Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO₂ fixation by N-benzyl cyclic guanidine under dry and wet conditions

• Yoshiaki Yoshida,
• Naoto Aoyagi and
• Takeshi Endo

Beilstein J. Org. Chem. 2018, 14, 2204–2211, doi:10.3762/bjoc.14.194

• ). Characterization of zwitterion adduct 2 and bicarbonate salt 3 by FTIR-ATR and solid-state 13C-CPMAS NMR IR spectra of 2 and 3 were measured by FTIR-ATR methods (Figure 3). The two peaks were clearly observed at 1573 cm−1 and 1706 cm−1 due to carbonyl and imine moieties, respectively, in the spectrum of 2. On the

• revealed by 13C-CPMAS NMR in solid-state (Figure 4). The carbon peaks due to the trapped CO2 and guanidinium moieties were observed at 135.4 ppm and 157.2 ppm, respectively, in the spectrum of 2, which indicated the zwitterionic structure between CO2 and 1. On the other hand, the carbon peaks due to the

• give zwitterion adduct 2 as a white powder. Zwitterion adduct 2: Yield 798 mg, 91%; mp 92.1–109.4 °C; IR (ATR, cm−1) 1706 (C=N), 1573 (C=O); 13C-CPMAS NMR (99.5 MHz, 25 °C) δ (ppm) 157.2 (C=N), 137.3 (aromatic), 135.4 (CO2), 129.5 (aromatic), 48.6 and 47.1 (NCH2CH2NH), 42.6 (CH2Ph); anal. calcd for

Cross-linked cyclodextrin-based material for treatment of metals and organic substances present in industrial discharge waters

• Élise Euvrard,
• Nadia Morin-Crini,
• Coline Druart,
• Justine Bugnet,
• Bernard Martel,
• Cesare Cosentino,
• Virginie Moutarlier and
• Grégorio Crini

Beilstein J. Org. Chem. 2016, 12, 1826–1838, doi:10.3762/bjoc.12.172

• magic angle spinning (CPMAS) spectrum shows the peaks of disordered cyclodextrin (broad signals) in the range of 50–110 ppm. Three strong broad bands attributable to the glucopyranose unit can be observed. The peak at 101 ppm is attributed to the anomeric carbon C-1: this confirms the presence of

• ester crosslinks, respectively. In the CPMAS spectrum we also note the presence of additional peaks due to the hydroxypropyl group present in the CD, and in particular the CH3 group (C-9 carbon) at 15.3 ppm. The comparison between the CPMAS and MAS spectra shows a different intensity for this methyl

• polymers: non-activated and activated polyBTCA-CD. CPMAS and MAS spectra of polyBTCA-CD. Adsorption capacity (%) of (a) the non-activated and (b) the activated (NaHCO3 treatment) polyBTCA-CD at different concentrations for five metals (at 10 mg·L−1 metal). Adsorption kinetics for two solutions containing

An experimental and theoretical NMR study of NH-benzimidazoles in solution and in the solid state: proton transfer and tautomerism

• Carla I. Nieto,
• Pilar Cabildo,
• M. Ángeles García,
• Rosa M. Claramunt,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2014, 10, 1620–1629, doi:10.3762/bjoc.10.168

• .10.168 Abstract This paper reports the 1H, 13C and 15N NMR experimental study of five benzimidazoles in solution and in the solid state (13C and 15N CPMAS NMR) as well as the theoretically calculated (GIAO/DFT) chemical shifts. We have assigned unambiguously the "tautomeric positions" (C3a/C7a, C4/C7 and

• C5/C6) of NH-benzimidazoles that, in some solvents and in the solid state, appear different (blocked tautomerism). In the case of 1H-benzimidazole itself we have measured the prototropic rate in HMPA-d18. Keywords: CPMAS; DNMR; GIAO; proton transfer; tautomerism; Introduction Of almost any class of

• carbon atom of the CF3 substituent (halogen substituents produce effects that are not well reproduced by our calculations that not include relativistic corrections) [15], removing it does not significantly modify the regression values (compare eqs. 3–6 with eqs. 7–10). CPMAS values agree better with

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

• Marta Pérez-Torralba,
• Rosa M. Claramunt,
• M. Ángeles García,
• Concepción López,
• M. Carmen Torralba,
• M. Rosario Torres,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2013, 9, 2156–2167, doi:10.3762/bjoc.9.253

• + (2.7 ± 0.7) CPMAS. The worse points are 1 DMSO-d6, F9 exp. −151.1, fitted −155.8; 2 toluene-d8, F9 exp. −146.3, fitted −142.9. The reason of this anomaly concerning the fluorine atoms closer to the nitrogen atoms remains unclear. In what concerns the FF coupling constants, 3JFF and 5JFF agree with the

• chemical shifts at 168.7 ppm for 1 and 170.9 for 2, in accordance with the calculated values. However, the 13C CPMAS signals corresponding to carbon atoms C6 to C9 could not be properly analyzed, and only the centers of the multiplets are given (138.1 and 138.6 ppm for 1 and 2, respectively). Some

• , driving and cooling gas. Solid state 13C (100.73 MHz) and 15N (40.60 MHz) CPMAS NMR spectra have been obtained on a Bruker WB 400 spectrometer at 300 K using a 4 mm DVT probehead. Samples were carefully packed in 4 mm diameter cylindrical zirconia rotors with Kel-F end-caps. Operating conditions involved

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225