TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Benzyne - an acetylene- or cumulene-like electronic structure? JF - Tetrahedron N2 - 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. KW - Benzyne-allene or cumulene-like structure KW - Trough-space NMR shieldings (TSNMRS) KW - NICS KW - Iso-chemical shielding surfaces (ICSS) KW - Ring current effect Y1 - 2019 U6 - https://doi.org/10.1016/j.tet.2019.07.011 SN - 0040-4020 VL - 75 IS - 33 SP - 4663 EP - 4668 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Kriiger, Stefanie A1 - Koch, Andreas T1 - Anisotropy Effect of Three-Membered Rings in H-1 NMR Spectra: Quantification by TSNMRS and Assignment of the Stereochemistry JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - The spatial magnetic properties (through Space NAIR shieldings, TSNMRSs) of cyclopropane; of the heteroanalogous oxirane, thiirane, and aziridine; and of various substituted dis-, and tris-cyclic analogues have been computed by the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSSs) of various size and direction. The TSNMRS values, thus obtained, can be employed to visualize the anisotropy (ring current) effect of I the cyclopropane ring moiety. This approach has been employed to qualify and quantify substituent influences and contributions of appropriate ring heteroatoms O, NH, and S on the anisotropy (ring current) effect of three-mernbered ring moieties, and to assign the stereochemistry of mono-, bis-, and tris cyclic structures containing cyclopropane as a structural element. Characteristic examples are included. Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpca.5b03078 SN - 1089-5639 VL - 119 IS - 18 SP - 4268 EP - 4276 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zborowski, Krzysztof Kazimierz A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Proniewicz, Leonard Marian T1 - Searching for aromatic celate rings. Oxygen versus Thio and Seleno Ligands JF - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics N2 - As a part of searching for fully aromatic chelate compounds, copper complexes of malondialdehyde as well as its sulfur and selenium derivatives were investigated using the DFT quantum chemical methods. Chelate complexes of both Cu(I) and Cu(II) ions wereconsidered. Aromaticity of the metal complexes studied were analyzed using NICS(0), NICS(1), PDI, I-ring, MCI, ICMCI and I-B aromaticity indices, and by TSNMRS visualizations of the spatial magnetic properties. It seems that partial aromaticityof studied chelates increases when oxygen atoms in malondialdehyde are replaced by sulfur and selenium. KW - Aromaticity KW - Chelatoaromaticity KW - Copper Metal Complexes KW - Quantum Chemical Calculations Y1 - 2014 U6 - https://doi.org/10.1515/zpch-2014-0528 SN - 0942-9352 VL - 228 IS - 8 SP - 869 EP - 878 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Michaelis, Marcus A1 - Koch, Andreas T1 - Are para-nitro-pyridine N-oxides quinonoid or benzenoid? An answer given by spatial NICS (TSNMRS) JF - Tetrahedron N2 - The spatial magnetic properties (Through-Space NMR Shieldings-TSNMRS) of a number of substituted para-nitro-pyridine N-oxides have been computed, visualized as Iso-Chemical-Shielding-Surfaces (ICSS) of various size and direction, and were examined subject to the present quinonoid or benzenoid pi-relectron distribution of the six-membered ring. (C) 2015 Elsevier Ltd. All rights reserved. KW - para-Nitro-pyridine N-oxides KW - Quinonoid structure KW - Benzenoid structure KW - Ring current effect KW - Anisotropy effect KW - Theoretical calculations Y1 - 2015 U6 - https://doi.org/10.1016/j.tet.2015.02.043 SN - 0040-4020 VL - 71 IS - 15 SP - 2273 EP - 2279 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Barta, Petra A1 - Szatmari, Istvan A1 - Fueloep, Ferenc A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Synthesis and stereochemistry of new naphth[1,3]oxazino[3,2-a] benzazepine and naphth[1,3]oxazino[3,2-e]thienopyridine derivatives JF - Tetrahedron N2 - Through the reactions of 1- or 2-naphthol and 4,5-dihydro-3H-benz[c]azepine or 6,7-dihydrothieno[3,2-c]pyridine, new aminonaphthol derivatives were prepared. The syntheses were extended by using N-containing naphthol analogues such as 5-hydroxyisoquinoline and 6-hydroxyquinoline. The ring closures of the novel bifunctional compounds were also achieved, resulting in new naphth[2,1-e][1,3]oxazines, naphth[1,2-e][1,3]oxazines, isoquinolino[5,6-e][1,3]oxazines and quinolino[5,6-e][1,3]oxazines. H-1 NMR spectra of the target heterocycles 16, 20 and 21 were sufficiently resolved to indentify the present stereochemistry; therefore, beside computed structures, spatial experimental (dipolar coupling-NOE) and computed (ring current effect of the naphthyl moiety-TSNMRS) NMR studies were employed. The studied heterocycles exist exclusively as S(14b),R(N), R(14b),S(N), and S(16b)S(N) isomers, respectively. The flexible moieties of the studied compounds prefer. (C) 2016 Elsevier Ltd. All rights reserved. KW - Modified Mannich reaction KW - Thienopyridine KW - Benzazepine KW - NMR spectroscopy KW - Stereochemistry KW - Theoretical calculations Y1 - 2016 U6 - https://doi.org/10.1016/j.tet.2016.03.058 SN - 0040-4020 VL - 72 SP - 2402 EP - 2410 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Krtitschka, Angela A1 - Krüger, Tobias A1 - Linker, Torsten T1 - NMR spectroscopic conformational analysis of 4-methylene-cyclohexyl pivalateThe effect of sp(2) hybridization JF - Magnetic resonance in chemistry N2 - The conformational equilibrium of the axial/equatorial conformers of 4-methylene-cyclohexyl pivalate is studied by dynamic NMR spectroscopy in a methylene chloride/freon mixture. At 153K, the ring interconversion gets slow on the nuclear magnetic resonance timescale, the conformational equilibrium (-G degrees) can be examined, and the barrier to ring interconversion (G(#)) can be determined. The structural influence of sp(2) hybridization on both G degrees and G(#) of the cyclohexyl moiety can be quantified. KW - 4-methylene-cyclohexyl pivalate KW - conformational analysis KW - dynamic NMR spectroscopy KW - exo-methylene conformational effect at cyclohexane KW - quantum chemical calculations Y1 - 2017 U6 - https://doi.org/10.1002/mrc.4630 SN - 0749-1581 SN - 1097-458X VL - 55 SP - 1073 EP - 1078 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Szatmari, Istvan A1 - Belasri, Khadija A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Fulop, Ferenc T1 - Ortho-Quinone methide driven synthesis of new O,N- or N,N-Heterocycles JF - ChemistryOpen : including thesis treasury N2 - 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. KW - ortho-quinone methide (o-QMs) KW - modified Mannich reaction KW - cycloaddition KW - NMR spectroscopy KW - conformational analysis KW - DFT calculations Y1 - 2019 U6 - https://doi.org/10.1002/open.201900150 SN - 2191-1363 VL - 8 IS - 7 SP - 961 EP - 971 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Benzenium Ion BT - aromatic as the pi-complex or antiaromatic as the sigma-complex being somewhat similar to the cyclopentadienyl cation JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - 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. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpca.9b03121 SN - 1089-5639 VL - 123 IS - 20 SP - 4443 EP - 4451 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Stable Carbenes or Betaines? JF - European journal of organic chemistry N2 - The anisotropy effect in H-1 NMR spectroscopy can be readily employed to indicate the position of carbene/betaine mesomeric equilibria. NR2 substituted carbene/betaines tend to adopt betaine structures, whereas in the absence of NR2 substituents, the betaine structures cannot stabilise the structure through both -donation effects of the NMe2 groups and the electronegativity of the nitrogen atoms, and the corresponding carbene-like structures are preferred. These conclusions are supported by calculated bond orders and (C-13)/ppm values. The spatial magnetic properties of isonitriles and carbon monoxide, which can be counted as stable carbenes or, at least, as carbene-analogues, also exist as stable betaine structures, which is again supported by structural and magnetic properties. KW - Carbenes KW - Betaines KW - Mesomerism KW - Through-space NMR shieldings (TSNMRS) KW - NMR spectroscopy KW - Conformation analysis Y1 - 2018 U6 - https://doi.org/10.1002/ejoc.201800462 SN - 1434-193X SN - 1099-0690 VL - 2018 IS - 24 SP - 3114 EP - 3121 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Quantification of sigma-acceptor and pi-donor stabilization in O, S and Hal analogues of N-heterocyclic carbenes (NHCs) on the magnetic criterion JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of stable O, S and Hal analogues of N-heterocyclic carbenes (NHCs) have been calculated using the GIAO perturbation method employing the nucleus-independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSSs) of various sizes and directions. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the position of the present mesomeric equilibria (carbenes <-> ylides). The results are confirmed by geometry (bond angles and bond lengths), IR spectra, UV spectra, and C-13 chemical shifts of the electron-deficient carbon centers. Y1 - 2021 U6 - https://doi.org/10.1021/acs.jpca.1c05257 SN - 1089-5639 SN - 1520-5215 VL - 125 IS - 33 SP - 7235 EP - 7245 PB - American Chemical Society CY - Washington ER -