@article{SzatmariBelasriHeydenreichetal.2019, author = {Szatmari, Istvan and Belasri, Khadija and Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Fulop, Ferenc}, title = {Ortho-Quinone methide driven synthesis of new O,N- or N,N-Heterocycles}, series = {ChemistryOpen : including thesis treasury}, volume = {8}, journal = {ChemistryOpen : including thesis treasury}, number = {7}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2191-1363}, doi = {10.1002/open.201900150}, pages = {961 -- 971}, year = {2019}, abstract = {To synthesize functionalized Mannich bases that can serve two different types of ortho-quinone methide (o-QM) intermediates, 2-naphthol and 6-hydroxyquinoline were reacted with salicylic aldehyde in the presence of morpholine. The Mannich bases that can form o-QM and aza-o-QM were also synthesized by mixing 2-naphthol, 2-nitrobenzaldehyde, and morpholine followed by reduction of the nitro group. The highly functionalized aminonaphthol derivatives were then tested in [4+2] cycloaddition with different cyclic imines. The reaction proved to be both regio- and diastereoselective. In all cases, only one reaction product was obtained. Detailed structural analyses of the new polyheterocycles as well as conformational studies including DFT modelling were performed. The relative stability of o-QMs/aza-o-QM were also calculated, and the regioselectivity of the reactions could be explained only when the cycloaddition started from aminodiol 4. It was summarized that starting from diaminonaphthol 25, the regioselectivity of the reaction is driven by the higher nucleophilicity of the amino group compared with the hydroxy group. 12H-benzo[a]xanthen-12-one (11), formed via o-QM formation, was isolated as a side product. The proton NMR spectrum of 11 proved to be very unique from NMR point of view. The reason for the extreme low-field position of proton H-1 could be accounted for by theoretical calculation of structure and spatial magnetic properties of the compound in combination of ring current effects of the aromatic moieties and steric compression within the heavily hindered H(1)-C(1)-C(12b)-C(12a)-C(12)=O structural fragment.}, language = {en} } @article{ShainyanSuslovaTranDinhPhienetal.2019, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Tran Dinh Phien, and Shlykov, Sergey A. and Heydenreich, Matthias and Kleinpeter, Erich}, title = {1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational preferences in gas and solution by GED, NMR and theoretical calculations}, series = {Tetrahedron}, volume = {75}, journal = {Tetrahedron}, number = {46}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2019.130677}, pages = {9}, year = {2019}, abstract = {1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature C-13 and Si-29 NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeSaxPheq conformer in gas phase (1-Ph-eq :1-Ph-ax = 55:45, Delta G degrees = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph-eq:1-Ph-ax = 65:35, Delta G degrees = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory. (C) 2019 Elsevier Ltd. All rights reserved.}, language = {en} } @article{ShainyanKleinpeterSuslova2019, author = {Shainyan, Bagrat A. and Kleinpeter, Erich and Suslova, E. N.}, title = {Conformational Analysis of (1,1′-Phenyl-1,1′-silacyclohex-1-yl)disiloxane}, series = {Russian journal of general chemistry}, volume = {89}, journal = {Russian journal of general chemistry}, number = {4}, publisher = {Pleiades Publ.}, address = {New York}, issn = {1070-3632}, doi = {10.1134/S1070363219040121}, pages = {713 -- 716}, year = {2019}, abstract = {The DFT and MP2 theoretical conformational analysis of the recently synthesized (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane has revealed the energetic preference of the Ph-ax,Ph-ax conformer. The Ph-ax,Ph-ax: Ph-ax,Ph-eq: Ph-eq,Ph-eq conformers ratio has been estimated as of 46.6: 33.1: 20.3 from the M062X/6-311G(d,p) free energy simulation, suggesting the possibility of detecting individual conformers experimentally, e.g., by low-temperature H-1 and C-13 NMR spectroscopy. However, only the presence of several conformers has been detected by means of H-1 NMR spectroscopy at 113 K; determination of the (Hz) and G(\#) (kcal/mol) parameters for the 6-membered ring interconversion has been impossible due to the signals broadening at low temperature, signal temperature shifts, and extremely low barrier of ring inversion at T-c < 113 K.}, language = {en} } @article{SardarianInalooModarresiAlametal.2019, author = {Sardarian, Ali Reza and Inaloo, Iman Dindarloo and Modarresi-Alam, Ali Reza and Kleinpeter, Erich and Schilde, Uwe}, title = {Metal-Free Regioselective Monocyanation of Hydroxy-, Alkoxy-, and Benzyloxyarenes by Potassium Thiocyanate and Silica Sulfuric Acid as a Cyanating Agent}, series = {The journal of organic chemistry}, volume = {84}, journal = {The journal of organic chemistry}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.8b02191}, pages = {1748 -- 1756}, year = {2019}, abstract = {A novel and efficient metal- and solvent-free regioselective para-C-H cyanation of hydroxy-, alkoxy-, and benzyloxyarene derivatives has been introduced, using nontoxic potassium thiocyanate as a cyanating reagent in the presence of silica sulfuric acid (SSA). The desired products are obtained in good to high yields without any toxic byproducts.}, language = {en} } @misc{KleinpeterShainyan2019, author = {Kleinpeter, Erich and Shainyan, Bagrat A.}, title = {Very low-temperature dynamic Si-29 NMR study of the conformational equilibrium of (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane}, series = {Magnetic resonance in chemistry}, volume = {57}, journal = {Magnetic resonance in chemistry}, number = {6}, publisher = {Wiley}, address = {Hoboken}, issn = {0749-1581}, doi = {10.1002/mrc.4870}, pages = {317 -- 319}, year = {2019}, language = {en} } @article{KleinpeterKoch2019, author = {Kleinpeter, Erich and Koch, Andreas}, title = {Benzyne - an acetylene- or cumulene-like electronic structure?}, series = {Tetrahedron}, volume = {75}, journal = {Tetrahedron}, number = {33}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2019.07.011}, pages = {4663 -- 4668}, year = {2019}, abstract = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzyne 1 and analogues (benzene 2, 1,2,3-cyclohexatriene 3, cyclohexen-3-yne 4, cyclohexen-4-yne 5, cyclohexyne 6) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values could be employed to compare the diatropic ring current effects of benzene and benzyne, and, when compared with the spatial magnetic properties of the analogues, to answer the question whether the benzyne electronic structure is more acetylene- or cumulene-like, supported by structural data and delta(C-13)/ppm values. (C) 2019 Published by Elsevier Ltd.}, language = {en} } @article{KleinpeterKoch2019, author = {Kleinpeter, Erich and Koch, Andreas}, title = {Benzenium Ion}, series = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, volume = {123}, journal = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, number = {20}, publisher = {American Chemical Society}, address = {Washington}, issn = {1089-5639}, doi = {10.1021/acs.jpca.9b03121}, pages = {4443 -- 4451}, year = {2019}, abstract = {The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of the benzenium cation (C6H7+) 1 and of +/- I/M-substituted analogues C6H6X+ 3-8 [X = -Me, -CF3, -NH2, -NO2, -NO, -SiH3] have been calculated using the gauge-independent atomic orbital perturbation method employing the nucleus-independent chemical shift concept, and iso-chemical-shielding surfaces of various sizes and directions have been observed. The TSNMRS values were employed to compare the spatial magnetic properties (TSNMRS) of benzene and the benzenium ion 1 and then further compared with analogues 3-8, to answer the question whether the electronic structures of 1 and 3-8 are still similar to those of aromatic species or somewhat similar to the antiaromatic cyclopentadienyl cation 2, supported by structural data and delta(C-13)/ppm values.}, language = {en} } @article{KleinpeterKoch2019, author = {Kleinpeter, Erich and Koch, Andreas}, title = {Is the term "Carbene" justified for remote N-heterocyclic carbenes (r-NHCs) and abnormal N-heterocyclic carbenes (aNHCs/MICs)?}, series = {Tetrahedron}, volume = {75}, journal = {Tetrahedron}, number = {11}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2019.02.005}, pages = {1548 -- 1554}, year = {2019}, abstract = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of typical N-heterocyclic carbenes NHCs, r-NHCs, a-NHCs and MICs have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. Prior to that both structures and 13C chemical shifts were calculated and in case of isolated carbenes the computed δ(13C)/ppm values compared (as a quality criterion for obtained structures) with the experimental ones. The TSNMRS values of the studied carbenes, which are in mesomeric equilibrium with zwitterionic (ylide/betaine/mesoionic) resonance contributors, are employed to qualify and quantify the present electronic structure and if the term carbene is still justified to denote the compounds studied. The results, thus obtained from spatial magnetic properties (TSNMRS), are compared with the geometry of the compounds, the corresponding WIBERG's bond index values, and the 13C chemical shifts especially of the carbene electron-deficient centre.}, language = {en} } @article{KleinpeterKoch2019, author = {Kleinpeter, Erich and Koch, Andreas}, title = {The 13 C chemical shift and the anisotropy effect of the carbene electron-deficient centre}, series = {Magnetic resonance in chemistry}, volume = {58}, journal = {Magnetic resonance in chemistry}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {0749-1581}, doi = {10.1002/mrc.4979}, pages = {280 -- 292}, year = {2019}, abstract = {Both the C-13 chemical shift and the calculated anisotropy effect (spatial magnetic properties) of the electron-deficient centre of stable, crystalline, and structurally characterized carbenes have been employed to unequivocally characterize potential resonance contributors to the present mesomerism (carbene, ylide, betaine, and zwitter ion) and to determine quantitatively the electron deficiency of the corresponding carbene carbon atom. Prior to that, both structures and C-13 chemical shifts were calculated and compared with the experimental delta(C-13)/ppm values and geometry parameters (as a quality criterion for obtained structures).}, language = {en} }