) [42]. The resulting

• yellow powder was ultrasonicated in water to obtain a g-CN aqueous colloidal dispersion. The freshly prepared CM/water colloidal dispersion was mixed with water-soluble monomer (N,N-dimethylacrylamide, DMA) and crosslinker (N,N’-methylenebisacrylamide, MBA) followed by the addition of the redox couple

• were characterized via FTIR analysis to elucidate structural footprints of CM embedding and vTA photographing. The broad peak in the range from 3639 cm−1 to 3136 cm−1 corresponds to the hydrogen bonding between carboxyl and hydroxy groups with amide functionality of the hydrogel backbone. Significant

A new glance at the chemosphere of macroalgal–bacterial interactions: In situ profiling of metabolites in symbiosis by mass spectrometry

• Marine Vallet,
• Filip Kaftan,
• Veit Grabe,
• Fatemeh Ghaderiardakani,
• Simona Fenizia,
• Aleš Svatoš,
• Georg Pohnert and
• Thomas Wichard

Beilstein J. Org. Chem. 2021, 17, 1313–1322, doi:10.3762/bjoc.17.91

• following the procedure for in situ MS imaging described by Kessler et al. [19]. Briefly, algal gametes were inoculated to 10 mL medium in 9 cm diameter sterile Petri dishes with a clean and autoclaved glass slide (25 mm × 75 mm) with cavities (Paul Marienfeld, Germany) on the bottom; samples were incubated

Nitroalkene reduction in deep eutectic solvents promoted by BH₃NH₃

• Chiara Faverio,
• Monica Fiorenza Boselli,
• Patricia Camarero Gonzalez,
• Alessandra Puglisi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2021, 17, 1041–1047, doi:10.3762/bjoc.17.83

• , valuable precursors of chiral amines. Experimental Experimental procedure for the reduction in glycerol The desired nitroolefin (0.4 mmol) was suspended in glycerol (4 mL) in a 7 mL vial equipped with a 3.5 cm-long magnetic stir bar. Ammonia borane (12 mg, 0.4 mmol) was added to the suspension at room

• ), dried over Na2SO4, filtered, and the solvent was evaporated under reduced pressure. The crude product was purified by column chromatography (silica as stationary phase; eluent: n-hexane/ethyl acetate). Experimental procedure for the reduction in DES In a 7 mL vial with a 3.5 cm-long magnetic stir bar

• 7 mL vial with a 3.5 cm-long magnetic stir bar, 2.5 g of DES were freshly prepared, ChCl and glycerol (1:2 molar ratio) were mixed, and the mixture was heated at 70 °C for 15 min until it became a colorless liquid. Then, the DES was slowly cooled to room temperature in 15 min. trans-β-Methyl-β

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• * transition, with a shift of the peak to 210 nm when biguanide is protonated. Infrared spectra present three characteristic absorption bands: a sharp absorption peak of medium intensity in the 1150–1170 cm−1 range, a strong band between 1480–1660 cm−1 corresponding to the C=N vibration, and a strong band at

• 3100–3400 cm−1 for the N–H bonds vibrations. NMR spectra record specific signals at 6.8–7.5 ppm for the shifts of the protons and 158–165 ppm for the 13C. Biguanides are good nucleophiles and easily carbonated under ambient conditions. They are stable over a wide range of pH. Often, heating in the

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

• according to the published protocol [66]. Calf thymus DNA (ct DNA, type I; highly polymerized sodium salt; ε = 12824 cm−1 M−1) [67] was purchased from Sigma-Aldrich (St. Louis, USA) and used without further purification. Concentration of ct DNA is given in base pairs (bp). The ct DNA was dissolved in BPE

• : 6.0 mM Na2HPO4, 2.0 mM NaH2PO4, 1.0 mM Na2EDTA; pH 7.0. All buffer solutions were prepared from purified water (resistivity 18 MΩ cm) and biochemistry-grade chemicals. The buffer solutions were filtered through a PVDF membrane filter (pore size 0.45 μm) prior to use. Structures and numbering of

Synthesis and properties of oligonucleotides modified with an N-methylguanidine-bridged nucleic acid (GuNA[Me]) bearing adenine, guanine, or 5-methylcytosine nucleobases

• Naohiro Horie,
• Takao Yamaguchi,
• Shinji Kumagai and
• Satoshi Obika

Beilstein J. Org. Chem. 2021, 17, 622–629, doi:10.3762/bjoc.17.54

• (698 mg, 72%) as a yellow solid substance. 2a: −26.4 (c 1.0, CHCl3); IR (KBr): 2999, 2952, 2837, 1696, 1606, 1509, 1451, 1410, 1297, 1251, 1177, 1155, 1074, 1035 cm−1; 1H NMR (CDCl3) δ 2.00 (s, 3H), 2.80 (s, 3H), 3.48, 3.57 (AB, J = 10.7 Hz, 2H), 3.67 (s, 2H), 3.74 (s, 3H), 3.74 (s, 3H), 4.37 (s, 1H

• 1.0, CHCl3); IR (KBr): 3350, 2971, 2837, 1750, 1712, 1587, 1509, 1444, 1411, 1335, 1284, 1249, 1226, 1176, 1116, 1068, 1035 cm−1; 1H NMR (CDCl3) δ 1.23 (d, J = 6.5 Hz, 3H), 1.25 (d, J = 6.2 Hz, 3H), 2.05 (s, 3H), 2.55–2.66 (m, 1H), 3.05 (d, J = 4.2 Hz, 3H), 3.48, 3.53 (AB, J = 10.8 Hz, 2H), 3.59, 3.74

• were recorded at 10 °C in a quartz cuvette of 1 cm optical path length. The samples were prepared in the same manner as described in the UV melting experiments. The molar ellipticity was calculated from the equation [θ] = θ/cl, where θ, c, and l indicate the relative intensity, sample concentration

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

• –0.97 g⋅cm−3, Tm 130 °C) is a highly crystalline material with a low degree of short chain branching. Owing to the high stiffness, tensile strength, resistance to moisture and gas permeability, it is mainly used in the manufacture of water pipes, toys, beverage bottles, outdoor furniture, housewares and

• electrical cables [138][139]. LDPE (0.91–0.94 g⋅cm−3, Tm 120 °C) is a poorly crystalline material having a high degree of short chain and long chain branching. It is featured by a good flexibility, transparency and high impact strength, which make it suitable for short-term applications, such as films, food

Breakdown of 3-(allylsulfonio)propanoates in bacteria from the Roseobacter group yields garlic oil constituents

• Anuj Kumar Chhalodia and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 569–580, doi:10.3762/bjoc.17.51

• , 7.56 mmol, 30%) as pale yellow oil. TLC Rf 0.44 (cyclohexane/EtOAc 10:3); IR (diamond-ATR) ν̃: 2998 (w), 2952 (w), 2845 (w), 2256 (w), 1730 (m), 1436 (w), 1354 (w), 1240 (w), 1215(w), 1195 (w), 1171 (w), 1139 (w), 1046 (w), 1017 (w), 979 (w), 907 (w), 822 (w), 726 (m), 648 (w), 435 (w) cm−1; 1H NMR

• : 3082 (w), 2950 (w), 2845 (w), 1736 (s), 1634 (w), 1435 (w), 1354 (w), 1277 (w), 1240 (w), 1216 (w), 1172 (w), 1144 (w), 1017 (w), 985 (w), 922 (w), 859 (w), 820 (w), 756 (w), 722 (w), 669 (w), 582 (w), 478 (w), 435 (w) cm−1; 1H NMR (CDCl3, 500 MHz) δ 5.83 (ddt, J = 17.1, 9.9, 7.3, 1H), 5.19 (ddt, J

• ), 1418 (w), 1375 (w), 1331 (w), 1306 (m), 1373 (m), 1259 (m), 1203 (w), 1180 (w), 1131 (m), 1056 (w), 1004 (w), 988 (w), 971 (w), 956 (w), 898 (w), 786 (w), 774 (w), 749 (w), 601 (w), 514 (w), 505 (w), 441 (w) cm−1; 1H NMR (d6-DMSO, 500 MHz) δ 3.63 (s, 3H), 3.37 (t, J = 7.5, 2H), 3.01 (s, 3H), 2.78 (t, J

A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles

• Lucía Rossi-Fernández,
• Viviana Dorn and
• Gabriel Radivoy

Beilstein J. Org. Chem. 2021, 17, 519–526, doi:10.3762/bjoc.17.46

• , showed a weak band at near 1610 cm−1 which could be assigned to the presence of benzaldehyde surface species [53] that could be affecting to some extent the selectivity of the catalyst. The heterogeneous nature of the catalytic process was confirmed by a hot filtration test. For this purpose, under the

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• (surface tension: 72.1 mN m−1 at 20 °C, resistivity: 18.2 MΩ cm). Mass spectra (MS) and HRMS were performed using a JMS-700 spectrometer (JEOL, Japan). RP-HPLC chromatograms were recorded on a Prominence system (Shimadzu, Japan). FTIR spectra were recorded on IRAffinity-1 (Shimadzu, Japan) spectrometer

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• ) cm−1; 1H NMR (500 MHz, CDCl3, 298 K) δ 7.88 (ddd, J = 8.1, 1.2, 0.7 Hz, 1H, CH), 7.87 (ddd, J = 7.9, 1.2, 0.6 Hz, 1H, CH), 7.43 (ddd, J = 8.3, 7.3, 1.2 Hz, 1H, CH), 7.33 (ddd, J = 8.2, 7.2, 1.2 Hz, 1H, CH), 2.67 (s, 3H, CH3) ppm; 13C NMR (125 MHz, CDCl3, 298 K) δ 172.50 (C), 155.17 (C), 135.90 (C

• (cyclohexane/ethyl acetate 1:1); GC (HP-5MS): I = 1200; IR (diamond-ATR) ν̃: 2982 (w), 2927 (w),1695 (m), 1569 (m), 1434 (w), 1374 (w), 1300 (w), 1266 (w), 1213 (m), 1166 (s), 1095 (w), 1033 (w), 986 (w), 961 (w), 800 (w), 727 (w), 687 (w) cm−1; 1H NMR (700 MHz, CDCl3, 298 K) δ 7.04 (d, J = 10.14 Hz, 1H, CH

• = 1177; IR (diamond-ATR) ν̃: 2980 (w), 2925 (w), 1701 (s), 1578 (s), 1444 (w), 1366 (w), 1322 (w), 1297 (m), 1251 (s), 1161 (s), 1095 (w), 1037 (m), 945 (m), 886 (w), 832 (w), 799 (w), 702 (w) cm−1; 1H NMR (700 MHz, CDCl3, 298 K) δ 7.76 (d, J = 14.93 Hz, 1H, CH), 5.68 (d, J = 14.90 Hz, 1H, CH), 4.21 (q

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• studies of cyano group containing products 5a and 5c the cross signals for the C(2’’)–H system were not found using HSQC spectra, excluding the existence of C–H tautomeric forms A. In addition, IR analysis (KBr tablet) indicated absorption bands of cyano groups at 2205 and 2170 cm−1 for product 5a and at

• 2205 cm−1 for product 5c. These results differ from the absorption in the range of 2260–2240 cm−1, which would be characteristic for a cyano group attached to sp3-hybridized carbon [82]. On the other hand, 13C NMR shifts of the C(2’’) position of purine–malononitrile conjugate 5a and ethyl cyanoacetate

• used in the reactions were dried with standard drying agents and freshly distilled prior to use. Commercial reagents were used as received. IR spectra were recorded in KBr tablets with a Perkin–Elmer Spectrum BX FTIR spectrometer (4000–450 cm−1). Wavelengths are given in cm−1. For HPLC analysis an

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF₃)₂CHOH]

• Takeshi Fujita,
• Noriaki Shoji,
• Nao Yoshikawa and
• Junji Ichikawa

Beilstein J. Org. Chem. 2021, 17, 396–403, doi:10.3762/bjoc.17.35

• , 129.5, 129.6, 130.0, 130.7, 131.2, 131.6, 133.8, 134.0, 140.2, 140.9, 141.4; IR (neat) ν: 3055, 3020, 2976, 2883, 1471, 1442, 1433, 1398, 1194, 1130, 1038, 1009, 943, 872, 837, 822, 752, 706, 621, 573, 538 cm−1; HRMS (EI) m/z: [M]+ calcd. for C26H26O4, 402.1826; found, 402.1815. Gram-scale synthesis

• , 124.8, 125.2, 126.8, 129.0, 129.05, 129.13, 129.9, 131.0, 133.8, 134.5, 138.8, 142.6; IR (neat) ν: 3053, 2966, 2883, 1489, 1396, 1132, 1043, 984, 831, 756 cm–1; HRMS (APCI+) m/z: [M + H]+ calcd. for C30H29O4, 453.2060; found, 453.2081. Gram-scale synthesis: Compound 4b was also prepared by the method

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

• equiv) resins packed into an Omnifit glass column (10 cm length, 10 mm i.d., rt). This approach facilitated the removal of triethylamine, residual acid substrate, and diphenylphosphonic acid (generated from DPPA) and rendered a solution of the carbamate product containing only unreacted benzyl alcohol

• ) via a T-piece with the flow stream exiting the scavenger column (A15/A21). The combined stream was then directed into an Omnifit column (10 cm length, 6.6 mm i.d.) containing immobilized CALB (tRes ca. 2–5 min; rt). The flow set-up for the CALB-mediated impurity tagging approach is depicted in Scheme

• solid K2CO3 packed into an Omnifit glass column (10 cm length, 10 mm i.d., filled with powdered K2CO3) was trialed as a heterogeneous reagent. A simple flow process was quickly realized in which a solution of the carbamate substrate (0.5 M toluene, 1.0 equiv) containing either acrylonitrile or methyl

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

• downfield shift of the 19F NMR chemical shift of the CF3 group but also by a CO shift to a higher frequency. As a general example, 111a (δ19F = −75.9 ppm; νCO = 2051, 2001, 1984, and 1942 cm−1) affords 113a (δ19F = −59.2 ppm; νCO = 2104, 2065, 2055, 2006, and 1989 cm−1), which exhibits the previously

• mentioned features, with Δδ19F = +16.7 ppm and ΔνCO ≈ +50 cm−1. Beyond the synthetic challenges associated with the generation of such species, the authors explored their use in organic synthesis. These metal-stabilized α-(trifluoromethyl)propargylium ions 114 could be engaged in useful transformations