Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

• Josué M. Silla,
• Claudimar J. Duarte,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2014, 10, 877–882, doi:10.3762/bjoc.10.84

• a 2-substituted ethylamine fragment [1][2][3][4][5]. According to theoretical calculations, such conformational preference takes place in the gas phase and persists in water solution, where most biochemical processes occur. We have recently shown that, in water solution, the axial preference of 3

• and Discussion The conformational isomerism of 2,2-difluoroethylamine (1) was computationally investigated at the MP2/6-311++g(d,p) level, both in the gas phase and implicit water (using the Polarizable Continuum Model). The conformational preferences are consistent with those obtained elsewhere

• perturbation analysis of donor-acceptor interactions in the natural bond orbitals (NBOs) framework shows that the global minimum of 1 is more stabilized by hyperconjugation than the other conformers (both in the gas phase and implicit water), despite being significantly destabilized by Lewis-type interactions

Chromatographically separable rotamers of an unhindered amide

• Mario Geffe,
• Lars Andernach,
• Oliver Trapp and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63

• - and Z-isomer of 4 is predicted to be 3.2 kJ/mol in hexane and 5.8 kJ/mol in vacuo, respectively. The transition states are located at 108.8 kJ/mol (TS1) and 105.5 kJ/mol (TS2) above the Z-isomer of 4 for hexane solvation as well as at 107.3 k/mol (TS1) and 102.1 kJ/mol (TS2) in the gas phase

• −284.0 cm−1 (TS1) and −362.2 cm−1 (TS2) in the gas phase). This imaginary frequency belongs to the rotational vibration of the formyl hydrogen and the formyl oxygen along the reaction pathway for the E/Z isomerization of 4. In both transition states geometries, the C–N bond (143 pm) is significantly

• , quant. Relative Gibbs free energy (kJ/mol) for E-4, Z-4, TS1, TS2, GSDMF, TS1DMF and TS2DMF in the gas phase and with COSMO solvation for hexane, ethanol and DMSO at 298 K (BP-D3/def2-SVP). Supporting Information Supporting Information File 168: Experimental procedures, HPLC chromatograms, copies of 1D

Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

• nitration of thioureas is based on subsequent nitrosation and nitration steps. The same group also analyzed continuous processes to perform the strongly exothermic nitration of naphthalene (47) (Scheme 14) with N2O5, both in the gas phase and in the liquid phase [49][50]. The authors reported that the

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 259–270, doi:10.3762/bjoc.10.21

• at the reaction center was prepared by the use of Z matrices. For instance, in the gas phase SN2 reaction Cl− + H3C–Br → Cl–CH3 + Br−, Cl···C and C···Br intermediate distances were assumed. The geometry was optimized under the constraint of the fixed Cl–C and C–Br distances. After the partial

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• of quantum chemical programs. Geometry optimizations of intermediates, transition states, reactants, and products in the gas phase were performed at the PBE1PBE/6-31G(d) level by using Gaussian 09 [38]. Stationary points on the respective potential energy surfaces were characterized at the same level

One-pot sequential synthesis of isocyanates and urea derivatives via a microwave-assisted Staudinger–aza-Wittig reaction

• Diego Carnaroglio,
• Katia Martina,
• Giovanni Palmisano,
• Andrea Penoni,
• Claudia Domini and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2013, 9, 2378–2386, doi:10.3762/bjoc.9.274

• established as a reliable technique which can be applied on a range of scales [26]. Despite MW irradiation being commonly used in organic synthesis, only few publications describe this technique with gaseous reagents in closed vessels and in heterogeneous gas-phase reactions that are important for industrial

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• pyridine structural class. Pyridine itself is produced industrially by either the traditional Chichibabin pyridine synthesis (Scheme 1, A), the Bönnemann reaction, a cobalt-catalysed cyclotrimerisation of alkynes and nitriles (Scheme 1, B) or the aerobic gas-phase condensation of croton aldehyde

• flow process at their main plant in Visp, Switzerland. An alternative process is based on the availability of 3-picoline (1.15) which is generated as a major side product in the synthesis of pyridine prepared from formaldehyde, acetaldehyde and ammonia in a gas phase reaction (Scheme 3) [25]. The 3

• -picoline can be readily oxidised via another gas-phase protocol using a fixed-bed reactor charged with vanadium pentoxide on high surface titanium dioxide (5–50 wt % vanadium). A modification of the sequence utilises a dehydrative amminolysis (ammoxidation) to furnish the corresponding 3-cyanopyridine

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• phase results do not differ significantly neither in terms of geometry nor energy, we will restrict the discussion to gas phase values only unless otherwise stated (for details of the PCM results see Supporting Information File 1). The CBS-QB3 method has been used to obtain accurate energies and to

• enone 24. Only one enantiomer of racemic compounds is shown. Model substrates 11A and 11B that allowed a determination of accurate BDH298 values with the CBS-QB3 method. Optimized geometries and BDH298 values of radicals derived from 11 and 12 for gas phase and PCM calculations. Supporting Information

• Supporting Information File 1) of relative radical stabilities and bond-dissociation enthalpies (BDH298) based on DFT (B3LYP/6-31+G** and B3LYP/6-31G* + PCM) and composite method (CBS-QB3) calculations enable a quantification and visual rationalization of the observed experimental results. Since PCM and gas

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

• solvates as well as dimeric forms [14] (they do not consider tautomer 3e). In the gas phase their relative energies (in kJ mol−1) are: 3a (0.0) > 3b (14.6) > 3d (48.5) > 3c (93.4) and with an ethanol molecule they are: 3a (0.0) > 3b (0.6) > 3d (51.3) > 3c (70.0). The great stabilization of 3b due to

• ethanol does not correspond to that observed by Mannschreck in CDCl3 [11]. Our calculations (gas phase) are reported in Table 1. Our results agree with those of Okovytyy et al. [14] now including 3e: 3a (0.0) > 3b (14.7) > 3d (48.6) > 3e (64.0) > 3c (96.5). For the remaining compounds always is a (0.0

Damage of polyesters by the atmospheric free radical oxidant NO₃^•: a product study involving model systems

• Catrin Goeschen and
• Uta Wille

Beilstein J. Org. Chem. 2013, 9, 1907–1916, doi:10.3762/bjoc.9.225

• the reaction outcome and mechanic considerations, were avoided. It should also be noted that NO2• is in equilibrium with its dimer dinitrogen tetroxide, N2O4. In solution the NO2•/N2O4 equilibrium constant favours the dimer [15], and N2O4 can be oxidized with O3 to give N2O5. Gas-phase kinetic studies

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• aqueous solution of the inclusion complex of ACE with γ-CD thioether. Molecular modeling: A previously described procedure was used [25]. The geometries of the orientational isomers of the COU gas-phase dimer were fully optimized without any symmetry restriction at the MP2/6-31G* level of theory by using

Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

• Andreas Gansäuer,
• Meriam Seddiqzai,
• Tobias Dahmen,
• Rebecca Sure and
• Stefan Grimme

Beilstein J. Org. Chem. 2013, 9, 1620–1629, doi:10.3762/bjoc.9.185

• protocol consists of gas phase structure optimization at the dispersion-corrected DFT-D3 level using large triple-zeta AO basis sets (TPSS-D3/def2-TZVP) followed by accurate single-point energy calculations at the meta-hybrid level with a further extended AO basis set (PW6B95-D3/def2-QZVP), thermo

• harmonic vibrational frequencies were performed analytically using the TURBOMOLE module aoforce. Thermal corrections from energy to free enthalpy were calculated within the standard harmonic-oscillator approximation for each molecule in the gas phase. The vibrational frequencies were used unscaled. The

• optimized gas phase geometries. The solvation contribution was then added to the gas phase free energies. The 5-exo cyclization as benchmark In order to find reliable computational methods for the description of the radical additions, we sought for systems for benchmarking that are structurally related to

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• alleviate the unsaturation makes them very reactive species but hampers their isolation. Low-coordinate Pt(II) complexes have been generated in gas-phase experiments [6][7] but have remained elusive in solution. With a few exceptions the fourth coordination site is occupied by a weak ligand, e.g., an

• calculations correctly explain the relative stabilities of 51 with respect to 37a depending on the polarity of the solvent [127]. This kind of reactivity has also attracted attention in gas-phase conditions [122]. The gas-phase behavior of cationic species 52 has been analyzed by means of combined experimental

A study on electrospray mass spectrometry of fullerenol C₆₀(OH)₂₄

• Mihaela Silion,
• Andrei Dascalu,
• Mariana Pinteala,
• Bogdan C. Simionescu and
• Cezar Ungurenasu

Beilstein J. Org. Chem. 2013, 9, 1285–1295, doi:10.3762/bjoc.9.145

• fullerenide-fullerenate anions, and ions M5 and M7 shall be named fullerenoxyl-fullerenate and fullerenyl-fullerenate distonic anions, respectively. To avoid any confusion with dissociative electron attachment (DEA) (addition of a free electron to a gas-phase molecule to give an anion and a neutral molecule

• undergo an unanticipated gas-phase rearrangement that involves the partial (in the negative mode from pure aqueous media) or total (in the positive mode and negative mode from ammonia aqueous solutions) π-bond reconstruction of the C60 cage by rehybridization and redistribution of odd electrons of

Linkage of α-cyclodextrin-terminated poly(dimethylsiloxanes) by inclusion of quasi bifunctional ferrocene

• Helmut Ritter,
• Berit Knudsen and
• Valerij Durnev

Beilstein J. Org. Chem. 2013, 9, 1278–1284, doi:10.3762/bjoc.9.144

• by circular dichroism spectroscopy [8] and thermogravimetric analysis [9]. In addition, the complex of ferrocene and α-CD could be detected in the gas phase by mass spectrometry [10]. Recently, there have been many reports focusing on the use of α-CD in aqueous solution as a mobile phase for optical

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• photoinduced addition of tetrafluorodiphosphine to alkenes and alkynes in the gas phase (Table 3) [31][32][33][34]. The addition provides a series of intriguing bidentate phosphine ligands. The addition to alkynes yields 1:1 mixtures of E/Z isomers. Due to the high reactivity of a difluorophosphanyl radical

Host–guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V

• Svetlana Begel,
• Ralph Puchta and
• Rudi van Eldik

Beilstein J. Org. Chem. 2013, 9, 1252–1268, doi:10.3762/bjoc.9.142

• lithium [66] and beryllium [67] cations the preferable four-fold coordinated structures were found. They show additional water molecules, which do not interact directly with the metal center, but are held in the second coordination sphere by hydrogen bonds. However, the gas phase [Li(H2O)6]+ and [Be(H2O)6

• ]2+ and result in a distorted tetrahedron. Therefore, [Be 2.2.bpy]2+ and [Be 2.bpy.bpy]2+ can be considered as structures allowing appropriate coordination and stabilization in the gas phase, but in solution these structures will surely not be superior to solvated Be2+ and an empty cryptand. In

Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: synthesis and physical properties

• Neil Thomson,
• Alexander L. Kanibolotsky,
• Joseph Cameron,
• Tell Tuttle,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2013, 9, 1243–1251, doi:10.3762/bjoc.9.141

• properties between the two isomers, DFT calculations were performed on the smaller truxenes. The T1-3FTh and T1-4FTh structures were optimised in the gas phase by using the BP86-D [18][19][20] functional with the def2-TZVP [21] basis set implemented in TURBOMOLE 6.3.1 [22]. The optimisations were carried out

Space filling of β-cyclodextrin and β-cyclodextrin derivatives by volatile hydrophobic guests

• Sophie Fourmentin,
• Anca Ciobanu,
• David Landy and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1185–1191, doi:10.3762/bjoc.9.133

• gas phase were determined by HS-GC. Because of the high separation efficiency of the GC column, all five guests could be determined simultaneously (Figure 3). Since interference of binding of the various guests was negligible because of the very large excess of β-CDs compared to the guests, binding

Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

• Rahat Javaid,
• Shin-ichiro Kawasaki,
• Akira Suzuki and
• Toshishige M. Suzuki

Beilstein J. Org. Chem. 2013, 9, 1156–1163, doi:10.3762/bjoc.9.129

• residence time in the porous PdO reactor at 40 °C. Evolution of carbon dioxide (CO2) was observed during the reaction, although hydrogen (H2) was not found in the gas phase. Dehydrogenation of formic acid did not occur to any practical degree in the absence of p-nitrophenol. Consequently, the nitro group

• the pressure drop and plugging. The evolution of gas bubbles was observed during the reaction forming an alternate gas–liquid slug flow. GC analysis of the gas phase evidenced the evolution of CO2 as a sole product and H2 was not found. The hydrogenation reaction of p-nitrophenol was followed by UV

• reduction of nitro group is a possible reaction pathway. However as mentioned, CO2 was a sole product in the gas phase and H2 was not found even at an increased temperature of 70 °C. To ensure that the nitro group is not reduced by H2 generated by dehydrogenation of formic acid, we conducted a control test

Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

• Josué M. Silla,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2013, 9, 1127–1134, doi:10.3762/bjoc.9.125

• -Fluorophenylboronic acid undergoes rotational isomerization around the C–B and B–O bonds, giving rise to three energy minima (Figure 2), either in the gas phase or implicit CH3CN. Since the energy differences obtained by DFT were similar to those obtained by MP2, the B3LYP/aug-cc-pVDZ level was used for further

• ). According to NBO analysis, such an interaction is 3.4 and 3.9 kcal mol−1 stabilizing for 1a and 1b, respectively, but 1a is largely dominant both in the gas phase and in solution (Table 1). This is corroborated by the AIM results, whose molecular graphs indicate bond paths between F and H(O) for 1a and 1b

• (1a–2c) and B3LYP/aug-cc-pVDZ levels, followed by inspection of the harmonic frequencies, by using the Gaussian 09 program [26]. For 1a–2c, the calculations were carried out both for the gas phase and implicit CH3CN solvent, by using the polarizable continuum model by Tomasi and co-workers (in its

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

• Amaresh Mishra,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2013, 9, 866–876, doi:10.3762/bjoc.9.100

• platinum wire, and the reference electrode was an Ag/AgCl secondary electrode. All potentials were internally referenced to the ferrocene/ferricenium couple. Calculations. Full geometry optimizations were performed in the gas phase by using density functional theory (DFT) calculations based on the B3LYP

3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles

• Curt Wentrup,
• Nguyen Mong Lan,
• Adelheid Lukosch,
• Pawel Bednarek and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84

• strongly exothermic reactions. Consequently, when the reaction is performed in the low-pressure gas phase, the reaction products carry excess thermal (rovibrational) energy, which facilitates the sigmatropic shifts of H, CN, and CH3, which will cause interconversion of the cyanopyrroles [28]. In many cases

• –60% yield (Scheme 12). Importantly, smaller amounts of amine 51 and the ring-contraction product 2-phenyl-3-cyanoindole (48, 21–15%) were also isolated. Formation of amines is diagnostic for triplet nitrenes, even in low-pressure gas-phase reactions [10][22]. The 3-cyanoindole 48 is expected to be

Photoionisation of the tropyl radical

• Kathrin H. Fischer,
• Patrick Hemberger,
• Andras Bodi and
• Ingo Fischer

Beilstein J. Org. Chem. 2013, 9, 681–688, doi:10.3762/bjoc.9.77

• are reassigned to the C–C stretch mode ν16+ and to a combination of ν16+ with the ring breathing mode ν2+. Above 10.55 eV dissociative photoionisation of tropyl is observed, leading to the formation of C5H5+ and C2H2. Keywords: dissociative photoionisation; gas phase; reactive intermediates

• the radical was measured in the gas phase and compared to calculations as well as to that of the benzyl radical [15]. The geometry change upon ionisation and the character of the molecular orbitals triggered interest in the photoelectron spectroscopy of tropyl. The adiabatic ionisation energy of the

Complete σ* intramolecular aromatic hydroxylation mechanism through O₂ activation by a Schiff base macrocyclic dicopper(I) complex

• Albert Poater and
• Miquel Solà

Beilstein J. Org. Chem. 2013, 9, 585–593, doi:10.3762/bjoc.9.63

• states [65][66][67][68][69][70][71][72][73]. Solvent effects including contributions of non-electrostatic terms have been estimated in single-point calculations on the gas-phase-optimized structures, based on the polarizable continuous solvation model (PCM) with CH3CN as a solvent [74][75], i.e., the