Cascade trifluoromethylthiolation and cyclization of N-[(3-aryl)propioloyl]indoles

• Ming-Xi Bi,
• Shuai Liu,
• Yangen Huang,
• Xiu-Hua Xu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2020, 16, 657–662, doi:10.3762/bjoc.16.62

• ), which suggested that the radical process was probably involved in these transformations. Notably, no TEMPO-trapped product was detected by 19F NMR spectra of the crude reaction mixtures. On the basis of these results and literature studies [21][23][42][43][44][45][46][47], a plausible reaction mechanism

Asymmetric synthesis of CF₂-functionalized aziridines by combined strong Brønsted acid catalysis

• Xing-Fa Tan,
• Fa-Guang Zhang and
• Jun-An Ma

Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60

• ) were added and the mixture was reacted at rt for 24 hours unless otherwise annotated. The yields are those of isolated products, and the dr was determined by 19F NMR analysis of the crude mixture. The results in parentheses are those of isolated products after the dissolution–filtration process: The

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• of TIPS-ethynyl-substituted BODIPY derivatives 3–6 were characterized by 1H and 19F NMR spectroscopy, high-resolution mass spectrometry, and X-ray crystallographic analysis. The solid-state structures of the diethynyl-substituted BODIPYs were unambiguously elucidated by X-ray diffraction analysis (3a

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

• Svetlana V. Amosova,
• Andrey A. Filippov,
• Nataliya A. Makhaeva,
• Alexander I. Albanov and
• Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

• and 8 were proved by 1H, 13C, 15N, 19F and 77Se NMR and mass spectrometry. The composition of the products was confirmed by elemental analysis. Molecular ions of the synthesized compounds were observed in their mass spectra. Two doublets of the olefinic protons of the SCH=CHSe group with 3J = 6.3–6.6

• Information Supporting Information File 234: Experimental section and 1H, 13C, 15N, 19F and 77Se NMR spectra of all synthesized compounds. Acknowledgements The authors thank Baikal Analytical Center SB RAS for providing the instrumental equipment for structural investigations.

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• (Triaz)), 28.8 (s, 2 CHCH3 (Triaz)), 124.4 (s, CArH), 124.5 (s, CArH), 131.0 (s, CArH), 134.2 (s, CArH), 140.8 (s, CIV), 145.8 (s, CH (IPr)), 148.9 (s, CIV), 177.5 (s, Ccarbene); 19F{1H} NMR (282 MHz, CDCl3, 298 K) δ (ppm) −78.6 (s); anal. calcd for C33H41CuF3N3O3S: C, 58.26; H, 6.07; N, 6.18; found: C

• (IPr)), 31.3 (s, CCH3), 35.0 (s, CIV), 37.6 (s, CH3), 123.4 (s, CIV), 123.9 (s, CArH), 124.2 (s, C4 and C5), 124.4 (s, CArH), 126.6 (s, CArH), 129.4 (s, CArH), 130.5 (s, CArH), 130.9 (s, CArH), 134.3 (s, CIV), 144.8 (s, CIV), 145.2 (s, CIV), 152.0 (s, CIV), 152.8 (s, CIV), 179.4 (s, Ccarbene); 19F{1H

• (s, CHCH3 (Triaz)), 31.3 (s, CCH3), 35.0 (s, CIV), 37.8 (s, CH3), 123.6 (s, CIV), 124 (s, CArH), 126.2 (s, CArH), 129.0 (s, CArH), 131.1 (s, CArH), 134.3 (s, CIV), 145.0 (s, CIV), 149.2 (s, CIV), 153.4 (s, CIV); 19F{1H} NMR (282 MHz, CDCl3, 298 K) δ (ppm) −154.9 (s, BF4), −155.0 (s, BF4); anal. calcd

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• ), 19F NMR (376 MHz, CDCl3) δ 69.06; HRMS–APCI (m/z): [M + H]+ calcd for C38H35F2N2O2, 589.2644; found, 589.2661. The enantiomeric purity was confirmed by HPLC analysis: CHIRAL ART Cellulose-SB column, n-hexane/chloroform 95:5, 1.0 mL/min, 40 °C; (S)-2: tR = 9.86 min, (R)-2: tR = 21.29 min, UV detection

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

• MHz), 19F NMR (376 MHz), and 13C{1H} NMR (100 MHz) spectra were measured on a JEOL ECZ400 spectrometer as a CDCl3 solution, unless otherwise noted. The chemical shifts were expressed in ppm with CHCl3 (7.26 ppm for 1H), C6F6 (−164.9 ppm for 19F), or CDCl3 (77.16 ppm for 13C) as internal standards. IR

• Hz, 2H), 6.79 (s, 1H), 6.91 (d, J = 5.0 Hz, 1H), 7.17 (d, J = 5.0 Hz, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 0.4, 2.1, 18.3, 20.5 (br), 23.4, 27.4, 29.0, 30.4 (t, J = 22 Hz), 34.5, 124.3, 125.1, 126.0, 129.7, 130.2, 133.6, 137.6, 140.3; 19F NMR (376 MHz, C6F6) δ −129.2, −127.6, −117.6, −84.2; IR (ATR

• , 1H); 13C{1H} NMR (100 MHz, CDCl3) δ −0.2, 2.0, 17.6, 20.5 (br), 23.1, 27.4, 29.0, 30.4 (t, J = 22 Hz), 34.3, 124.3, 125.1, 126.0, 129.7, 130.2, 133.6, 137.6, 140.2; 19F NMR (376 MHz, C6F6) δ −129.2, −127.6, −117.6, −84.2; IR (ATR): 2958, 1252, 1233, 1167, 1134, 1046, 870, 841, 800, 783, 754, 719, 689

Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C–F···H–C bonds

• Vuyisa Mzozoyana,
• Fanie R. van Heerden and
• Craig Grimmer

Beilstein J. Org. Chem. 2020, 16, 190–199, doi:10.3762/bjoc.16.22

• conditions via a three-step reaction. The solution-state 1H NMR spectra of 6 showed a strong intramolecular interaction between F and H5 (JFH = 2.6 Hz) and 13C NMR suggested that this C–F···H–C coupling is a through-space interaction. The 2D 19F-{1H} HOESY and 1H-{19F} 1D experiments were done to confirm

• ). The H5 signal was expected to be a doublet (not a dd) due to 3J coupling to H6, since an H,H-COSY experiment does not show coupling between H5 and H8 (Figure S9, Supporting Information File 1). It became clear that the splitting of the signal from H5 was due to coupling with the 19F atom by comparing

• the spectra from the 1H and 1H-{19F} experiments (Figure 1) which showed the H5 peak as a doublet with 19F decoupling. While the doublet-of-doublets signal for H5 collapses into a doublet with 19F decoupling, there are no significant changes in the line-shape for the signal of H3 with 19F decoupling

Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

• Jucleiton J. R. Freitas,
• Queila P. S. B. Freitas,
• Silvia R. C. P. Andrade,
• Juliano C. R. Freitas,
• Roberta A. Oliveira and
• Paulo H. Menezes

Beilstein J. Org. Chem. 2020, 16, 168–174, doi:10.3762/bjoc.16.19

• propargylating agent in a very regioselective way [36][37]. Thus, allenylboronic acid pinacol ester (1) was converted into the corresponding trifluoroborate using the procedure described by Lloyd-Jones and co-worker [38]. The desired product 4 was obtained in good yield and characterized by 1H, 13C, 11B and 19F

• solvents.a Supporting Information Supporting Information File 252: Experimental procedures and 1H, 13C, 11B and 19F NMR spectra for all synthesized compounds. Funding This work was jointly supported by grants from CNPq and FACEPE.

Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

• Valentina A. Ol’shevskaya,
• Elena G. Kononova and
• Andrei V. Zaitsev

Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263

• ) or Ni(II) with N-propargylmaleimide via the CuAAC click reaction to afford fluorinated porphyrin–triazole–maleimide conjugates. New maleimide derivatives were isolated in reasonable yields and identified by UV–vis, 1H NMR, 19F NMR spectroscopy and mass-spectrometry. Keywords: chlorin; maleimide

• was transformed into the corresponding maleimide 12 in 25% yield on the reaction with maleic anhydride according to the standard procedure. Chlorin 12 was metalated with Zn(OAc)2/CHCl3/MeOH giving chlorin 13 in 92% yield. (Scheme 2). All prepared compounds have been structurally identified by 1H, 19F

Synthesis of aryl-substituted thieno[3,2-b]thiophene derivatives and their use for N,S-heterotetracene construction

• Nadezhda S. Demina,
• Nikita A. Kazin,
• Nikolay A. Rasputin,
• Roman A. Irgashev and
• Gennady L. Rusinov

Beilstein J. Org. Chem. 2019, 15, 2678–2683, doi:10.3762/bjoc.15.261

• Crystallographic Data Centre via https://www.ccdc.cam.ac.uk/data_request/cif. Supporting Information File 569: Experimental section and copies of 1H, 13C and 19F NMR spectra of new compounds. Supporting Information File 570: Crystal data of 7d. Acknowledgements This study was supported by the Russian Foundation

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• triphenylphosphane and N-triflyl-propiolanilide 1a in dichloromethane yielded a product mixture, from which only N-phenyltriflylamide (HN(Ph)Tf; 19F NMR: δ −76.5 ppm rel. to C6F6) could be extracted, the remainder being undefined oligomeric/polymeric material. However, when an N-triflylpropiolamide 1a–e (1.03 molar

• Information Supporting Information File 640: Experimental procedures, characterization data, NMR spectra (1H, 13C, 31P, 19F) and IR spectra for the synthesized compounds, and data for the X-ray crystal structure determinations.

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• DAE 4 could not be isolated by column chromatography on regular silica gel. Instead, monoiodide 4 was obtained in 14% yield as colorless solid after preparative HPLC on a reversed phase (C18) column and lyophilization. The constitution and structure of 4 was confirmed by HRMS, 1H and 19F NMR

• closed form (formed by handling in the lab not fully protected from light) were detected by HPLC (Figure S33 in Supporting Information File 1). The constitution, structures, and purities of the final products were confirmed by HRMS, 1H and 19F NMR spectroscopy, as well as analytical HPLC. Saponification

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• were used without further purification. Melting points were determined on a Yanaco MP-500D melting point apparatus and are uncorrected. 1H (400 MHz), 13C (100 MHz) and 19F NMR (376 MHz) spectra were recorded on a JEOL JNM-400 spectrometer at ambient temperature. The splitting patterns are designated as

• , 123.9, 123.0, 122.5, 122.2, 121.7, 121.2, 119.4, 117.5, 113.2, 111.0, 55.5, 14.7, 14.77; 19F NMR (376 MHz, CDCl3, ppm) δ −113.1 (s, 2F), −113.3 (s, 2F), −135.0 (s, 2F); HRMS (MALDI–TOF) m/z: calcd for C35H24F6N2OS2, 666.1234; found, 666.1229. Diarylethene (1o) To 5 mL of dichloromethane anhydrous

• , 142.8, 142.6, 142.1, 141.4, 137.7, 133.4, 130.1, 129.2, 129.2, 128.2, 126.3, 125.9, 125.9, 125.8, 125.8, 124.6, 123.7, 122.5, 121.5, 120.7, 119.2, 117.9, 117.0, 116.1, 107.3, 14.7, 14.7; 19F NMR (376 MHz, CDCl3, ppm) δ −113.1 (s, 2F), −113.3 (s, 2F), −135.0 (s, 2F); HRMS (MALDI–TOF) m/z: calcd for

Friedel–Crafts approach to the one-pot synthesis of methoxy-substituted thioxanthylium salts

• Kenta Tanaka,
• Yuta Tanaka,
• Mami Kishimoto,
• Yujiro Hoshino and
• Kiyoshi Honda

Beilstein J. Org. Chem. 2019, 15, 2105–2112, doi:10.3762/bjoc.15.208

• ), coupling constants, integration. 13C NMR spectra were recorded on a Bruker DRX-500 (126 MHz) or a JEOL JNM ECA-500 (126 MHz) spectrometer with complete proton decoupling. Chemical shifts are reported in ppm with the solvent resonance as the internal standard (CDCl3: δ 77.0). 19F NMR spectra were recorded

• , 6H); 13C NMR (126 MHz, CDCl3) δ 168.3. 165.5. 165.2. 147.8. 142.2. 127.2. 127.0. 125.6. 116.9. 101.8. 101.4. 57.7. 56.7; 19F NMR (376 MHz, CDCl3) δ −81.3; IR (ATR): 1585, 1219, 1143, 1026, 634 cm−1; HRMS (ESI+) m/z: [M]+ calcd for C23H21O4S, 393.1155; found, 393.1171; anal. calcd for C24H21F3O7S2: C

• Hz, 1H), 6.93 (dd, J = 7.1, 1.1 Hz, 1H), 6.43 (d, J = 2.2 Hz, 2H), 4.15 (s, 6H), 2.96 (s, 6H); 13C NMR (126 MHz, CDCl3) δ 168.4, 165.2, 164.7, 147.6, 140.7, 132.1, 132.0, 128.2, 127.5, 126.4, 125.9, 125.0, 124.4, 121.3, 117.6, 102.0, 101.5, 57.7, 56.6; 19F NMR (376 MHz, CDCl3) δ −81.3; IR (ATR): 1593

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• , 146.58; 19F NMR (DMSO-d6) δ 148; HRMS (ESIMS) m/z: [M2+]; calcd. for C12H16N42+ 216.1364 108.0682; found, 108.0683. 1,4-Diacetyl)-1,2,3,4-tetrahydropyrazino[2,3-g]quinoxaline (9): 1,2,3,4-Tetrahydropyrazino[2,3-g]quinoxaline (3, 500 mg, 2.68 mmol) was added to 20 mL of acetic anhydride and the mixture

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• = 6.4 Hz, 6H); 19F NMR (376 MHz, DMSO-d6, 25 °C) δ 59.8; 13C NMR (101 MHz, MeCN-d3, 25 °C) δ 167.1, 164.5, 154.8, 145.0, 144.2, 131.2, 125.9, 124.7 (q,1J(C, F) = 271.6 Hz), 124.5, 120.9 (q, 2J(C, F) = 31.8 Hz), 117.1, 36.5, 35.5, 28.2; IR (KBr, cm−1) ν: 3372, 3080, 2937, 1775, 1717, 1603, 1545, 1382

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• . Stereochemistry of the alcohol 58 was established by long-range 19F coupling to the cis-trimethylsilyl group hydrogens (JH-F = 0.9 Hz). Long-range 19F coupling to the TMS methyl groups of 58 was also observed in the 13C NMR spectrum (JC-F = 2.1 Hz) [64][65]. This long-range 19F coupling is not observed when the

Fluorine-containing substituents: metabolism of the α,α-difluoroethyl thioether motif

• Andrea Rodil,
• Alexandra M. Z. Slawin,
• Nawaf Al-Maharik,
• Ren Tomita and
• David O’Hagan

Beilstein J. Org. Chem. 2019, 15, 1441–1447, doi:10.3762/bjoc.15.144

• 19F NMR spectrum consistent with non-equivalence of the fluorines, immediately indicative of sulfoxide formation. Isolation and subsequent 1H and 19F NMR analyses as well as high-resolution mass spectrometry secured the identity of these metabolites as sulfoxides 6 and 7 and sulfone 8. The structure

• naphthalene ring, as summarised in Scheme 3. These metabolites were isolated by reversed-phase HPLC and characterised by 1H and 19F NMR and mass spectrometry. This identified sulfoxides 11 and 12 as the major metabolites and a trace amount of a minor sulfone which had the general structure 13 as determined by

• hydrolytic lability of the analogous oxygen ethers. By way of example α,α-difluoroethyl ether 14 [18] was incubated with cultures of C. elegans under the standardised conditions, as illustrated in Scheme 4. 19F NMR of the extract indicated a trace of residual starting material with one major metabolite which

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• stated in the procedure. NMR spectra were collected on a Bruker Ultrashield Plus/Avance II 400 MHz spectrometer. 1H NMR spectra were recorded at 400 MHz and 13C NMR spectra at 100 MHz with residual solvent signals as references. 19F NMR spectra were recorded at 376 MHz. Stereochemistry was assigned

• = 11.4 Hz, 7.2 Hz, 1H, H7), 3.69 (dd, J = 11.5 Hz, 4.6 Hz, 1H, H7), 3.60–3.49 (m, 4H); 13C NMR (100 MHz, CD3OD) δ 161.6, 146.2, 127.4, 127.3, 126.6, 122.4, 115.5, 115.3, 79.0, 78.6, 74.7, 69.4, 68.4, 61.5, 51.6; 19F NMR (376 MHz, CD3OD) δ −115.54; HRMS (m/z): [M + H]+ calcd for 340.1306; found, 340.1309

• ), 3.90 (dd, J = 2.9 Hz, 0.9 Hz, 1H, H5), 3.79 (dd, J = 11.2 Hz, 6.9 Hz, 1H, H7), 3.70 (dd, J = 11.6 Hz, 4.71 Hz, 1H, H7), 3.60–3.48 (m, 4H); 13C NMR (100 MHz, CD3OD) δ 164.5, 146.2, 132.9, 130.5, 122.9, 121.1, 114.4, 111.9, 78.9, 78.7, 74.7 69.4, 68.4, 61.5, 51.5; 19F NMR (376 MHz, CD3OD) δ −114.83; HRMS

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• nature of the halogen bond assembly. The crystal lattice of 1 contains two structurally different dimeric assemblies A and B, formally resulting in the mixture of a capsular dimer and a dimeric pseudo-capsule. 1H and 19F NMR analyses supports the existence of these halogen-bonded complexes and enhanced

• –NH2 protons of the NARXs are expected [32][33]. Additionally, NARXs are also known to cooperatively bind small guest molecules such as mono- and diamides [42][43]. Consequently, we used 1H and 19F NMR spectroscopy to study the XB assemblies formed between Hex-NARBr 1 and 1,4-diiodooctafluorobutane (5

• acetonitrile. The 1H and 19F NMR spectra of all these samples were recorded at 298 K and analyzed. In the 19F NMR analyses, the fluorine signals of the XB donor DIOFB were monitored. In all cases, minor upfield shifts of the fluorines on the terminal carbons were observed (0.12 ppm in 1·DIOFB, 0.13 ppm in 1

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

• Laize A. F. Andrade,
• Lucas A. Zeoly,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2019, 15, 506–512, doi:10.3762/bjoc.15.44

• interactions (nN → σ*C–F), which can be demonstrated by means of 19F chemical shifts. The results were rationalized with the aid of theoretical calculations and natural bond orbital (NBO) analysis, allowing for the evaluation of competing steric, electrostatic and hyperconjugative interactions. Keywords

• enhance the fluoride character of the fluorine involved in such interaction. Because of the negative charge on the fluorine in the resonance structure derived from the generalized anomeric effect, a shielding effect is expected for this fluorine. The 19F NMR assignment of the diastereotopic fluorines was

• possible considering the 3JH,F(1) SSCC earlier reported, and comparing the 19F and 19F{1H} NMR experiments: the more shielded diastereotopic fluorine corresponds to Fpro-S, thus yielding 1b as the dominant conformation. Such a shielding effect decreases on going from cyclohexane (−89.4 ppm) to pyridine

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• achieved in the presence of Pd/C as a catalyst. Concomitant hydrogenolysis of two carbon–chlorine bonds also took place under these conditions and a 71:29 diastereomeric mixture of the monochloracetamides 19f/19’f was obtained (41%). The rather small difference of steric hindrance between the methyl and

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• leads to the selective formation of the desired 1,2-trans glycosidic linkages and can be easily removed at the end of the synthesis [7][8][36][42]. Moreover, 19F NMR experiments can be employed to assist in the analysis and monitoring of reactions involving N-TFA building blocks. First, we describe the

• -2C (δ = 4.50 ppm in 14α; δ = 3.52–3.43 ppm in 14β). The value of the coupling constant J1,2 in ring C confirmed the configuration of the new glycosidic linkage (J1,2 = 3.2 Hz in 14α; J1,2 = 8.2–8.5 Hz in 14β). 19F NMR spectra also showed clear differences in the chemical shifts for the

A convenient and practical synthesis of β-diketones bearing linear perfluorinated alkyl groups and a 2-thienyl moiety

• Ilya V. Taydakov,
• Yuliya M. Kreshchenova and
• Ekaterina P. Dolotova

Beilstein J. Org. Chem. 2018, 14, 3106–3111, doi:10.3762/bjoc.14.290

• compounds 3a–g and 5. Supporting Information File 522: Copies of 19F and 13C NMR spectra and LR mass spectra of compounds 3a–g and 5. Acknowledgements We are grateful to the Russian Science Foundation (grant No. 19-13-00272) for supporting the synthetic part of this work. Financial support for the NMR and